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Part 10 – Overcurrent Protection for Motor Control Circuits

How to Size Short Circuit and Overload Protective Devices for Motor Control Circuit Conductors? According to 430.75(A), motor control circuit must have a disconnect. If the motor control circuit conductors…
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Motors

Part 9 – Sizing Motor Overload Protection and OCPDs

How to Size Overload Protection for 3-Phase Motors? NEC Article 430, Part III provides guidelines for sizing overload protection devices such as, overload relays, fuses and circuit breakers for motor…
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Motors

Part 8 – Sizing Motor Feeder Protection and OCPD’s Devices

How to Determine the Size of Feeder Protection Supplying Several Motors? In the previous section, we discussed sizing feeder conductors for multiple motors. This section will explain the step-by-step process…
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Motors

Part 7 – Sizing Motor Branch Circuit Protection and OCPDs

How to Select OCPDs and Right Size Breaker / Fuse for Motor Overcurrent Protection? Sizing Branch Circuit Protection for Motors The sizing of overcurrent protection devices (OCPDs) for motor branch-circuit…
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Motors

Part 6 – Sizing Motor Feeder Conductors and Cables

How to Determine the Correct Wire Size for Feeder Supplying Multiple Motors? In previous sections on motor circuit calculations, we determined conductor sizing, overcurrent protection, and overload protection with solved…
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Motors

Part 5 – Sizing Motor Branch Circuit Conductors and Cables

How to Determine the Correct Wire Size for Motor Branch Circuit? Sizing Motor Branch Circuit Conductors Sizing the conductors for motor branch circuit is selected at 125% of the motor…
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Motors

Part 4 – Calculating Locked Rotor Current (LRC) for Motors

How to Determine the Value of Locked-Rotor Current (RLC) for Induction Motors? What is Locked-Rotor Current (RLC)? Locked-rotor current (LRA) is the maximum starting current drawn by an electric motor…
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Motors

Part 3 – Understanding NEMA Motor Nameplate Data and Marking

How to Read NEMA Motor Nameplates Data Printed on It for Motor Circuits? What is NEMA? NEMA (National Electrical Manufacturers Association) is a U.S.-based trade association that develops and publishes…
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Motors

Part 2 – NEC Requirements for Motor Circuits

General Requirements for the Design, Installation, and Protection of Motors, Motor Circuits, Controllers, and Disconnects – 2023 NEC Article 430 As discussed in part 1, motor circuits differ significantly from…
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Motors

Part 1 – Motor Load Circuits: NEC Terms and Terminologies

NEC Terms and Basic Terminologies Used in Motor Load Circuits Before designing an effective motor circuit that operates as expected based on analysis and calculations, it is important to understand…
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