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Five basic questions about motors
- Jan 31, 2019 -

Five basic questions about motors

3. Why should the motor not run at light load?

When the motor is running at light load, it will cause:

(1) The motor power factor is low;

(2) The motor efficiency is low.

It will cause equipment waste and uneconomical operation.

4. Why can't the motor start in a cold environment?

The motor is too long in a low temperature environment and will:

(1) Motor insulation cracking;

(2) bearing grease freezing;

(3) Wire joint solder powder.

Therefore, the motor should be stored in a cold environment and the windings and bearings should be inspected before operation.

5. Why can't a 60Hz motor use a 50Hz power supply?

When designing the motor, the silicon steel sheet is generally operated in the saturation region of the magnetization curve. When the power supply voltage is constant, lowering the frequency will increase the magnetic flux, and the excitation current will increase, resulting in an increase in the motor current and an increase in copper consumption, eventually resulting in an increase in the temperature rise of the motor. In severe cases, the motor may be burnt due to overheating of the coil.

6. Click on the soft start. Can you save energy?

The soft start energy saving effect is limited, but it can reduce the impact of starting on the power grid, and can also achieve smooth start and protect the motor unit. According to the theory of energy conservation, soft-starting not only does not save energy, but also increases energy consumption due to the addition of a relatively complicated control circuit, but it can reduce the starting current of the circuit and play a protective role.

7. Why is the leakage circuit breaker easy to trip when using the inverter?

This is because the output waveform of the inverter contains higher harmonics, and the cable between the motor and the inverter and the motor generates leakage current. This leakage current is much larger than that of the power frequency drive motor, so this phenomenon occurs.