How a DC motor changes speed
A DC motor changes speed simply by changing the armature voltage. Higher voltage → higher speed. That is why an adjustable speed DC motor is so easy to control compared with an AC motor, which needs a VFD.
Two control regions
| Region | What changes | Torque |
|---|---|---|
| Below base speed | Armature voltage 0 → rated | Constant torque |
| Above base speed | Field weakening | Constant power (torque drops) |
In practice, most drives run in the constant-torque region (armature control) and only a few need field weakening above base speed.
What your DC controller (drive) must match
| Spec | Why it matters |
|---|---|
| Armature voltage (160 / 400 / 440 V) | Must match your SCR or PWM drive output. |
| Field voltage | Field weakening and speed range. |
| Base & max speed (e.g. 750 / 1500 / 3000 rpm) | Sets the speed range you need. |
| Feedback (tach / encoder) | For precise speed regulation. |
Wangpai adjustable speed DC ranges
| Series | Application |
|---|---|
| Z4 series | Wide, smooth speed range and good regulation. |
| Z series | Heavy-duty variable-speed drive for cranes and mills. |
| ZZJ series | Mill auxiliary drive with frequent reversing. |
| YPT series | Asynchronous servo for variable-speed AC drives. |
Adjustable speed FAQ
What size do I need? Send load torque, speed range and duty. A common small drive is 5 kW; larger mill and crane drives reach hundreds of kW.
Do you supply the drive too? We supply the motor and tell you the correct armature and field voltages to match your controller (SCR or PWM).