The PWM switching frequency has to be much higher than what would affect the load (the device that uses the power), which is to say that the resultant waveform perceived by the load must be as smooth as possible.
eBay
380V Or 220V Economical VFD Variable Frequency Drive Converter Inverter 0.75/1.5/2.2/3.7/4/5.5/7.5/11 KW Motor Speed Controller
Aliexpress UK
Connector: 6 Pin.
eBay
4000W 0-220V AC SCR Electric Voltage Regulator Motor Speed Controller Dimmers
Aliexpress UK
Rated power: 800W. Applicable motor: 48V 350W-500W brush motor. Applicable motor: 48V350W-500W brush motor. 48V500W foreign trade thread head: 8 head. Suitable for electric tricycle, scooter, etc. Brake handle: the machine runs normally.
eBay
DC 12-60V 40A PWM Brush Motor Speed Controller CW CCW Reversible Switch
Aliexpress UK
It's engineered to provide users with an effortless way to regulate fan speed and ventilation, ensuring optimal performance and comfort. It also includes built in mounting holes, allowing for quick, secure installation onto any device.
eBay
4000W 220V AC SCR BTA41-600 Voltage Regulator Dimmer Electric Motor Speed Controller
Aliexpress UK
Current: 20A. Switching frequency: 25KHz. Durable in use. The positive and negative poles of the motor can be reversed.
eBay
Mini 5A 10A 90W PWM 12V DC Motor Speed Controller Module DC-DC 4.5V-35V Adjustable Regulator Control Governor Switch 24V
Aliexpress UK
Rated power: 350W. Automatic identification the 36V and 48V. Applicable model: electric bicycle, electric scooter. Casing material: Aluminium. Connect the power cord and note that the positive and negative poles should not be reversed.
eBay
380V Or 220V Economical VFD Variable Frequency Drive Converter Inverter 0.75/1.5/2.2/3.7/4/5.5/7.5/11 KW Motor Speed Controller
Aliexpress UK
The maximum output power : 400W(the power is 12V 10A =120W. 24V maximum power of 200W) PWM frequency is 21KHz ;. Suitable for the DC motor (or DC load) within 8A, Peak current 10A. TO CHANGE MOTOR DIRECTION, INTERCHANGE THE POSITIVE AND NEGATIVE WIRES OF MOTOR.
eBay
AC 10V-220V 4000W SCR Voltage Regulator Dimming LED Dimmer Motor Speed Controller Thermostat High-power Power Supply module
Aliexpress UK
Suitable for DC motors (or DC loads) up to 20A. The adjustable speed range is 0%-100%. Speed Range: 0-100%.
eBay
Mini 5A 10A 90W PWM 12V DC Motor Speed Controller Module DC-DC 4.5V-35V Adjustable Regulator Control Governor Switch 24V
Aliexpress UK