# 3 Phase Motor Circuit Breaker Sizing Calculator

The figure we would plug into the calculator would be: (40 x 1. 25 you will get the minimum ampere for cable Third step go to cable catalogue as saudi cables and choose proper cable size If you want to select breaker flc*2. circuit breakers, or other devices specifically designed as disconnecting means shall be used for the opening, reversing, or closing of circuits under load conditions. 5mm2: 70: 140: 2. Starting a 10 hp motor (starting a motor can require 6 times more power than running a motor) may cause a single phase line to blink or have a low voltage. Circuit breaker problems like this stem from the electrical circuit itself, so the circuit breaker may not have to be replaced. DIN rail mounting (optional lugs for direct panel mounting also available). The circuit breaker is an absolutely essential device in the modern world, and one of the most important safety mechanisms in your home. Altech has been serving the Automation and Control Industry since 1984. First we have to calculate the current for that. The 3VA27 is designed for applications with the following. For example, the full-load current of a 5 HP motor at 460V is 7. Motor HP Voltage Typical Motor F. Calculations: Transformer Primary Current (Ip)= P/1. But actually there are numerous calculations are involved for determining an appropriate fuse rating. Power Factor for motor will be8. How To Calculate The Cable Size Of A Motor By Using Kw Quora 3 10 three phase feeder size schedule engineering360 electrical cable wire sizing engineering centre square d overload size chart batan vtngcf org further electrical dimensional parameters for panel boards. If I use phase values do I need to divied the power by 3 (1000/3) before using the. 19 3 Calculation of Isc values in a radial 3. This will set the pattern to be used in other cases. Molded case circuit breakers are a type of electrical protection device that is generally used for a wide range of voltages, and frequencies of both 50 Hz and 60 Hz. Enter the motor horsepower and voltage. The disconnect switch must also have the correct fuse size. You can count on Viking Electric for all your electrical supplies. Related Post: Difference between Circuit Breaker and Isolator / Disconnector Circuit Breaker Size Calculation for Continuous & Non-contentious Load. Three pumps of a pump station (30, 10, and 1 ½ horsepower) are connected to the power source of 460-volts, 3-phase. 5SL Miniature Circuit Breaker for Standard Applications in the Residential and Non-Residential Sector For all applications up to 63 A with tripping characteristics B, C, and D with a 6/10 kA switching capacity in accordance with IEC/EN 60898-1 (VDE 0641-11) 5SY Miniature Circuit Breaker. The product of the voltage and current is the apparent power and measured in VA (or kVA). 3%, 20%, and 26. Dual Element, Time Delay UL Class RK5 Fuse (Used with Properly Sized O/L Relay) Circuit Breaker (Instantaneous Trip Circuit Breaker) Continuous Amp Rating SINGLE PHASE UNITS ½ 115V 8. The three phase supply is continuous and never completely drops to zero. Conduit sizes may need to be increased if equipment grounding conductors or neutrals are also installed in the conduit. 100, accessories: auxiliary contact, voltage release. What size circuit breaker is needed for three-phase system? P = 3 x VPH x IPH x CosФ. The "size" of a circuit breaker is the maximum current that can pass through the breaker without tripping the circuit and causing a loss of power. Motor HP Voltage Typical Motor F. 5 x 8 = 140 Amps Table 430. 2 Needs of transformer short-circuit current calculation Today more than ever before, the electricity grid is developing so quickly — the power plant capacity, the substation capacity and electricity loads, as well as load density,. Trip Curve is normally plotted between the release current and tripping time (Time – Current Curve). I'm replacing two 3-phase 240v 5-ton condenser units that wererun simultaneously and were run with one 3 phase breaker (60A) with two single phase 240volt 5-ton units. For example, if a power system is designed to carry a full-load current of 2000 A, then the short-circuit capacity could be in the neighborhood of 20 * 2000 (40,000) A, or even 30 * 2000 (60,000) A. For example, if the motor is drawing 30 amps at 250 volts, you have 30 x 250 x sqrt 3 (about 1. Enter the motor sizes in the order that they will be started and select “Staggered start = Yes” below. Breaker to wire size is not always black and white. 4 14 15A 15A ½ 208V / 230V 4. Womack Data Sheet 78: Wire Size and Fuse Ratings for 3-Phase Induction Motors Download Data Sheet Motors are usually protected by both fuses (or circuit breakers) and by heater coils in a magnetic starter. *Phase converter must be new, same size, have the same features, and quality. This might also be purchased with 230v motor pulling 12A, depending on how things pan out with what fits in our various breaker panels. Sizing Motor-Circuit Feeders and Their Overcurrent Protection. The size is relatively large. Calculate size of each part of DOL motor starter for the system voltage 415V, 5HP three phase house hold application induction motor, code A, motor efficiency 80%, motor RPM 750, power factor 0. Open cable anywhere between transformer secondary and motor terminals. DS - Single Phase vs. Circuit-breaker selection for CBP duty: The s. Related Post: Smart WiFi Circuit Breaker - Construction, Installation and Working Circuit Breaker Size Calculation for Three Phase Supply. There are two types of system available in electric circuit, single phase and three phase system. Circuit breaker is sized per 430 Part IV, and the max CB size can be up to 250 % of the FLA, which is 35 Amps. What is momentary current rating of circuit breaker? How it si estimated? 16. This feeds a distribution block where the conductors step down to #1 AWG. written on the motor nameplate first if it is available. 5 mfd capacitor will not work with a 4. Three-phase voltage waveform. 25 you will get the minimum ampere for cable Third step go to cable catalogue as saudi cables and choose proper cable size If you want to select breaker flc*2. In circulating in the core they produce heat. Maximum HORSEPOWER 3 PHASE MOTORS : Full Voltage Starting: Auto Transformer Starting: Part Winding Starting: WYE - Delta Starting: NEMA SIZE: 200V: 230V: 460V 575V: 200V. Moment of inertia is the measure of an object's resistance to changes in its rotation rate. 1 Advantages of this method p. However, figuring power usage is more complicated because the conventional equation for power usage must be modified to apply to three phase motors. Anything unusual like a loud noise, mysterious humming in the breaker box or heat radiation and sparking around the circuit breaker panel is not common. 732x400) = 16. Breaker size must be rated for a minimum of 125% of the full-load current of the motor it is protecting, rounded up to the next standard breaker size. ABB is a leader in circuit protection, and ABB breakers are trusted industry wide. Select a disconnect switch with the same or greater horsepower rating as the appliance. I'm thinking of using the A-C legs to one condenser and and B-C legs to the other Assuming I don't exceed the breaker amperage, will the excess amperage on the C leg foul up the. Note! - in the calculator above FLA is RLA + 25%. In other words, the breaker controlling a circuit should be 125 percent of the continuous load (maximum current expected to last for three hours or more) and 100 percent of the non-continuous load. The impedance of the three-phase power system is 7%. If equipment terminations are rated for 60°C conductors only, the 60°C ampacities. 5V size battery. 732xVp Transformer Primary. Filter 3: If the MOP is less than 15, it shall be rounded up to 15 amps. Application - Three-Phase Motors TABLE 15 Three and Six Wire Cable, 50 Hz Service Entrance to Motor – Maximum Length in Metres 6 - Lead Star (Wye) - Delta 90°C 90°C Motor Rating Metric Cable Size, Square Millimeters, Copper Wire - 90°C Rated Insulation Volts kW HP 2. The three phase supply is continuous and never completely drops to zero. 73 x 220 volts x. So our motor power is 15KW with 15 x 1000 = 15000 Watts. Womack Data Sheet 78: Wire Size and Fuse Ratings for 3-Phase Induction Motors Download Data Sheet Motors are usually protected by both fuses (or circuit breakers) and by heater coils in a magnetic starter. Instantaneous trip circuit breakers respond to immediate (almost instantaneous) values of current from a short circuit, ground fault, or locked rotor current. 6 Amps per phase 16. The three phase electric motor is usually a large piece of equipment that uses a "polyphase" circuit to draw heavy power loads at relatively low voltages. One method to determine the Potential short circuit current if you do not have a Loop Impedance Tester. If this calculation had not conformed to a standard circuit breaker size or if the calculated circuit size did not allow the motor to start and run, there are two exceptions that immediately follow 430. SIZE of CONDUCTORS= 16 Use 3/0 CU, OR, 250 kcmil AL 17. Related Post: Smart WiFi Circuit Breaker - Construction, Installation and Working Circuit Breaker Size Calculation for Three Phase Supply. I have a single phase 10kVA transformer that is fed from two phases of a 480V 3 phase supply. Example : We want install 1 unit single phase motor. Tuning the Capacitors To fine tune your capacitors, you need to check the voltages between each phase of the motor. Circuit Breaker Ratings: A Circuit Breaker Ratings may be called upon to operate under all conditions. 6A Fan #1 5 HP FUSE 194R-NJ030P3 30A 193-E Fusible Disconnect 3. Conduit sizes may need to be increased if equipment grounding conductors or neutrals are also installed in the conduit. Per Section 430. What size instantaneous Trip Breaker will we need for Branch Short-Circuit and GFCI protection? Standard breaker is 20 Amps. 4Nm nominal torque, with working voltage of 380V 50Hz. Ohm's Law Calculator 3-Phase Delta / Wye Calculator. First we have to calculate the current for that. 6A Fan #1 5 HP FUSE 194R-NN030P3 30A Fusible Disconnect 3 Fuses Motor Protector as Manual Starter Motor 480V, 60 Hz, 3-Phase Power Supply 140M-C2E-C10 100-C09 14 AWG 7. You can count on Viking Electric for all your electrical supplies. 3 (B), NEC 240. I have not seen it yet, but was wondering what size wire should be used to run about 65' from breaker box to compressor? What size breakers are needed? He was told 10/3 wg Romex would be enough, but I was just wanting to check with some of the good guys we have here on the forum. So our motor power is 15KW with 15 x 1000 = 15000 Watts. Motor Starting Current and Voltage Drop Calculator. For example, the full-load current of a 5 HP motor at 460V is 7. Single phase to 3 phase power calculation input requirement = The square root of 3 (1. 732xVxPfxEff) Both are same. How to Calculate Main Circuit Breaker of Capacitor Bank Electrical Wire Size Table. The recommended wire size is based on using a copper wire rated 90 degrees Celsius in Raceway. Calculation : In = 20 ampere + (0. A molded case switch, rated in amperes, can serve as a motor controller. 2 The term power circuit breaker also applies to medium voltage (1000-72. 23 KV √3 Wire Size- 25. Fusing and circuit breaker protection. 5 kW and voltage of 400V, what size circuit breaker is needed for three-phase system. Motor Sizing Calculations. But since there are 2 HOT 120-volt legs at 6000 + 6000 = 12,000 watts to use in the RV or 50-amp X 240-volt = 12,000 watts when used as a 240-volt service. Size of Service and/or Feeder Conductors. older buildings, the peak demand can generally be determined from the power company or from past billings. Open fuse or open pole in circuit breaker on main, feeder, or motor branch circuit. Moving to the bottom area of the one-line, notice that the circuit breaker (b3) in the middle is connected to the bus in the. The individual circuit might just need to be repaired. Phase - Electrical phase refers to voltage, and residential electrical services are almost all single phase voltage which is the 110/220 (also 115/130 and 120/240 since voltage is a range, not a hard number) Volts that you are probably already familiar with. Primary protection only is required if the transformer is single-phase and the secondary has only two wires. Circuit Breakers We supply new, surplus and remanufactured low and medium voltage circuit breakers of all types and all manufacturers. Single phase to 3 phase power calculation input requirement = The square root of 3 (1. My calculation was 11500/(1. 250 for3 phases motor at voltage and horse power you can select flc or starting current Second step to calculat cable size: flc *1. A typical 3-phase squirrel-cage motor has six connection leads in the electrical connection box for the three coils. Motor Starting Current and Voltage Drop Calculator. How to size Circuit Breaker for Three Phase Motor? Note: This article will only cover Inverse Time Circuit Breakers as defined above. 5mm2: 128: 256: 4mm2: 205: 412. Single & Three Phase Line kVA calculator is an online tool used in electrical engineering to measure the unknown quantity by two known quantities applied to the below formulas for single phase and three phase connection. If the motor is located at 300 feet from the source, calculate its voltage drop? Solution: There are three approach in getting the current drawn of any motor. Easy online ordering for the ones who get it done along with 24/7 customer service, free technical support & more. 25A Which of the following is true concerning the starting current of an induction motor at the moment the circuit is energized?. They are minimized by cutting the core into thin layers and laminating each layer. If I use phase values do I need to divied the power by 3 (1000/3) before using the. From table 430-150, they draw 40 amps, 14 amps, and 3 amps respectively. e the current will flow through only one wire and there will be one return path called neutral line to complete the circuit. Small Business Relationships. 6 Amps per phase 16. Calculations are based on the national standard for Heating & Cooling Equipment, UL1995, a. my breakers are as follows 1-200 amp 1-150 amp 3-125 amp 3-100 amp 5-80 amp 1-50 amp 1-40 amp 1-30 amp all these add up to 1545 amps. Single Phase Motor Wiring Diagram with Capacitor Start. S is the cross sectional area of the conductor. An inverse time circuit breaker used as the disconnecting means for a 50 hp, 480-volt, three-phase continuous-duty, induction-type ac motor shall have an ampere rating of at LEAST _____. If I use phase values do I need to divied the power by 3 (1000/3) before using the. Moulded Case Circuit Breaker and Thermal Overload Relay functions integrated into a highly compact unit known as Motor Protection Circuit Breaker. Three-phase voltage systems are composed of three sinusoidal voltages of equal magnitude, equal frequency and separated by 120 degrees. While they may reduce harmonics during a ground fault, they do not add to system fault current calculations as do fixed tuned harmonic filters. Motor Horsepower Motor Ampere Size Breaker Size Starter Heater Ampere Size Wire Size Conduit 1 230V 460 V 4. Cable conductor size: Single-phase (230v) Circuit Am per %Vd: Three-phase (230v) Circuit Am per %Vd: 1mm2: 45: 90: 1. 6A Fan #1 5 HP FUSE 194R-NN030P3 30A Fusible Disconnect 3 Fuses Motor Protector as Manual Starter Motor 480V, 60 Hz, 3-Phase Power Supply 140M-C2E-C10 100-C09 14 AWG 7. You'll find a great range of ABB circuit breakers in our online catalog, whether you are looking for a molded case power distribution breaker or a miniature circuit breaker. But actually there are numerous calculations are involved for determining an appropriate fuse rating. 732, where 1. When the fault current is relatively high, it easily disconnects the upper and lower circuit breakers all of a sudden. The currents listed. Size of Service and/or Feeder Conductors. 3 Phase Wire Size Chart Beautiful Conductor Size Chart Luxury 29. 1 Amps @ 230 VAC nominal (3 phase = 3 wire connection) for the 6,000 Watt model. The recommended wire size is based on using a copper wire rated 90 degrees Celsius in Raceway. A 10 HP motor is to be installed in a 220 V, 3-phase AC system. 3 Amp so use 35A. Calculate size of each part of DOL motor starter for the system voltage 415V, 5HP three phase house hold application induction motor, code A, motor efficiency 80%, motor RPM 750, power factor 0. 5 and you will get maximum over current protection take the next. Sizing the feeder conductors Size the feeder conductors at a minimum of 125% of the motor full load current or next higher ampacity. 3 kW to 45kW with the total load of 500kW and 230V per phase. 4 15 15 0 00 7. Blog Johnson Electric Supply Company. These conditions, per UL 489, Underwriters Laboratories Standard for Safety for Molded-Case Circuit Breakers and Circuit Breaker Enclosures, include mounting the CB in free air (i. Circuit Breakers - New, Used & Obsolete. 23 KV √3 Wire Size- 25. This is from Digest 176, page 7-33, dated 2012. Size:45mm Wide x 85mm Deep x 95mm High Weight:0. My calculation was 11500/(1. Molded case circuit breakers are a type of electrical protection device that is generally used for a wide range of voltages, and frequencies of both 50 Hz and 60 Hz. Whenever electrical wiring in a building has too much current flowing through it, these simple machines cut the power until somebody can fix the problem. Siemens 3RV1935-1A Motor Starter Control Siemens Feeder Busbar Line Side 50 mm Bar Width 110 mm Bar Length 15 mm Bar Thickness 3 ph For Use With: 3RV1 Motor Starter Protector and 2 Circuit Breaker 690 VAC 108 A Additional Description: SIEM-3RV1935-1A (N) MSP S2 BUS FOR 2 NON-CANCELABLE NON-RETURNABLE Catalog Description: Modular spACing 50 mm f. Motor-protective circuit-breaker according to IEC/EN60947, 3 pole size PKZM0, with adjustable overload and non-delayed short-circuit release, phase failure sensitive, screw and snap fitting, with screw terminal, cap installation dimension 45mm, rated operating voltage Ue 690V, degree of protection IP20, finger proof according to VDE 0106 T. I have 30 hp 3 phase 120/208 motor that is for an elevator. User manuals, specification sheets, CAD drawings and more. 2 The term power circuit breaker also applies to medium voltage (1000-72. However, major duties are imposed on the Circuit Breaker Ratings when there is a fault on the system in which it is connected. This is from Digest 176, page 7-33, dated 2012. Please, tell me if i worked this out correctly, if not show me. Blog Johnson Electric Supply Company. Size:45mm Wide x 85mm Deep x 95mm High Weight:0. Moving to the bottom area of the one-line, notice that the circuit breaker (b3) in the middle is connected to the bus in the. Motor Protector as IEC Circuit Breaker Contactor Motor 400V, 50 Hz, 3-Phase Power Supply 140M-C2E-C10 14 AWG 7. Motor HP Voltage Typical Motor F. If the building is served by a 2000 amp breaker, use 1600 amp (2000 x 0. Such as #10 on a 30 amp breaker. The three phase system is also used as a single phase system. The 3 phases used by the motor are A-B-C, or also refered to L1-L2-L3. Here are the three main causes for power losses in the operation of a transformer: Eddy Currentsare local short-circuit currents induced in the iron core by alternating magnetic flux. Define short circuit interrupting MVA of a circuit breaker. It is not to be relied upon. SIRIUS 3RV27 and 3RV28 can be used according to UL 489/CSA C22. ) Once the motor is up and running, it is time to fine tune the capacitors. The consumer unit is a hager and I was wondering what size breaker What size armoured cable do I need for my summerhouse and 32amp hot tub. Fusing and circuit breaker protection. 3 phase direct on-line motors consist of three sets of windings (one for each phase), connected in delta. The steps cover motor full load currents, branch circuit sizing, branch circuit overload protection, feeder sizing, and feeder over current protection sizing for single- and three-phase, Alternating Current Motors of more than 1 horsepower. PART – B 1. 6A Fan #1 5 HP FUSE 194R-NN030P3 30A Fusible Disconnect 3 Fuses Motor Protector as Manual Starter Motor 480V, 60 Hz, 3-Phase Power Supply 140M-C2E-C10 100-C09 14 AWG 7. a 30A circuit breaker can safely carry the exact 30A current but NEC suggests 80% as a safe current limit as compared to the rated current. maximum allowable molded case circuit breaker, using current-limiting fuses in lieu of a circuit breaker may allow a smaller transfer switch to be used. Enter the motor sizes in the order that they will be started and select “Staggered start = Yes” below. Our calculator yields results that are within code in most locations however we advise you to check your local electrical code. GFI or GFCI circuit breaker (Ground fault circuit interrupter. Conduit sizes may need to be increased if equipment grounding conductors or neutrals are also installed in the conduit. 8 Amps, so i need a 50 Amp breaker. 52(C) that permit the circuit breaker to be raised to the next higher standard size (Exception No. From table 430-150, they draw 40 amps, 14 amps, and 3 amps respectively. Moving to the bottom area of the one-line, notice that the circuit breaker (b3) in the middle is connected to the bus in the. If I want to protect the transformer with a 3 phase circuit breaker, how should I size it? The full load amps of the single phase 10kVA transformer is 20. The use of single-pole circuit breakers for multiple-phase circuits is unacceptable, since only the line compromised by the fault will be cleared, and this can cause a second fault. บริษัท ฮิตาชิ อินดัสเตรียล เทคโนโลยี (ประเทศไทย) จำกัด ผลิตมอเตอร์, Gear motor, Vortex blower, Circuit breaker และ Magnetic contactor เพื่อใช้ในอุตสาหกรรม. This load center is built with a shielded, copper bus bar that is plated for reliability. 0 for 3 wire single phase AC or DC 3. Small Business Relationships. Also Calculate Size of Overload Relay if O/L Relay Put in the wingdings (overload is placed after the Winding Split into main and delta Contactor) or in. However, this rarely happens. The wire size from the auxiliary capacitor bank to the 3 PH motor may be determined by the following formula which will calculate the amperage rating of the circuit. my breakers are as follows 1-200 amp 1-150 amp 3-125 amp 3-100 amp 5-80 amp 1-50 amp 1-40 amp 1-30 amp all these add up to 1545 amps. If equipment terminations are rated for 60°C conductors only, the 60°C ampacities. Filter 3: If the MOP is less than 15, it shall be rounded up to 15 amps. 5 kV) breakers. Multiple motors started at the same time may be summed and treated as one motor. S is the cross sectional area of the conductor. When sizing branch-circuit short-circuit and ground-fault protection for a motor, use the current values given in tables 430. I'm replacing two 3-phase 240v 5-ton condenser units that wererun simultaneously and were run with one 3 phase breaker (60A) with two single phase 240volt 5-ton units. The tables below are intended to be a general guide for AC motor Full Load Amperes. If aluminum wire is used, it must be two sizes larger than copper wire and oxidation inhibitors must be used on connections. For example, if a power system is designed to carry a full-load current of 2000 A, then the short-circuit capacity could be in the neighborhood of 20 * 2000 (40,000) A, or even 30 * 2000 (60,000) A. Conventional method A method using Motor circuit breaker (Released at the same time, New MS-T Series) A Motor circuit breaker is a device integrating Low voltage circuit breakers and Thermal Overload Relays functions. 5 and you will get maximum over current protection take the next. Note: If the motor doesn't start on a 20 Amp breaker you can go up to 800% of full load current. If this calculation had not conformed to a standard circuit breaker size or if the calculated circuit size did not allow the motor to start and run, there are two exceptions that immediately follow 430. 732, where 1. From there I supply each of 4 distribution blocks, 1 for each pair of doors. Motor Control Circuit Wiring S Bharadwaj Reddy August 1, 2017 October 5, 2018 A simple three-phase, 480 volt AC motor-control circuit is shown here, both in pictorial and schematic form. Conduit sizes may need to be increased if equipment grounding conductors or neutrals are also installed in the conduit. When an object is just sitting without any motion, the moment of inertia is 0. Choose the cable size whichever is greater in step 1 or step 2. motor calculator. I have a main disconnect for 3 phase 460VAC with 350 Amp fuses. I'm thinking of using the A-C legs to one condenser and and B-C legs to the other Assuming I don't exceed the breaker amperage, will the excess amperage on the C leg foul up the. First we have to calculate the current for that. Usually when I see a 240v device, it is wired to its own double-pole circuit breaker, with each pole connected to a different 120v phase (to provide 240v total). Phase - Electrical phase refers to voltage, and residential electrical services are almost all single phase voltage which is the 110/220 (also 115/130 and 120/240 since voltage is a range, not a hard number) Volts that you are probably already familiar with. The "size" of a circuit breaker is the maximum current that can pass through the breaker without tripping the circuit and causing a loss of power. Remember the fuse and breaker are there to protect your cabling from overheating (and potentially catching fire). One half of the copper is required and the wire transmission losses will be halved. The use of single-pole circuit breakers for multiple-phase circuits is unacceptable, since only the line compromised by the fault will be cleared, and this can cause a second fault. A how to guide for the Power Circuit of a 3 Phase Direct On Line DOL Electric Motor Controller In the simplest method of motor operation for small size AC induction motors, the Direct On Line (DOL) motor controller is most popular in terms of simplicity and control device availability. They also protect circuits downstream from the transformer. S is the cross sectional area of the conductor. 4 Calculation example p. These trends lead to new applications and market requirements that ABB SACE low-voltage circuit breakers are able to satisfy with high quality, accuracy and reliability. This is from Digest 176, page 7-33, dated 2012. While new daily cases would likely increase once activities resume, the Government will continue to detect and contain cases quickly to prevent new clusters. The actual. 3-calculate the actual impedance between the known supply to the point of fault at which near to circuit breaker. line side feeder type; sirius size s2 3rv2 series motor starter protector/circuit breaker used on; 3 phase(s); 690 volt voltage rating; 108 amp current rating; 55 millimeter spacing; 2 connection(s); rohs compliant. Make special note of the series L-C connection through zero sequence neutral path. 0 for 4 wires, 3 phase AC E - voltage between the neutral and live wire or between two live wires if no neutral line exists I - Current in any live wire except Neutral Line pf - power factor N - efficiency 2. 4 Equations for the various currents p. Power System:Base load and Peak Load on Power Station,Diesel Power Station,Electrical Energy,Energy Efficiency,Gas Turbine Power Plant,Hydroelectric Power. 5mm2: 128: 256: 4mm2: 205: 412. 8 NEC 310-16 Use #8 good for 45 amp, 3 #8 + 1 #8 ground in 1" RGC Table 3A Circuit Breaker = 25. Circuit Breaker = 5. If i have a power of 11. Conduit sizes are for three conductors per circuit for three phase motors and two conductors per circuit for single phase and DC motors. The National Electrical Code requires inverse time circuit breakers to be sized to a maximum of 250% of the motor FLA. 5 and you will get maximum over current protection take the next. The copper THHN circuit conductors are routed in an area with an ambient temperature not exceeding 104°F, and the number of current-carrying conductors in the raceway is three. 50-amp X 120-volt = 6000 watts. For example, the full-load current of a 5 HP motor at 460V is 7. The use of single-pole circuit breakers for multiple-phase circuits is unacceptable, since only the line compromised by the fault will be cleared, and this can cause a second fault. If the motor is located at 300 feet from the source, calculate its voltage drop? Solution: There are three approach in getting the current drawn of any motor. 5V size battery. Three pumps of a pump station (30, 10, and 1 ½ horsepower) are connected to the power source of 460-volts, 3-phase. Sizing Motor-Circuit Feeders and Their Overcurrent Protection. FORKLIFT – White mod. The branch-circuit short-circuit protection (dual-element fuse) for a 5-hp, 230V, single-phase motor shall not exceed 50A. Type of motor (three phase induction motor) If it’s kW, try to convert to HP with this conversion. Dual Element, Time Delay UL Class RK5 Fuse (Used with Properly Sized O/L Relay) Circuit Breaker (Instantaneous Trip Circuit Breaker) Continuous Amp Rating SINGLE PHASE UNITS ½ 115V 8. Because this is a three-phase motor, look in Table 430. I'm looking to run power from my consumer unit out to my shed. 3-Phase AC Motor F. Calculations: Transformer Primary Current (Ip)= P/1. breaking capacity (Icu) required for these circuit-breakers is given in the Figure H46 as 56 kA. 5 kW and voltage of 400V, what size circuit breaker is needed for three-phase system. For 3 phase, you will need up to 50 amp breaker depending on its voltage. How to size Circuit Breaker for Three Phase Motor? Note: This article will only cover Inverse Time Circuit Breakers as defined above. This is why 240 volt circuits connect to double pole breakers that are essentially two single pole breakers tied together. 5mm2: 128: 256: 4mm2: 205: 412. Reversing With Motor Circuit Switch. Moment of inertia is the measure of an object's resistance to changes in its rotation rate. 1) or to an even larger size (Exception No. Phase - Electrical phase refers to voltage, and residential electrical services are almost all single phase voltage which is the 110/220 (also 115/130 and 120/240 since voltage is a range, not a hard number) Volts that you are probably already familiar with. This feeds a distribution block where the conductors step down to #1 AWG. The duty cycle of the welders is 5%. 25 x Iz) In = ampere rating Iz = Load ampere. Motor HP: ½ ¾ 1 1½ 2 3 5 7½ 10 15 20 25 30 40 50 60 75 100 125 150. Allowable Voltage Drop. 25 you will get the minimum ampere for cable Third step go to cable catalogue as saudi cables and choose proper cable size If you want to select breaker flc*2. 732, where 1. Remember the fuse and breaker are there to protect your cabling from overheating (and potentially catching fire). 732x400) = 16. 3 and NEC 240. You can count on Viking Electric for all your electrical supplies. Anything unusual like a loud noise, mysterious humming in the breaker box or heat radiation and sparking around the circuit breaker panel is not common. If you have a 120V coil, instead of running a line from Coil - Overload - L2 , you must run Coil - Overload - Neutral. Example 17. A simplified method of calculation will allow a facility engineer or electrician the ability to estimate short circuit capacity. Hi, i'm a little confused about the way to calculate the amp of the circuit breaker for a three-phase system. Leverage Watlow's growing toolkit of calculators, equations, reference data and more to help design your thermal system. For Example: If the circuit is likely to draw 15 amps, you will need to install a 20 amp circuit. User manuals, specification sheets, CAD drawings and more. In the main panel, every other breaker is out of phase with the adjoining breakers. The "size" of a circuit breaker is the maximum current that can pass through the breaker without tripping the circuit and causing a loss of power. Load: Unit Heater 10 KW, 230V, 3 phase, find I, wire size, circuit breaker size Conduit Size I = 10 KW = 25. What size instantaneous Trip Breaker will we need for Branch Short-Circuit and GFCI protection? Standard breaker is 20 Amps. Circuit Breaker for Motor Protection, Size S0,130A,690V, 3RV2 Series Supply Terminal for 3-Phase Busbar, 3-Phase, Top, Size S00/S0, 3RV2 Series. Berkeley Electronic Press Selected Works. Its on a 45m run from the supply board which will house the breaker supplying it. You can count on Viking Electric for all your electrical supplies. Calculation : In = 20 ampere + (0. Calculate three-phase motor power consumption by multiplying amps by volts by the square root of three (W = AV(sqrt 3). Comparision of Short Circuit Calculation Methods. Power Factor for motor will be8. If the voltage drops considerably, the wire size is too small. If your heat pump said 3 phase on the nameplate, this would be a common voltage used in. Berkeley Electronic Press Selected Works. three phase. 11 February 2010 07:58 PM. Short circuit calculation. Siemens 3RV1935-1A Motor Starter Control Siemens Feeder Busbar Line Side 50 mm Bar Width 110 mm Bar Length 15 mm Bar Thickness 3 ph For Use With: 3RV1 Motor Starter Protector and 2 Circuit Breaker 690 VAC 108 A Additional Description: SIEM-3RV1935-1A (N) MSP S2 BUS FOR 2 NON-CANCELABLE NON-RETURNABLE Catalog Description: Modular spACing 50 mm f. i do understand the above post that says the size of the breaker tells me nothing about the load it is actually carrying. Provides short-circuit (magnetic) and motor overload (thermal) protection for a standard AC Motor. : with no enclosure) where the ambient temperature is held at 40 [degrees] C (approximately 104 [degrees] F). The tables below are intended to be a general guide for AC motor Full Load Amperes. Instead of just circuit breakers, the rack has a solid state electronic dimmer with its own circuit breaker for each stage circuit. The Motor Wire Size Calculator will calculate the proper wire size for a given motor HP and voltage. The maximum current per 3 phase leg appears to be 3 x 9. Choose the cable size whichever is greater in step 1 or step 2. One method to determine the Potential short circuit current if you do not have a Loop Impedance Tester. Many specifications call for a drive that will re-start when the driven motor is still spinning. The impedance of the three-phase power system is 7%. Our calculator yields results that are within code in most locations however we advise you to check your local electrical code. Single phase to 3 phase power calculation input requirement = The square root of 3 (1. 75 amperes Battery back-up exit lighting shall receive power from _____. Easy online ordering for the ones who get it done along with 24/7 customer service, free technical support & more. 732) x 10 amps = 1. The main distinctions between molded-case and miniature circuit breaker are that the MCCB can have current ratings of up to 2,500 amperes, and its trip settings are usually adjustable. Size:45mm Wide x 85mm Deep x 95mm High Weight:0. I= P(W) / (Voltage * Power factor). The output of the motor drive is 3-phase pulse width modulation (PWM) ranging in possible operation frequencies from 0Hz to 13kHz. The tables below are intended to be a general guide for AC motor Full Load Amperes. Breaker size must be rated for a minimum of 125% of the full-load current of the motor it is protecting, rounded up to the next standard breaker size. Circuit Breaker = 5. Set-Point Frame Size 1 Frame Size 2 Frame Size 3 Minimum 100 A 100 A 400 A Maximum 1200 A 1200 A 1200 A phase load on 3200A frame circuit breakers and below, or. motor calculator. For example, if a power system is designed to carry a full-load current of 2000 A, then the short-circuit capacity could be in the neighborhood of 20 * 2000 (40,000) A, or even 30 * 2000 (60,000) A. 277/480 although all the breakers are 3 phase. The branch-circuit short-circuit protection (dual-element fuse) for a 5-hp, 230V, single-phase motor shall not exceed 50A. my breakers are as follows 1-200 amp 1-150 amp 3-125 amp 3-100 amp 5-80 amp 1-50 amp 1-40 amp 1-30 amp all these add up to 1545 amps. 3-Phase AC Motor F. 25 = 10 Amps. From there I supply each of 4 distribution blocks, 1 for each pair of doors. Cable connectors not of the load break type, fuses, terminal lugs, and cable splice connections may not be used for such purposes, except in an emergency. Calculating the correct size Circuit Breaker to attach your wiring to is easy if you follow our guidelines shown in the chart below. This is from Digest 176, page 7-33, dated 2012. The short circuit capacity of the cables is calculated according to AS/NZS 3008 as: \(I^2t = K^2S^2\) Where: I is the short circuit current capacity in amperes, t is the short circuit duration in seconds. Instantaneous Trip Circuit Breakers. Define short circuit interrupting MVA of a circuit breaker. The currents listed. hd switch, nema 1 enclosed. Choosing a correct size for a dedicated appliance circuit involve fairly simple arithmetic to make sure that appliance's electrical demand is well within the capacity of the circuit. 100˜ 1A 1A 1A 1A 1A 1A 100˜ 100˜ v 1 v 2 v 3 Figure 3. 6A Fan #1 5 HP FUSE 194R-NN030P3 30A Fusible Disconnect 3 Fuses Motor Protector as Manual Starter Motor 480V, 60 Hz, 3-Phase Power Supply 140M-C2E-C10 100-C09 14 AWG 7. I'm replacing two 3-phase 240v 5-ton condenser units that wererun simultaneously and were run with one 3 phase breaker (60A) with two single phase 240volt 5-ton units. 52 based on the full load current and motor size. For example, the full-load current of a 5 HP motor at 460V is 7. 25) + 14 + 3 = 50 + 14+ 3 = 67 amps. The Multi-Ministry Taskforce announced on 19 May 2020 that Singapore will exit the Circuit Breaker when it ends on 1 June, and embark on a three-phased approach to resume activities safely. 5 kW) are uncommon. The table will give you the size of the short circuit protection as a percentage of the full load current. 35 do not apply to panelboards feeding and communication circuits. The last piece of electrical equipment in the middle portion of the diagram is another circuit breaker (b3). Motor-protective circuit-breaker according to IEC/EN60947, 3 pole size PKZM0, with adjustable overload and non-delayed short-circuit release, phase failure sensitive, screw and snap fitting, with screw terminal, cap installation dimension 45mm, rated operating voltage Ue 690V, degree of protection IP20, finger proof according to VDE 0106 T. Maintain Single to 3 Phase Converter w/ Circuit Breaker Box, manual, and all wiring. 8 , Overload Relay of Starter is Put before Motor. Locate where your motor falls in table 430. Per Section 430. However, this rarely happens. breaker cat no. 6 Amps per phase 16. If aluminum wire is used, it must be two sizes larger than copper wire and oxidation inhibitors must be used on connections. The following calculators can be used to calculate the motor starting voltage drop and starting inrush current of 3 phase induction motor using infinite source assumption as well when electric utility source impedance data is available. Once the circuit breaker opens or "trips" due to a short circuit or some other overcurrent scenario, the circuit. 4-Balanced three-phase fault. Also, in 3 phase the conductors need only be 75% the size of conductors for single. 5 sqmm (rated 30 amps by NEC ) to maintain the coordination of cable and the circuit breaker. The breaker must be sized for 7. Motor Sizing Calculations. One machine has a 5 HP motor, 480V three phase, about 6A. A sample of 120 volts, single phase, copper wire, 144 feet (one half of a 288 foot circuit) with 10 amps load on it yields a number 10 awg wire size. Instantaneous trip circuit breakers respond to immediate (almost instantaneous) values of current from a short circuit, ground fault, or locked rotor current. Motor HP Voltage Typical Motor F. Per Section 430. The recommended wire size is based on using a copper wire rated 90 degrees Celsius in Raceway. hd switch, nema 1 enclosed. If the motor is located at 300 feet from the source, calculate its voltage drop? Solution: There are three approach in getting the current drawn of any motor. 73 x 220 volts x. The 3VA27 molded case circuit breaker Overview Page 37 05/3/2019 EM LP Depending upon the application, the 3VA27 molded case circuit breaker takes over the line/motor/starter protection within the low voltage power distribution and provides a supplement to the existing 3VA IEC portfolio. (I2) = the current at which the CB opens. 732x400) = 16. GE and Hotpoint gas dryers (includes unitized washer/gas dryer models): Requires a 120 volt individual, properly grounded branch circuit with a 3 prong grounding type receptacle, protected by a 15 or 20 amp circuit breaker or time-delay fuse. Under fault conditions, a circuit breaker is required to perform the following three duties :. 5 4 6 10 16 25 35 50 70 95 120 150 185 240 300 400 415v 50Hz 3Ø 3-Lead. 2 Symmetrical components p. 8 Amps, so i need a 50 Amp breaker. Motor HP Voltage Typical Motor F. 32 Bibliography p. 23 KV √3 Wire Size- 25. My calculation was 11500/(1. 2 14 8A / 7A 7A ¾. 15 when starting current is not a problem. Use our helpful product filters to narrow down our extensive ABB circuit breaker catalog. The product of the voltage and current is the apparent power and measured in VA (or kVA). 732) x 10 amps = 1. Related Post: Difference between Circuit Breaker and Isolator / Disconnector Circuit Breaker Size Calculation for Continuous & Non-contentious Load. 249 and 430. Whenever electrical wiring in a building has too much current flowing through it, these simple machines cut the power until somebody can fix the problem. For further examples of connecting Heaters to lower voltages please see the chart that has been worked out on the back of this page. Lastly we will address battery inter-ties, and connections to inverters. Conductor Size: Motor branch-circuit short-circuit and ground-fault protection (percentage of FLA from Tables 430. Enter the motor sizes in the order that they will be started and select "Staggered start = Yes" below. Use of Motor Protection Circuit Breakers with Variable-Frequency Drives Introduction A motor branch circuit, including a Variable Frequency Drive (VFD ) and one or more Motor Protection Circuit Breakers (MPCBs), is a complex system and its performance depends on all co mponents, devices, configuration and their interconnection. Breaker Size. 732xVp Transformer Primary. Fault calculations provide information on currents and voltages of a power system during fault conditions. Instantaneous Trip Circuit Breakers. The power taken by a circuit (single or three phase) is measured in watts W (or kW). 4 Equations for the various currents p. Per Section 430. Many specifications call for a drive that will re-start when the driven motor is still spinning. The steps cover motor full load currents, branch circuit sizing, branch circuit overload protection, feeder sizing, and feeder over current protection sizing for single- and three-phase, Alternating Current Motors of more than 1 horsepower. : with no enclosure) where the ambient temperature is held at 40 [degrees] C (approximately 104 [degrees] F). 8 NEC 310-16 Use #8 good for 45 amp, 3 #8 + 1 #8 ground in 1" RGC Table 3A Circuit Breaker = 25. Cable Sizing Software - select, size and manage your power cables using myCableEngineering. Hi, i'm a little confused about the way to calculate the amp of the circuit breaker for a three-phase system. Size:45mm Wide x 85mm Deep x 95mm High Weight:0. The use of single-pole circuit breakers for multiple-phase circuits is unacceptable, since only the line compromised by the fault will be cleared, and this can cause a second fault. The copper THHN circuit conductors are routed in an area with an ambient temperature not exceeding 104°F, and the number of current-carrying conductors in the raceway is three. Sizing CT's. The branch-circuit short-circuit protection (dual-element fuse) for a 5-hp, 230V, single-phase motor shall not exceed 50A. The information is altered for processing and to display in a predetermined format. With a fluke meter we recorded peak currrents of 200A, 422A, and 448A, none of which were close to the minimum 1100A instantaneous trip. 3-Phase AC Motor F. Install not more than (≤) six sets of fuses or circuit breakers in series with the hot (ungrounded) service entrance wires. For instance, a motor can be severely damaged if only one of the phases is disconnected: all three must be disconnected if there is a fault. Locate where your motor falls in table 430. GFI or GFCI circuit breaker (Ground fault circuit interrupter. Circuit protection devices come in many forms, including fuses, miniature circuit breakers, molded case circuit breakers, supplementary protectors, motor protection circuit breakers, overload relays, electronic fuses, and air circuit breakers. Full Load Amps (FLA) Wire Size; PowerPact Breaker Size; PowerPact Breaker Cat No. How do I convert this into a total connected load figure for this panel and would that (along with 25% of my largest motor) be the basis for sizing my feeder and main breaker? The system is 120/208, 3 phase, 4 wire. PART – B 1. Easy online ordering for the ones who get it done along with 24/7 customer service, free technical support & more. If i have a power of 11. Also Calculate Size of Overload Relay if O/L Relay Put in the wingdings (overload is placed after the Winding Split into main and delta Contactor) or in. Obsolete, New & Used Circuit Breakers - Cutler Hammer Westinghouse & More. I'm thinking of using the A-C legs to one condenser and and B-C legs to the other Assuming I don't exceed the breaker amperage, will the excess amperage on the C leg foul up the. Conductor Size: Motor branch-circuit short-circuit and ground-fault protection (percentage of FLA from Tables 430. One machine has a 5 HP motor, 480V three phase, about 6A. Leverage Watlow's growing toolkit of calculators, equations, reference data and more to help design your thermal system. 73) = 12,975 watts). Panelboards for this application must be so marked. I should also add that if the motor is VFD driven, typically a standard breaker is used to protect the VFD and the VFD is programmed to protect the motor. The load can be measured in either amp or watts, and it is fairly easy to calculate based on the information printed on the appliance motor specification label. In three phase system power can be drawn either in a star or delta configuration. You’re preparing to drive a three phase low-horsepower motor rated at 10 amps. Line Voltage Control three phase (3ph) motor starter controlling a three phase motor (rev 08 Aug 2006) The above wiring diagram assumes your magnetic starter has a 240V coil. However, this rarely happens. Any loose connection present inside the motor terminal block. The price is relatively higher; Some circuit breakers have low breaking capacity. NEC 220-22. Cable Sizing Software - select, size and manage your power cables using myCableEngineering. Used: for Three Phase circuit; 3 Pole with Neutral (TPN (3P+N) MCB): A TPN MCB, has switching and protection to all three phases of circuit and additionally Neutral is also part of the MCB as a separate pole. Note! - in the calculator above FLA is RLA + 25%. 250 for3 phases motor at voltage and horse power you can select flc or starting current Second step to calculat cable size: flc *1. If equipment terminations are rated for 60°C conductors only, the 60°C ampacities. Moment of Inertia. Use our helpful product filters to narrow down our extensive ABB circuit breaker catalog. Two pole circuit breakers with a tie handle and. Allowable Voltage Drop. How to size Circuit Breaker for Three Phase Motor? Note: This article will only cover Inverse Time Circuit Breakers as defined above. In all cases, knowledge of the three phase bolted fault value is wanted and needs to be singled out for independent treatment. Enter the motor sizes in the order that they will be started and select “Staggered start = Yes” below. If the motor is located at 300 feet from the source, calculate its voltage drop? Solution: There are three approach in getting the current drawn of any motor. If the motors are all started together select “Staggered start = No". How to Size an Overcurrent Device for a Transformer. Single-Phase control boxes without line contactors may be connected at any point in the total cable length. See full list on electrical-engineering-portal. Price \$2720. Tuning the Capacitors To fine tune your capacitors, you need to check the voltages between each phase of the motor. 3 Amp so use 35A. Also, in 3 phase the conductors need only be 75% the size of conductors for single. Calculate size of each part of DOL motor starter for the system voltage 415V, 5HP three phase house hold application induction motor, code A, motor efficiency 80%, motor RPM 750, power factor 0. Initially I thought phase imbalance (hence other post) but I realized that would only appear in the electronic trip. The output of these transformers is given to the relays. 732x400) = 16. 6, individual single-pole circuit breakers with identified handle ties shall be permitted as the protection for each ungrounded conductor. See full list on myelectrical. (If you plan to run your TEMCo Phase Converter on a single phase generator, be sure to size your generator at three times the KW of the size of phase converter to accommodate the phase converter's inrush current. An appliance requiring a 30-amp double circuit breaker will need a disconnect rated to its horsepower and will accept two 30-amp fuses. Load: Unit Heater 10 KW, 230V, 3 phase, find I, wire size, circuit breaker size Conduit Size I = 10 KW = 25. Running on a 220v or 30 amp welder plug, you will need a 4 prong or a 3 prong heavy duty outlet. So to say #12 on a 30 amp breaker is wrong, is, well, wrong. Am I correct in thinking that a three-phase breaker should be rated based on the average of the phase currents (59. For a single-phase AC integral transformer welding gun, the equivalent three-phase AC current draw during welding is 170 amperes. This is from Digest 176, page 7-33, dated 2012. Whats people lookup in this blog: 3 Phase Circuit Breaker Sizes Table. This calculator will also give you motor amps and recommended breaker size, starter size, heater size and conduit size. Three-phase motors also vibrate less and hence last longer than single-phase motors of the same power used under the same conditions. Breaker size must be rated for a minimum of 125% of the full-load current of the motor it is protecting, rounded up to the next standard breaker size. I have 30 hp 3 phase 120/208 motor that is for an elevator. The individual circuit might just need to be repaired. 3 Phase Wire Size Chart Beautiful Conductor Size Chart Luxury 29. Calculation : In = 20 ampere + (0. Size:45mm Wide x 85mm Deep x 95mm High Weight:0. Many specifications call for a drive that will re-start when the driven motor is still spinning. Conduit sizes are for three conductors per circuit for three phase motors and two conductors per circuit for single phase and DC motors. A 90kW, 3 phase 480V uncoupled motor is tripping the magnetic overload. Wire Size Calculator; 430-148 (single-phase) 430-150 (3-phase) Table 430-148 (From 1999 NEC) The voltages listed are rated motor voltages. 3 Calculation as defined by IEC 60909 p. This tool will help you calculate the load on a circuit to see if it is excessive. Single-Phase control boxes without line contactors may be connected at any point in the total cable length. Power Factor for motor will be8. For a three-phase MFDC welding gun, the equivalent three-phase current draw during weld is 150 amperes. The impedance of the three-phase power system is 7%. Calculation : In = 20 ampere + (0. One method to determine the Potential short circuit current if you do not have a Loop Impedance Tester. 3 Phase Wire Size Chart Beautiful Conductor Size Chart Luxury 29. How To Calculate Cable Size For Motor Cable Size For Load Cable Size For 3 Phase Motor. Below is the formula to calculate the voltage drop of an electrical circuit based on the. line side feeder type; sirius size s2 3rv2 series motor starter protector/circuit breaker used on; 3 phase(s); 690 volt voltage rating; 108 amp current rating; 55 millimeter spacing; 2 connection(s); rohs compliant. The currents listed. These motors are connected directly to either a 3 phase switch or a contactor (as a method of control). Big Business Reliability. Asper nec code art430 First go to nec430. Motor HP Voltage Typical Motor F. The other two have 3/4 hp three phase 230v 3A or so. P = √3 x VL x IL x CosФ. For instance, a motor can be severely damaged if only one of the phases is disconnected: all three must be disconnected if there is a fault. 6 Amps per phase 16. If a circuit breaker or safety switch is to be used to protect a motor, the attached table has information to help you select the proper size. GFI or GFCI circuit breaker (Ground fault circuit interrupter. 32 Bibliography p. Double pole circuit breaker-This is used for 220 V. Motor Data Slide Chart. The other two have 3/4 hp three phase 230v 3A or so. I need to install circuit breaker on 3 Phase Motor ( 30 KW). 52 based on the full load current and motor size. The output of these transformers is given to the relays. Moment of inertia is the measure of an object's resistance to changes in its rotation rate. The National Electrical Code requires inverse time circuit breakers to be sized to a maximum of 250% of the motor FLA. The 4 th pole in the switch is used in the control circuit. Allowable Voltage Drop. Two pole circuit breakers with a tie handle and. Conductors are sized by the amperage that the load draws. 3 Insulated case power circuit breakers,. Conduit sizes may need to be increased if equipment grounding conductors or neutrals are also installed in the conduit. Open fuse or open pole in circuit breaker on main, feeder, or motor branch circuit. Define short circuit interrupting MVA of a circuit breaker. How do I convert this into a total connected load figure for this panel and would that (along with 25% of my largest motor) be the basis for sizing my feeder and main breaker? The system is 120/208, 3 phase, 4 wire. To find the breaker size for three phase supply voltage, we must know the exact kind of load as there are many factors affecting the load current. It acknowledges three (3) design versions, all. For three phase motor amps calculation the below formula is used. These conditions, per UL 489, Underwriters Laboratories Standard for Safety for Molded-Case Circuit Breakers and Circuit Breaker Enclosures, include mounting the CB in free air (i. If 480V three phase motor control center feeds a 50Hp motor (65a) a 40hp motor (52a) and a 10hp motor (14a) the minimum feeder ampacity is 161. BREAKER SIZING E/X Simplified Method - E/X simplified procedure result may be compared with 100% of the circuit breaker KAIC rating where X/R 15 (X1/R1 for 3-phase faults) ((2X1 + Xo)/(2R1 + Ro) for SLG-faults) - If X/R is unknown, the E/X does not exceed 80% of the KAIC rating of the breaker. The three phase bolted short circuit currents are the basic reference quantities in a system study.