Controlling the speed of AC fans can be a challenge – one method that can be used is a Triac controller. This is essentially an electronic switch that switches on the electro-magnets for only a proportion of each cycle. As the same amount of power is input, the unused power is lost, creating buzzing and humming at low speeds.
The second method is a stepped hybrid controller, which reduces the voltage with a transformer, reducing the magnetic strength and in turn reducing the speed of the motor. Transformers only offer a limited number of steps (usually 5 steps). The benefit is that as the frequency remains constant there is no humming or buzzing.
Benefits of AC fans:
- Highly economical
- Very efficient at 100% speed
- Quiet in operation (at high speeds)
Cost effective and reliable