When a hard-wired backup control circuit is used in conjunction with a PLC to control a motor, then the overload contact on the motor starter must be wired in series with the motor coil to provide protection for the motor under both means of control, PLC and hard-wired.

Question

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The overload contact must be wired in series with the motor coil to ensure that the motor is protected from overload conditions regardless of whether the control is via the PLC or the hard-wired backup circuit.

When a Hard-Wired Backup Control Circuit Is Used in Conjunction