06-035-1 Ceiling Sweep Fan Control Via C-Bus

This application note explains how ceiling sweep fans can be controlled by C-Bus.

 

What could possibly happen if the capacitors are switched in parallel? Resonance with the fan inductance is possible, which can result in higher current and consequently higher speed, but the losses in a ceiling fan are high, and the "windage loss" of a fan increases approximately with the square of the rotating speed, so the peak voltages and currents will be limited.

I have used two relays with two capacitors to control Airflow and Mistral fans for 7 years in the tropics (room temperatures often exceed 30C )without mishap. Fans are used for at least 200 days of the year.

I realise that some fans theoretically could be stressed if operated in the resonant condition (with just the right series capacitor value) for extended periods at a very high ambient temperature, but it is not my experience.

Don