Motor Frequently Asked Questions

1. Why does the motor generate the shaft current?

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

Shaft current causes:

(1) magnetic field asymmetry;

(2) there is a harmonic in the supply current;

(3) manufacturing, installation is not good, due to rotor eccentric air gap caused by uneven;

(4) detachable stator core between the two semicircular gap;

(5) The number of chips in the fan-shaped stator core is not suitable.

Hazard:

So that the motor bearing surface or ball erosion, the shape of microporous, so that the bearing performance deterioration, friction loss and heat increased, and ultimately

Bearing burned.

Prevention:

(1) to eliminate pulsating flux and power supply harmonics (such as the inverter output side of the installation of AC reactor);

(2) motor design, the sliding bearing bearing and base insulation, rolling bearing outer and end cover insulation.

2, why the general motor can not be used for highland areas?

Altitude has an adverse effect on the motor temperature rise, the motor corona (high voltage motor) and the DC motor commutation. Should pay attention to the following three aspects:

(1) high altitude, the greater the motor temperature rise, the smaller the output power. But when the temperature increases with altitude increases enough to compensate for the impact of elevation on the temperature rise

, The rated output power of the motor can be constant;

(2) high-voltage motor used in the plateau to take anti-corona measures;

(3) altitude of the DC motor commutation disadvantage, pay attention to the choice of carbon brush material.

3, why should not light motor running?

When the motor is running lightly, it will cause:

(1) the motor power factor is low;

(2) low motor efficiency.

Will cause equipment waste, run uneconomical.

(1) the load is too large;

(2) lack of phase;

(3) air duct blockage;

(4) low speed running time is too long;

(5) power supply harmonic is too large.

5, why can not arbitrarily start the cold environment in the motor?

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

(1) motor insulation cracking;

(2) bearing grease freeze;

(3) wire connection solder powder.

Therefore, the motor in the cold environment should be heated to save, should be run before the winding and bearing inspection.

6, the motor three-phase current imbalance What are the reasons?

(1) three-phase voltage imbalance;

(2) the motor within a certain branch of poor welding or poor contact;

(3) motor winding inter-turn short circuit or ground, phase short circuit;

(4) Wrong wiring.

7. Why 60Hz motor can not be connected to 50Hz power supply?

The design of the motor generally makes the silicon steel sheet work in the saturation zone of the magnetization curve. When the supply voltage is constant, the decrease of the frequency will increase the magnetic flux,

Flow increases, resulting in increased motor current, copper consumption increases, eventually leading to increased motor temperature rise, serious may also be due to coil overheating and burn the motor.

8. What are the reasons for the lack of motor?

Power supply:

(1) switch bad contact;

(2) transformer or line disconnection;

(3) insurance fuse.

Motor:

(1) the motor terminal box screws loose contact bad;

(2) poor internal wiring;

(3) The motor winding is broken.

9. What are the causes of abnormal vibration and sound of the motor?

Mechanical aspects:

(1) bearing lubrication is bad, bearing wear;

(2) bearing room is too large.

(3) fastening screws loose;

(4) There are debris in the motor.

Electromagnetic aspects:

(1) motor overload operation;

(2) three-phase current imbalance;

(3) lack of phase;

(4) stator, rotor winding short circuit failure;

(5) cage rotor welding part of the welding caused by broken bar.

10. What are the causes of motor bearing overheating?

Motor itself:

(1) bearing inner and outer ring with too tight;

(2) parts and geometric tolerances are problems, such as the base, cover, shaft and other parts of the coaxial degree is not good;

(3) improper selection of bearings;

(4) poor bearing lubrication or bearing cleaning is not clean, grease inside the debris;

(5) axis current.

Use:

(1) improper installation of the unit, such as the motor shaft and the drag of the device axis coaxial degree is not required;

(2) pulley pull too tight;

(3) bearing maintenance is not good, lack of grease or more than the use of time, dry deterioration.

11. What are the reasons for the low insulation resistance of the motor?

(1) winding moisture or water intrusion;

(2) the accumulation of dust or oil on the winding;

(3) insulation aging;

(4) motor lead or wiring board insulation damage.