How to solve the problem of stepper motor overheating

How to solve the problem of stepper motor overheating

One of the most significant advantages of the stepper motor is that it can be controlled accurately in open loop system because the rotor position can be determined only by tracking the input step pulse, but an overheating problem occurs easily in stepper motor, so how to solve this problem if such condition occurs?

The harmfulness of the motor's heating phenomenon:

The effect of heat on the motor Although it does not generally affect the life of the motor, it is not necessary for most customers. However, severe fever can have some negative effects. If the thermal expansion coefficient of each part of the motor is different, the structural stress changes and the small change of the internal air gap will affect the dynamic response of the motor, and the high speed will easily lose the step. In some cases, excessive heating of the motor, such as medical equipment and high-precision test equipment, is not allowed.

Test results

Test results confirm that closed-loop step motors draw current only when needed, so they run cooler and with less power consumption than open-loop options. Consider actual tests that run both the open-loop and closed-loop variations to get the same motion profile:

Acceleration = 100 rev/sec2 and deceleration = 100 rev/sec2

Distance = 5 rev and speed = 10 rev/sec

Dwell time = 0.1 sec

Both carry set load inertia and rotor inertia and operate from a 48-Vdc power supply. Results in the graph below show that the average power consumption of an open-loop stepper system delivering such output uses 43.8 W.

Solutions

1. Reduce running current

Reduce the heat radiated from the motor, which is to reduce copper loss and iron loss. There are two ways to reduce copper loss: reduce the resistance and the current, which requires us to choose the motor with small rated current as much as possible. For 2-phase stepper motor, do not use parallel-motor unless serial-motor cannot use, but this often contradicts the requirements of torque and speed.

2. Reduce the idle (holding) current for the motor

For a selected motor, automatic half-flow control function and offline function of the driver should be fully utilized. The former will reduce the current automatically while the latter will cut off the current direction when the motor is in a static condition.

3. The current waveform is close to a sinewave

Besides, the current waveform is close to sine, so harmonic of subdividing stepper motor driver is less and heat from the motor is less. There are not many ways to reduce iron loss. Voltage grade is related to the loss. The high-voltage drive motor can improve the high-speed characteristic, but also causes the heat increasing.

4. Choose the appropriate drive voltage level

Proper drive motor voltage grade should be selected and those indexes, such as high-speed characteristic, smoothness, heat and noises, etc. should be also taken into account.