General-purpose stepper motor drivers are all constant current choppers. So, in practical applications, what impact do the driver's drive voltage and set current have on the stepper motor's performance?
In general: voltage affects speed, and current affects torque.
The torque-frequency characteristics of a stepper motor are measured under a specific current and voltage. When the current and voltage change, its torque-frequency characteristics will also change accordingly.
For example, for the 85 motor, which is suitable for voltage fluctuations, drivers from 24V to 220V can be used. The FY86EC502A has a torque of 6 N·m, which is the static torque under DC 80V and an average current of 5A. At 300 rpm, the torque is about 5.2 N·m. If we increase the current to 6A, the static torque increases to 6.3 N·m, and the torque at 300 rpm increases to 5.4 N·m. If we reduce the voltage to DC 24V while keeping the current at 5A, the static torque is only 5.7 N·m, and the torque at 300 rpm is only 4.3 N·m.
Relatively speaking, under the same current, voltage has a greater impact on the speed of a stepper motor. For example, a motor can idle at a maximum speed of 2100 RPM with DC 24V, but can idle at a maximum speed of 3200 RPM with DC 48V. Under the same voltage, adjusting the current has a more significant impact on the torque of the stepper motor.
It is incorrect to say that current affects torque and voltage affects speed. Changes in both current and voltage will alter the torque-frequency characteristics of a stepper motor. Changing the voltage will also change the torque of the stepper motor, and changing the current will also change the high-speed performance of the stepper motor.
It is worth noting that:
First, increasing the voltage or current will increase the stepper motor's heat generation. Overheating of the stepper motor can cause thermal demagnetization, so it is best to choose a motor specification with a certain margin of safety.
Secondly, when the motor torque is sufficient, we try to set the current to a level slightly lower than the rated current. This can extend the service life of the stepper motor and driver.
Third, for a driver rated at 80V, we should try to use it at around 70V. The rated voltage is AC18-80V, but both residential and industrial electricity have voltage fluctuations. The peak current and voltage at the moment of power-on and power-off are very high, so leaving some margin will greatly reduce the return rate. Some smaller brands of stepper motor drivers may specify a voltage range of C24-0V for drivers using 100V capacitors. If users actually supply power at 80V, it is somewhat dangerous.
