A synchronous motor is operating in a plant. The operator increases the DC excitation field current above the normal level. What effect will this have on the plant electrical system?
Answers
AThe motor will speed up significantly
BThe motor will act as a synchronous condenser, providing leading reactive power to correct lagging PF
CThe motor will trip the overcurrent breaker instantly
DThe motor will consume more lagging reactive power, worsening the PF
The answer and explanation are in the full bank.
This question is one of 2,831 in the paid banks. Each comes with the correct answer and the reasoning behind it, not just a mark.
Unlock for 5,000 RWFMIFOTRA exam practicealigned to NFPA 70 / IEC 60364·3 marks·Medium
More Electrical Circuits questions
- An industrial plant has a true power of 400 kW and an apparent power of 500 kVA. What is the plant power factor, and is it lagging or leading if the load is primarily induction motors?
- A facility installs a large capacitor bank at the main switchgear to improve a lagging power factor of 0.75. After installation, they notice high transient overvoltages and VFDs tripping on overvoltage during off-shift hours. What went wrong?
- A consultant recommends adding capacitors to a motor control center. What is the primary financial benefit of correcting a poor power factor in an industrial facility?
- When a system has a power factor of exactly 1.0 (Unity PF), what is the relationship between the voltage and current waveforms?
- You measure the voltage on a 3-phase wye-connected system. The line-to-line voltage is 480V. What should the line-to-neutral voltage measure?
- In a balanced 3-phase system, what is the phase angle displacement between each of the three voltage waveforms?
- A 3-phase, 4-wire wye system is supplying a heavily unbalanced lighting load. You measure 15A on Phase A, 10A on Phase B, and 0A on Phase C. Will there be current on the neutral wire?
- A 3-phase delta-connected heater has three heating elements, each with a resistance of 10 ohms. The line voltage is 480V. If one element burns out (opens), what happens to the total heat output?