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How is a 3 phase overload wired for use in a single phase motor starter?

Standard 3 phase thermal overloads, such as the  LRD and LR2K  are designed to detect a current imbalance in the 3 phase supply. As a result of this, if a single phase supply is wired such that line and neutral pass through just 2 of the 3 elements the overload can trip.

To avoid this problem when using a standard overload with a single phase motor load, the wiring through the overload must be arranged so that all three elements are in the circuit. In practice the contactor is also part of this wiring recommendation as the overload will usually be directly coupled to the contactor as shown below;



Selection of the overload for use with a single phase motor is still based on the motor full load current (FLC).
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