A few small issues that are easy to overlook about the motor?

1. Why can't general motors be used in plateau areas?

The altitude has an adverse effect on the temperature rise of the motor, the motor corona (high-voltage motor) and the commutation of the DC motor. The following three aspects should be noted:

(1) At high altitude, the greater the temperature rise of the motor, the lower the output power. But when the temperature decreases with the increase in altitude enough to compensate for the influence of altitude on temperature rise, the rated output power of the motor can be unchanged;

(2) Anti-corona measures should be taken when high-voltage motors are used on plateaus;

(3) The altitude is unfavorable for the commutation of the DC motor, so pay attention to the selection of carbon brush materials.

2. Why does the motor produce shaft current?

The current in the motor shaft---bearing seat---base circuit is called the shaft current.

reason:

(1) Asymmetrical magnetic field;

(2) There are harmonics in the power supply current;

(3) Poor manufacture and installation, uneven air gap due to rotor eccentricity;

(4) There is a gap between the two semicircles of the detachable stator core;

(5) The selection of the number of pieces of the stator core with fan-shaped stacks is inappropriate.

harm:

The surface of the motor bearing or the balls are corroded, forming dot-shaped micro-holes, which deteriorates the running performance of the bearing, increases friction loss and heat generation, and finally causes the bearing to burn. To

prevention:

(1) Eliminate pulsating magnetic flux and power harmonics (such as installing an AC reactor on the output side of the inverter);

(2) When the motor is designed, the bearing seat and base of the sliding bearing are insulated, and the outer ring and end cover of the rolling bearing are insulated.

3. Why is the motor not suitable for light load operation?

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

(1) The power factor of the motor 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?

If the motor is too long in a low temperature environment, it will:

(1) The motor insulation is cracked;

(2) The bearing grease freezes;

(3) Powdered solder on wire joints.

Therefore, the motor should be heated and 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?

Generally, the silicon steel sheet works in the saturation region of the magnetization curve when the motor is designed. When the power supply voltage is constant, reducing the frequency will increase the magnetic flux and the excitation current, resulting in an increase in the motor current, an increase in copper consumption, and ultimately an increase in the temperature rise of the motor. In severe cases, the motor may be burnt due to overheating of the coil.

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

This is because the output waveform of the inverter contains high-order harmonics, and the motor and the cable between the inverter and the motor will generate leakage current. This leakage current is much larger than when the motor is driven at the power frequency, so this phenomenon occurs.

Jessica