1). What is the purpose of an engine starter?
It allows you to start an engine gradually, limit the current draw at start-up, and protect electrical components.
Ex:
Direct starter,
Star-triangle,
Frequency inverter.
2). What does a frequency inverter do?
It allows you to vary the speed of a three-phase asynchronous motor by changing the frequency and voltage of the power supply. It is also used to improve energy efficiency and process control.
3). How do you recognize a failed three-phase asynchronous motor?
- Abnormal noise or vibration
- Overheating
- Fuse or circuit breaker that blows
- Engine not running or running with difficulty
- Unbalanced current between phases
4). What is a contactor and what is it used for in a motor system?
It is a remote-controlled electromechanical switch that allows you to start and stop a motor in a safe way. It is often combined with thermal protection.
5). What is a thermal relay?
It is a device that protects the motor from overloading. It detects abnormal heating and opens the circuit.
6). What should be checked before returning an engine to service after intervention?
- Proper cable connection
- Correct direction of rotation
- Noise-free, vibration-free, overheating
- No-load operation test
- Control of protections.
7). What does a multimeter measure for engine maintenance?
Supply voltage The continuity of the windings Insulation resistance (with a megohmmeter) Current consumption (using a clamp meter)
8). Why is the voltage imbalance between phases dangerous for a three-phase motor?
It causes excessive heating of one or more windings, reduces motor performance, and can lead to premature failure.
9). What does an engine circuit breaker do?
It protects the motor from short circuits and overloads. It combines magnetic and thermal protection.
10). What is the role of grounding in a motor system?
It allows fault currents to be redirected to earth in the event of a leak, to protect people and equipment from electric shock.
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