Motor Common Fault Causes and Solutions

Update date:2018-04-19 Source:MAXGE

Motor Common Fault Causes and Solutions

Electric motors are an indispensable and important power supplier for people's production and life. In the process of using electric motors, many electric motors will experience severe heat generation. However, many times they do not know how to solve them. Any motor failure will have an impact on production. , Electrical workers must master the basic knowledge about the safe operation of asynchronous motors and the treatment of common faults, so that the hidden dangers of motor accidents can be discovered and eliminated in a timely manner to ensure safe operation.

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The common motor faults are divided into mechanical faults and electrical faults. The electrical faults include: short circuit of stator and rotor windings, open circuit, and starting equipment failure; mechanical faults include: excessive vibration, overheating of bearings, friction between stator and rotor, and Unusual noise, etc.

First, the failure of the motor at no-load start

1. Phenomenon: no sound and no rotation

deal with:

1 First use a multimeter to check the voltage at the motor terminal block. If there is no voltage or only one phase voltage, the power supply is not connected or the power supply is faulty.

2 If the three-phase voltage at the motor terminal is substantially balanced, it indicates that there is a problem with the motor stator winding wiring. The greatest possibility is that the neutral point is not connected or the lead-out line is not connected.

2. Phenomenon: After the power is turned on, the motor only buzzes but does not rotate

Remedy: The power must be disconnected immediately and then carefully search for the cause

1 Single-phase operation First check the power supply to see if it is a phase disconnection of the power supply, one fuse of the fuse is blown, and the contactor is in poor contact with one phase; in addition, check whether the stator winding lead-out line of the motor is not connected properly.

2 Check if the machine part is stuck. When this type of fault is checked before the start of the motor, it is easy to see if the motor can be rotated gently.

3 The power supply voltage is too low or the motor technology of the ▲ connection method is connected in a Y-shape and starts with a load. As long as the power supply voltage and the motor wiring are determined correctly, it can be found.

3. Phenomenon: Start the motor after power on, fuse blows quickly (or overcurrent protection action)

deal with:

1 Check that the rated current of the fuse does not match the capacity of the motor.

2 Check if the Y-connected motor is mistakenly connected to ▲.

3 The line between the motor power supply and the connection terminal has a short circuit between phases or a short circuit to ground. Disconnect the power switch, disconnect the motor terminal, and use a megohmmeter to check.

4 The motor stator winding or lead wire has a phase short-circuit or ground.

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Second, the abnormal operation of the motor

In the running of the motor, there are often some phenomena such as motor vibration, motor overload, motor noise, bearing and wire circle temperature increase, current increase and speed change. Although these abnormalities will not make the motor protection action Tripped, but has affected the safe operation of the motor. Some of the important motors that run abnormally, if they are not dealt with in time, will not only cause the motor itself to fail, but also cause major accidents such as shutdown and shutdown of the furnace.

1, the lack of phase operation of the motor

Phenomenon: The current meter indicates rising or zero; the temperature of the motor body increases, while the vibration increases, and the sound is abnormal.

Treatment: The lack of operation of the motor is the operation of the three-phase motor when the circuit is disconnected for one reason or another. The first check is whether the power supply is missing or if the motor stator circuit fails. One of the methods to prevent the lack of phase operation of the motor is to rely on the judgment of the watchman to handle it in time after the discovery. The second is to install the phase loss protector in the motor circuit.

2, motor body heating

Phenomenon: The body temperature and temperature rise of the motor during operation are significantly higher than normal operation, and the current increases.

deal with:

1 Check whether there is friction or jamming on the mechanical load.

2 Check if the mechanical load increases, and if so, reduce the load to a stable temperature.

3 Check if the motor ventilation system is faulty and reduce the load.

4 Check whether the motor phase current is balanced, and determine whether the stator winding is faulty or missing phase operation.

3, motor vibration

1 The motor is inconsistent with the mechanical center.

2 The motor rotor is not balanced.

3 motor bearing damage.

4 The motor base strength is not enough or the anchor bolt is loose.

5 The motor runs out of phase. If the motor vibration exceeds the allowable value map, stop the motor immediately.

4, the motor sound abnormal

1 motor mechanical reasons: bearing sound is not normal, such as due to lack of oil, should immediately refuel; if the bearing has been damaged, should immediately stop running.

2 Electrical reasons: Check whether the voltage and frequency are normal. Check whether the three-phase stator current is balanced. Determine if there is a disconnection phenomenon or if there is a short circuit between the two groups.

Third, the motor burns

The reasons for burning a three-phase asynchronous motor can be divided into: load, power supply, motor insulation, and phase loss.

1. Load (overload): Excessive load operation causes the motor to heat up. Or the motor starts frequently, causing the motor to overheat. This kind of burning opportunity occurs when both ends of the stator and the rotor of the motor are burnt black, and the part that burns black is relatively uniform (generally the motor has a fixed running power, which is called the rated power and the unit is watts (W), if In cases where the actual power used by the motor exceeds the rated power of the motor, this phenomenon is called motor overload.

2, power: voltage is too low plus the load under rated conditions, the current increases, the motor overheats. The power supply voltage is too high and it burns. Or the motor runs out of phase. This situation is relatively small, it is also very easy to judge, mainly traces of the line has burned.

3. Insulation: The internal insulation of the motor does not meet the standard, and there is a short circuit between the phases. Or internal wiring error. This kind of burning machine is sometimes confused with the overload burning machine. The stator and rotor will also be blackened. However, there will be obvious burning marks in the short-circuit area. For example, there will be copper crucibles and the windings will be severely burned.

Phase loss machine:

1. The motor is delta-connected: only one phase winding will be burned, and one phase winding insulation failure can be measured with a megohmmeter (rocking table).

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2, the motor is a star (Y) connection method: there are two phase windings will burn, you can use megohmmeter (rocking table) to measure the two-phase winding insulation damage to the ground.

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