Field Tests and Inspections for Low Voltage Motor Control Gear.

Low voltage motor control gear serves as the one of main parts of industrial and commercial electrical systems. It regulates the operation of motors that power various machinery and equipment. Regular field tests and inspections are essential to ensure the reliability, safety, and efficiency of this low voltage motor control gear.

Here’s a comprehensive guide on how to conduct thorough field tests and inspections for low voltage motor control gear:

Visual Inspection.

1. Inspect primary and auxiliary equipment for physical damage, missing parts and proper assembly.

2. Compare equipment nameplate data with one line diagram, design plans and/or starter schedule.

3. Check nameplate voltage and current ratings for breaker, contactors and fuses.

4. Compare overload heaters with motor full load current for proper size.

5. Verify component sizing versus load.

6. Check stab finger to bus tightness on draw-out cubicles.

7. Protective grounding is correctly installed and connected to main ground.

8. Remove shipping and blocking material from Motor Control Center/Switchboard.

9. Check draw-out cubicles and wire ways for cleanliness.

Mechanical Inspection.

1. Torque all accessible bolted connections.

2. Check insulators and the insulation system.

3. Inspect main bus and bus taps to switches and voltage transformers.

4. Manually operate breakers and contactors. Check for freedom of movement of all moving parts.

5. Check for main contact pressure, alignment and full contact area on contactors.

6. Check operation of door mechanical circuit breaker trip and reset linkage.

Electrical Inspection.

1. Check wiring point to point and megger.
2. Check wire markers, and that terminal block connections are secure and properly identified.
3. Megger test main bus phase to ground and phase to phase.
4. Measure bus resistance and joint contact resistance.
5. Inspect all protective relays and devices for correct operation and settings.
6. Check to see that space heaters are connected and operable.
7. Megger horizontal and vertical bus and outgoing feeder circuits.
8. Check calibration of VT’s, CT’s, voltmeters and ammeters.
9. Check rating of all fuses.
10. Verify under voltage relay trip/alarm function.
11. Verify ground fault protection for 30 horsepower motors and larger.
12. Set motor circuit protectors.
13. Check effectiveness of tripping devices.
14. Megger and high potential test contactors and circuit breakers phase to phase and phase to ground.
15. Measure the contact resistance of each power circuit breaker.
16. Measure the contact resistance of each contactor.
17. Check the Phase Rotation of the voltage on the main bus.

Plate Information.

Equipment Identification/manufacturer.
Serial number/model number.
Rated Voltage.
Rated current.
Interrupting Rating.

Tests are performed in accordance with values recommended by the Manufacturer or values in P-000.

Motor Control Center Recorded Test Data.

Items Tested.	Megger Test
	Insulation Resistance in Mega Ohms.
Phase A to Ground.
Phase B to Ground.
Phase C to Ground.
Phase A to Phase B.
Phase B to Phase C.
Phase C to Phase A.

Motor Control Center Contact Resistance.

FEEDER NO.	Breaker or Contactor No.	PHASE A Line to load Micro-Ohms	PHASE B Line to load Micro-Ohms	PHASE C Line to load Micro-Ohms

Motor Control Center Data Sheet.

Voltage Rating:______________

Device No.	Horsepower.	Full Load Current.	Motor Overload Relay Type	Rating	Feeder No.	Feeder Insulation Resistance