How do you change the frequency of a motor?
VFDs can be used to control AC motor speeds by changing the motor’s frequency without sacrificing the output power of the motor. This is done by turning the speed pot (explained in section three) of an AC motor drive.
What is frequency control method?
Variable Frequency Control is a method that is used to control the speed of an induction motor. The synchronous speed and therefore, the speed of the motor can be controlled by varying the supply frequency.
What happens if 50Hz motor is driven at 60Hz?
When a 50Hz single phase motor is brought to 60Hz the start function can be upset because the motor reaches the centrifugal switch speed 20% earlier than normal. When it does, the starting torque of the motor is suddenly reduced. It could fail to speed up further and never reach normal running speed.
How does frequency affect current in a motor?
4 Answers. An AC motor stator is an inductance. In an inductance, the lower the frequency, the lower its impedance. So having constant voltage over it, the current will rise if the frequency gets lower.
How does frequency affect horsepower?
You can use the HP and torque equations to verify this relationship. When a VFD increases frequency above 60 hertz, HP and torque do a complete flip flop. HP remains at 100 percent, and torque decreases as frequency increases. The torque reduction occurs because motor impedance increases with increasing frequency.
What happens when frequency changes?
From these equations you may realize that as the frequency increases, the wavelength gets shorter. As the frequency decreases, the wavelength gets longer.
Can you control the speed of an AC motor?
The most common way of controlling AC motor speed is changing the motor’s frequency. … The AC frequency can be adjusted using a six-step inverter, vector flux or pulse-width-modulation. A six-step inverter or variable voltage inverter rectifies the AC power to DC power, and then switches to imitate a sine wave.