CEI Motor & Motor Control Inspection Flashcards

NEC Article 440 applies specifically to which type of equipment?

Answer: Air-conditioning and refrigeration equipment

NEC Article 440 covers air-conditioning and refrigerating equipment, including hermetic refrigerant motor-compressors.

When inspecting a motor control center (MCC), which grounding method is required for the MCC enclosure?

Answer: A common ground bus bonded to the enclosure

NEC 408.40 requires motor control centers to have a main bonding jumper or equipment grounding conductor connecting the grounding bus to the enclosure.

What is the purpose of a motor controller as defined in the NEC?

Answer: To govern the starting, stopping, and speed of a motor

Per NEC Article 100, a controller is a device that governs, in a predetermined manner, the electric power delivered to the apparatus it controls.

Which NEC section requires a readily accessible means to disconnect a motor from all ungrounded supply conductors?

Answer: NEC 430.102

NEC 430.102 requires a disconnecting means to be located in sight from the motor and driven machinery and to be readily accessible.

An inspector finds a 10 hp, 480V, 3-phase motor with no overload protection installed. Under NEC 430.32, the MAXIMUM allowable overload device setting for this motor (FLA = 14A) is:

Answer: 17.5 A

NEC 430.32(A)(1) allows overload protection at not more than 125% of the motor's full-load current for motors with a service factor of less than 1.15, so 14A × 1.25 = 17.5A.

When inspecting a reduced-voltage motor starter, what is the primary reason for using this type of starter?

Answer: To limit inrush current during motor starting

Reduced-voltage starters are used to limit inrush (locked-rotor) current during motor starting, reducing demand on the electrical system.