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(a) General. The high-voltage circuit for each motor shall include coordinated protection to detect and automatically interrupt motor running overcurrent (overload) and fault currents in the motor, the motor circuit conductors, and the motor controller.
EXCEPTION: Where there is a motor which is vital to operation of the plant and the motor should operate to failure if necessary to prevent a greater hazard to persons, the sensing device shall be permitted to be connected to a supervised annunciator or alarm instead of interrupting the motor circuit.
(Title 24, Part 3, Section 430-125(a).)
(b) Grounding. Motor frames shall be grounded in accordance with Article 6.
(Title 24, Part 3, Section 3-430-145.)
(c) Fault Current Protection.
(1) Fault current protection shall be provided by one or more of the following:
(A) A circuit breaker, contactor, or other device meeting the requirements of Article 21.
(B) Fuses meeting the requirements of Article 23.
(2) Fuses used for fault interruption shall be placed in each ungrounded conductor. Circuit breakers or contactors and their associated fault sensing devices shall provide protection for, and shall simultaneously disconnect, all ungrounded conductors.
(3) Fault interrupting devices in motor circuits shall not automatically reclose after trip.
(Title 24, Part 3, Section 430-125(c).)
(d) Overload Protection.
(1) Each motor shall be protected against dangerous overheating by one, or both, of the following means:
(A) A thermal protector integral with the motor.
(B) An external current sensing device.
(2) The secondary circuits of wound rotor alternating current motors, including conductors, controllers, and resistors rated for the application, shall be considered as protected against overcurrent by the motor overload protection means.
(3) Synchronous motor rotors in addition shall be protected by a motor shutdown device matched to the squirrel-cage winding short time thermal rating for starting.
(4) Operation of the overload interrupting device shall simultaneously disconnect all ungrounded conductors.
(5) Resetting of Overload Sensing Devices.
(A) Overload sensing devices shall not be automatically reset after trip unless:
1. Resetting of the overload sensing device does not cause automatic restarting of the motor.
2. No hazard to persons is created by automatic restarting of the motor and its connected machinery.
(B) When the reset for the overload sensing device is manually operated, it shall be so located as to be safely and readily accessible.
(Title 24, Part 3, Section 3-430-125(b).)
(e) Combination Protection. Combination fault interruption and overload protection shall be permitted to be provided by the same device.
(Title 24, Part 3, Section 430-125(c)(3).)
NOTE: Authority cited: Section 142.3, Labor Code. Reference: Section 142.3, Labor Code; and Section 18943(c), Health and Safety Code.
1. Editorial correction filed 11-2-83 (Register 83, No. 45).
2. Amendment filed 12-10-87; operative 1-9-88 (Register 88, No. 1).