1. The shaft current of the motor is generated
The current in the shaft-housing-base circuit of the motor is called the shaft current.
Causes of shaft current:
1) Magnetic field asymmetry;
2) There is a wave in the supply current;
3) The manufacturing and equipment are not good, because the rotor is eccentric and the air gap is uneven;
4) There are gaps in the two semicircles of the detachable stator core;
5) The number of pieces of the stator core with fan-shaped stacking is not appropriate.
Damage: The surface of the servo motor bearing or the ball is eroded, forming point-like micropores, deteriorating the performance of the bearing, conflicting loss and heat addition, and finally forming the bearing incineration.
Prevention: 1) Eliminate pulsating magnetic flux and power supply wave (such as installing 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 end and end cover of the rolling bearing are insulated.
2. The motor generally cannot be used in plateau areas
The sea height has an adverse effect on the temperature rise of the motor, the motor capacity (high-voltage motor) and the commutation of the DC motor, and the following three aspects should be noted:
1) As the sea increases, the greater the temperature rise of the motor, the smaller the output power, but when the temperature drops with the increase of altitude is enough to compensate for the influence of altitude on the temperature rise, the additional output power of the motor can remain unchanged;
2) Anti-corona measures should be adopted when the high-voltage motor is used on the plateau, and the sea height is not conducive to the commutation of the DC motor, so it is necessary to pay attention to the selection of carbon brush materials.
3. The motor should not be operated under light load
When the motor is running at light load, it will form:
1) The motor factor power is low;
2) The efficiency of the motor is low, which will cause equipment waste and uneconomical operation.
4. The reason for the overheating of the motor
1) Excessive load;
2) Missing items;
3) Air duct blockage;
4) The low-speed operation time is too long;
5) The power supply wave is too large.
5. The work that needs to be done before the motor is put into use
1) Measure the stator, winding resistance and winding resistance to ground insulation:
The insulating cathode R should meet the following formula: R>UN/(1000+P/1000)(MΩ)
UN: Motor Winding Extra Voltage (V) P: Motor Power (KW)
For the motor with UN=380V, R> 0.38 MΩ
If the insulation resistance is low, you can:
●The motor runs no-load for 2-3h drying;
●Use 30% additional voltage of low-voltage alternating current into the winding resistance or connect the three-phase winding resistance in series with direct current baking to keep the current at 50% of the additional current;
●Hot air or heating elements are fed with a fan for heating.
2) Finishing the fan;
3) Replace the bearing grease.
6. Do not start the motor in the cold environment arbitrarily
If the motor is too long in a low temperature environment, it will:
1) Cracking of motor insulation;
2) Bearing smooth grease freezing;
3) Solder powder generation of red joints.
Therefore, the motor should be heated and stored in an icy environment, and the winding resistance and bearings should be checked during operation.
7. The reason for the three-phase current imbalance of the motor
1) Three-phase voltage unbalance;
2) Poor welding or poor contact of a phase branch inside the motor
3) Short circuit between turns of the motor winding resistance or short circuit between phases to ground;
4) Wiring fault.
8. The 60HZ motor cannot be connected to the 50HZ power supply
When the power supply voltage is constant, the decreasing frequency will add the magnetic flux and the excitation current, resulting in the addition of the motor current and the addition of copper tillage, which will eventually lead to the increase in the temperature rise of the motor, and the motor can be incinerated due to the overheating of the coil when it is severe.
9. The reason for the lack of phase of the motor
In terms of power supply: 1) Poor switch contact; 2) Disconnection of transformer or line; 3) Insurance circuit breaker.
In terms of motors: 1) The screws of the motor junction box are loose and the contact is poor; 2) Poor internal wiring welding; 3) The motor winds the blocking line.
10. The cause of abnormal vibration and sound of the motor
Mechanically: 1) The bearing is smooth and poor, and the bearing is worn; 2) Loosening of fastening screws; 3) There is debris in the motor.
Electromagnetic: 1) Motor overload operation; 2) Three-phase current unbalance; 3) phase loss; 4) Short circuit problem occurs in stator and rotor winding; 5) The cage rotor welding part is welded to form a broken strip.
11. The work that needs to be done before starting the motor
1) Measure the insulation resistance (for low-voltage motors, it should not be less than 0.5M);
2) Measure the power supply voltage, check whether the motor wiring is correct, and whether the power supply voltage meets the requirements;
3) Check whether the starting equipment is outstanding;
4) Check whether the fuse is suitable;
5) Check whether the motor grounding and zero connection are outstanding;
6) Check whether the transmission equipment is defective;
7) Check whether the motor environment is suitable, and remove flammable products and other debris.
12. The cause of overheating of the motor bearing
The motor itself: 1) the inner and outer rings of the bearing are too tightly fitted; 2) There are problems with the shape and position tolerance of parts, such as poor coaxiality of parts such as machine base, end cover, shaft, etc.; 3) Improper selection of bearings; 4) The bearing is not smooth or clean, and there are impurities in the smooth grease; 5) Shaft current.
Application: 1) The equipment of the unit is improper, such as the coaxiality of the motor shaft and the axis of the dragged equipment meets the requirements; 2) The pulley is pulled too tightly; 3) The bearing protection is not good, the smooth grease is insufficient or exceeds the service life, and the dry is deteriorated.
13. The reason for the low insulation resistance of the motor
Circumvention of moisture or water infiltration; accumulation of dust or oil on the winding; insulation aging; Damage to the insulation of the motor leads or terminal blocks
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