What Is a Stepper Motor Drive? Types and Selection Criteria
A stepper motor drive is a power electronics device that converts pulse and direction signals from a PLC or motion card into regulated current for the motor windings.
A stepper motor drive is a power electronics device that converts the pulse and direction signals from a PLC, CNC control or motion card into a regulated current applied in sequence to the windings of a stepper motor. Each pulse turns the motor by one full step or microstep; the number of pulses sets the rotation and the pulse frequency the speed. A stepper drive only drives stepper motors; it does not replace a frequency inverter or a servo drive.
Types of stepper drives
- Pulse/direction input: Positions with a PLC's high-speed pulse output or a motion card. The GSTD models in the catalogue are of this type.
- Analogue speed reference: Runs the motor at a set speed from a reference such as 0–10 V; it suits speed control rather than positioning. The LGSD-0A10-8A is of this type and drives two motors together.
- DC and AC input: A DC input drive needs a DC power supply; an AC input drive can be fed from a stepper transformer. Some models accept both.
Models in the catalogue
| Model | Input signal | Supply | Output current |
|---|---|---|---|
| GMT GSTD2556 | Pulse/direction, up to 200 kHz | 24–60 V DC | 5.6 A |
| GMT GSTD2860 | Pulse/direction, up to 250 kHz | 18–80 V AC or 24–110 V DC | 8.4 A peak (6.0 A RMS) |
| GMT LGSD-0A10-8A | 0–10 V analogue, two motors | See the product page | 8 A (total of both motors) |
Check the supply and current of the GSTD2542 and GSTD22280 on the product page and in the data sheet. Supply ranges in the catalogue run from 18–40 V DC to 80–220 V AC; in the catalogue data, the motor lead type is given as 4 or 8 leads.
Selection criteria
- Output current: The adjustable current must cover the motor's phase current. Check whether the data sheet gives peak and RMS current separately; an 8-lead motor in parallel needs a higher current.
- Supply: An AC input drive is fed from a stepper transformer, a DC input drive from a DC power supply. A higher supply voltage maintains torque at high speed, but the drive's range cannot be exceeded.
- Input frequency and signal level: The maximum input frequency must cover speed times pulses per revolution: a 1.8° motor at 1/16 microstepping needs 3200 pulses per revolution, so 600 rpm (10 revolutions per second) needs 32 kHz. Check in the data sheet that the input level (5 V or 24 V) matches the PLC output.
- Microstepping: Finer microstepping smooths motion and reduces resonance, but needs a higher pulse frequency for the same speed.
- Protection: Optically isolated inputs, an alarm output and standstill current reduction make fault tracking easier and reduce heating; connect the alarm output to the PLC.
Common mistakes
- Setting the current above the phase current: The motor overheats; too low a setting reduces torque and causes missed steps.
- Connecting a 24 V PLC output directly to a 5 V input: The input can be damaged; use the series resistor recommended in the data sheet if needed.
- Running motor and pulse cables in the same duct: Noise on the pulse line causes extra or missing steps; use shielded cable.
Stepper drives in the catalogue
The Stepper Drives category has 5 active GMT products: GSTD2542, GSTD2556, GSTD2860, GSTD22280 and LGSD-0A10-8A. Suitable motors are in Stepper Motors; matching motor, drive and transformer is covered on the Stepper Motor Systems page.
Frequently asked questions
What does microstepping do?
The drive changes the winding currents in small increments to divide a full step into smaller steps; the motor runs more quietly and smoothly at low speed. Positioning accuracy remains limited by the motor's mechanical step accuracy.
How is the drive current set?
On most drives, as on the GSTD2860, current and microstep are set with DIP switches on the housing. Choose the value from the phase current on the motor label.
Do 4-lead and 8-lead motors work with the same drive?
Yes. An 8-lead motor is connected in series or parallel; because the connection changes the current the motor draws, set the drive current to the corresponding value in the motor data sheet.