Inverters vary supply frequency to control AC motor speed efficiently.
A VFD rectifies AC to DC then inverts via PWM to supply variable frequency and voltage (V/f control), allowing speed control and energy saving (pump power ∝ speed³). Vector control gives precise torque. Beware harmonics and bearing currents.
Slowing a fan by 20% cuts power by about half.
Variable frequency drives give smooth and efficient speed control of AC motors, which saves energy in pumps and fans.
Inverters vary supply frequency to control AC motor speed efficiently.
Variable frequency drives give smooth and efficient speed control of AC motors, which saves energy in pumps and fans.
Power in fans and pumps varies with the cube of speed, so a small speed reduction gives a large energy saving.
It changes the supply frequency and voltage together, keeping the flux roughly constant, so the motor speed follows the frequency.
Typical applications include reducing the speed of a fan to match the airflow need in a building, controlling a conveyor belt at variable speed and running a pump at lower speed to save energy on a variable demand system.
Study "Motor starting methods" first (topic 64 of 106 in Electrical Engineering). It covers the groundwork this topic builds on.
Constant V/f ratio. Regeneration. Sine filters for long cables.
Slowing a fan by 20% cuts power by about half.
The next topic is "Power generation methods", which builds directly on this one.
It is classed as Intermediate in Electrical Engineering (topic 65 of 106). It is an intermediate topic. Work through the beginner topics in Electrical Engineering first.
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