The reason why the motor frequently burns out despite various protections

There are many pumps in the chemical fiber workshop, more than 1,000 units, running 24 hours a day. Almost every day, the motors burn out. They all have thermal relay protection, and the set value is the rated current on the motor nameplate. Why do they burn out so frequently? How much does the thermal relay work? Among the more than 1,000 units, from cooling fans to oil pump motors, one has to be taken in for repair every day. Is this normal? Let's see what the electrical experts think.

1. Motor burnout is related to motor temperature, which in turn is related to current and heat dissipation conditions. Thermal relays can only protect motors when the current increases significantly in a short period of time, such as severe overload, phase loss, short circuit, etc. Assuming that the motor is in a general overload for a long time, the current will not reach the protection value of the thermal relay, and the working principle of the thermal relay is to rely on the internal resistance to generate heat to produce the deformation of the bimetallic strip to achieve action. If the current value is not seriously over-high, the heat dissipation of the relay itself will cause it to not act.

In addition, even if the current does not exceed the standard, poor heat dissipation of the motor itself will cause the motor temperature to rise and burn out.

It is recommended to check the motor load and heat dissipation.

Of course, the sensitivity and reliability of traditional thermal relays are poor. It is better to use electronic protectors.

2. Thermal relays can only respond to phase loss and overload. But what about water ingress, moisture in the motor, bearing problems? Some are instantaneous and have no response time.

I specialize in repairing electric motors. Some factories buy cheaper ones in order to save one or two bearings, which may be the reason.

You'd better disassemble the motor to see if there are any signs of sweeping or water ingress. If none of these reasons are found, check your machine or measure the wire to see if the motor wire diameter is not enough, causing the wire to be overloaded. Check if the motor data is correct. Maintenance is also very important. The average is 20,000 to 30,000 hours! The bearing is broken! Regular maintenance and lubrication! I repaired an imported motor three years ago. It was only brought in last month. The motor coil is good, but the front shaft of the motor is broken. It's best to buy a regular motor.

3. The motor burns out only because of heat and insulation burns out. There are many factors that cause heat.

First, consider whether the load is too large, whether a small horse is pulling a big cart. It is best to equip a slightly more powerful motor. For example, a 1 kW motor should be equipped with a 1.5 kW motor.

The next thing is voltage. Is there a big voltage drop when so many motors are turned on at the same time? If the motor is working under voltage, it is easy to heat up and burn out.

Next, check if the three phases are balanced. If it is a three-phase motor, it is easy to heat up and burn the motor if the three phases are unbalanced. Next, check if your thermal relay protection device is intact. Consider replacing it with an electronic relay.

Motor burning is not only caused by overcurrent, but also by undervoltage and phase loss, so many aspects need to be considered.

If you start multiple motors as you said, I think the problem with the power supply will be more prominent.

Finally, consider visiting a maintenance point with more complete technical after-sales service to repair the motor.

Since there are more than 1,000 motors in the workshop, the motor burnout rate, or failure rate, is 1/1,000. If one motor burns out, then the motor has been used for more than three years. In addition, the workshop works 24 hours a day, so this situation is inevitable. It is normal and you don't need to worry too much.