How to tell if the motor is overheated?

If you ask how to judge, we won't say more. Judge it this way.

Visual inspection, if it is a suspected bad motor that has just been run, first open the motor junction box to see if the winding lead wire is burned, if it is burned, smell it again to see if there is any peculiar smell, if the smell is very strong and smelly, it can basically be said to be burned. 2.

For the instrument measurement method, first remove the connecting copper sheet on the motor wiring board, then tighten the 6 nuts, and use a multimeter R200

The files are measured U1-U2 respectively

v1-v2,w1-w2

The resistance value between the winding (when the winding lead is not broken), if the 3 resistance values are equal, it means that the winding is not broken, and there is no short circuit between turns, and then use a 500 type megohmmeter to measure the insulation resistance between the 3-phase windings (380V motor), because it is a hot state, it should be greater than 1 megaohm, if it is lower than it, it can not be used, and then measure the insulation resistance between the windings and the casing, which must be greater than the megaohm to be used, and the motor that has just been replaced must be greater than 2 megaohms before it can be used.

Look: see whether the oil seal of the end cover of the motor front bearing becomes black, under normal circumstances, because the bearing is scattered, the severe friction makes the bearing oil seal temperature rise too high and blacken. After the bearing falls apart, it causes a sweep that short-circuits the coil or passes through the shell.

And tripping. Smell: The coil will burn out due to overload or sweeping, and when you open the junction box, you will smell the burnt smell of the coil burning.

Q: If the motor is overheated, ask the user of the motor whether the mechanical equipment is overloaded or whether the transmission parts need to be updated. Like cutters, racks have a service life.

Too old and not updated will cause the motor to overload and cause overheating. Cut:"Cut:"That's the key.

It is easy to judge that the motor is burned out, but the difficult thing is to find out the cause of the motor burnout. Troubleshooting. Or the motor will burn out if it is replaced.

Personally, I summarized the reasons for the burning of the motor: phase loss, overload, coil aging, and loose bearings. There is also a lock-and-hold blockade.

1. Abnormal load and stalled.

The motor load includes the load required for the compressed gas and the load required to overcome the mechanical friction. If the pressure ratio is too large, or the pressure difference is too large, the compression process will be more difficult; Moreover, the increase in frictional resistance caused by lubrication failure, as well as the stalled rotor of the motor in extreme cases, will greatly increase the load on the motor.

2. Contactor problem.

Contactors are one of the most important components in motor control circuits.

The contactor must have a large enough area to dissipate the heat generated by the current of the load, and the contact material must be selected to prevent soldering in the case of high currents such as actuation or locked-rotor. The contactor with small specifications or poor quality cannot withstand the high current impact of compressor starting, stalled rotor and low voltage, and is prone to single-phase or multi-phase contact jitter, welding and even falling off, causing motor damage.

3. The power supply is out of phase and the voltage is abnormal.

Abnormal voltage and lack of phase can easily destroy any motor, and the motor power cord must be able to carry the rated current of the motor.

The direct cause of the motor burnout is the high temperature.

Common faults of electric motors are divided into two categories: mechanical faults and electrical faults, electrical faults include: short circuit, open circuit, and starting equipment failure of stator and rotor windings; Mechanical faults include: excessive vibration, overheating of bearings, friction between stator and rotor, and abnormal noise.

Precautions for the use of motors:

1. The metal shell of the electric machinery must have a reliable grounding device or a temporary grounding device to avoid electric shock accidents.

2. When moving the electric machinery, the power must be turned off in advance, and it must not be moved with electricity.

3. The power supply line of the electric machinery must be installed in accordance with the rules of lighting electricity, and it is strictly forbidden to connect it indiscriminately.

4. In case of failure of electric machinery, it must be powered off for maintenance, and it cannot be operated live.

5. For machinery using single-phase motors, low-voltage electric shock safety devices should be installed, and they should always be kept sensitive and reliable.

6. Machinery that has not been used for a long time or is damp should be put into trial operation before being put into normal operation. If it does not run after powering on, it must be immediately turned off for maintenance.

What causes motor heating?

Is there an overload? Is the main contact of the AC contactor not in good contact?

Overload, phase loss, poor heat dissipation, poor bearing, lack of oil, poor motor quality, unstable voltage, etc.

The reasons for the total failure of the motor are roughly as follows:

One is overload, for example, when some motors use frequency conversion speed regulation. At low rpm. The torque is larger. The current is also large. This does not dissipate enough heat. It may be easier to break.

Second, there is a lack of phase in the power supply. Poor contacting of contactor contacts.

The third is the poor performance of the bearing. Causes the speed of the motor to drop. Work like this for a long time. The temperature rise increases. It can also damage the motor.

Fourth, the motor has been repaired many times. The level of process is reduced. Causes an increase in the air gap. Eddy current losses are increased. In this way, the temperature rise increases. It can also be easily broken.

Fifth, if the original aluminum wire motor is changed to a copper wire motor. The parameter is incorrect. It is also easy to break.

That is, the load is too large and out of range.

The current is too large, causing the machine to be unbearable, or it may be that it has been burned once and has not been re-burned.

Winding the coil, the wire is connected, and it is easy to burn.

The reasons for the total failure of the motor are roughly as follows:

One is overload, for example, when some motors use frequency conversion speed regulation. At low rpm. The torque is larger. The current is also large. This does not dissipate enough heat. It may be easier to break.

Second, there is a lack of phase in the power supply. Poor contacting of contactor contacts.

The third is the poor performance of the bearing. Causes the speed of the motor to drop. Work like this for a long time. The temperature rise increases. It can also damage the motor.

Fourth, the motor has been repaired many times. The level of process is reduced. Causes an increase in the air gap. Eddy current losses are increased. In this way, the temperature rise increases. It can also be easily broken.

Fifth, if the original aluminum wire motor is changed to a copper wire motor. The parameter is incorrect. It is also easy to break.

2。Turn-to-turn short circuits or open circuits, which are relatively rare, can be detected and repaired as soon as possible to reduce costs.

3。In particular, the mechanical jam is the most likely to burn out the motor, if the power is turned off in time, most of them can avoid burning out the motor, if it is resisted for a long time, the current doubles until the motor is burned out.

4.Motor shaft failure can also burn the motor.

5.The protective device does not work.