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Motors & Generators — Texas Master Practice Questions

12 questions · 20% of the Calculations exam

Worked questions

1. A commercial building requires a backup generator to supply power to critical loads during an outage. The total load is 200kW. What is the minimum size of the generator required, according to Article 700.6 of the 2026 NEC?

  • A150kW
  • B200kW
  • 250kW
  • D300kW

Exam tip

Remember to size generators at 125% of the total load to ensure sufficient capacity.

Why C is correct

Article 700.6 of the 2026 NEC requires a generator to be sized at 125% of the total load. Therefore, the minimum size of the generator required is 250kW (200kW x 1.25). The correct answer is option C.

2. A healthcare facility has a 500kW emergency generator. What is the minimum short-circuit current rating required for the generator protection device, according to Article 690.8(C) of the 2026 NEC?

  • A100kA
  • B125kA
  • 150kA
  • D200kA

Exam tip

Generator protection devices must be sized according to the short-circuit current rating requirements specified in Article 690.8(C) of the NEC.

Why C is correct

According to Article 690.8(C) of the 2026 NEC, the generator protection device must have a minimum short-circuit current rating of 150kA for a 500kW generator. The correct answer is option C.

3. A new generator is being installed in a healthcare facility. According to the 2026 NEC, what is the minimum grounding requirement for the generator's neutral and equipment grounding conductor?

  • A8 AWG
  • 10 AWG
  • C12 AWG
  • D14 AWG

Exam tip

Always verify the NEC for specific grounding requirements for generators, as they are critical for safety in healthcare facilities.

Why B is correct

The 2026 NEC requires that the neutral and equipment grounding conductor for generators must be a minimum of 10 AWG. This ensures proper grounding for safety and to prevent electrical hazards.

4. A residential community has a 200kW generator. What is the minimum capacity required for the transfer switch, according to Article 700.6(A) of the 2026 NEC?

  • A150kW
  • 200kW
  • C250kW
  • D300kW

Exam tip

The capacity of the transfer switch must meet or exceed the generator's rating as specified in Article 700.6(A) of the NEC.

Why B is correct

According to Article 700.6(A) of the 2026 NEC, the transfer switch must have a capacity equal to or greater than the generator's rating. Therefore, the minimum capacity required is 200kW. The correct answer is option B.

5. A residential subdivision requires a new generator to be installed. The generator has a capacity of 10kW. What is the minimum conductor size required for the generator's service entrance cable, according to the 2026 NEC?

  • A10 AWG
  • 12 AWG
  • C14 AWG
  • D16 AWG

Exam tip

Always refer to the appropriate table in the NEC for conductor sizing based on the generator's capacity.

Why B is correct

The 2026 NEC Table 310.16(B)(1) specifies that for a 10kW generator, the minimum conductor size for the service entrance cable is 12 AWG. This size is suitable for a 30A circuit.

6 more in the bank

Answers and explanations for these are in the app.

  • A 200 HP, 460V, 3-phase motor is installed in a commercial building. The motor has a full-load current of 300A. According to the 2026 NEC, what is the minimum overcurrent protection rating required for this motor?
  • A 480V, 3-phase squirrel-cage motor has a full-load current of 100A. What is the minimum conductor size required for the motor circuit, according to Article 430.22(C) of the 2026 NEC?
  • A hotel is installing a new 300kW generator. What is the minimum disconnecting means required for the generator, according to Article 700.8 of the 2026 NEC?
  • A motor control center (MCC) is being installed in an industrial plant. The MCC will house a 100 HP, 480V, 3-phase motor. What is the minimum number of branch circuits required for the MCC, according to the 2026 NEC?
  • A motor control center (MCC) is designed to house several motors. What is the minimum number of disconnecting means required for an MCC, according to Article 409.14(B) of the 2026 NEC?
  • A retail store has a 20HP, 480V, 3-phase motor. What is the minimum overload protection rating required for the motor, according to Article 430.52 of the 2026 NEC?

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