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Just wondering how does speed control on a washing machine work?
I usually just replace the card but now I am curious as to how it controls the speed of the motor.
Given that the formula for controlling the speed of the motor is “RPM = 120 x frequency of supply / number of poles “I just assumed that you changed the number of poles in the motor? Or is it easier to change the frequency?
Re: Motor speed control
the formula you quote is for induction motors. carbon brush motors (series field) in theory are load dependant and have no top end speed if run unloaded with a un interupted supply. electronic speed control chops the 50Hz sine wave thus giving a burst of supply every 100th’s of a second. by altering the length or this burst of supply more of the sine wave cycle is allowed to be completed and and thus the speed altered. the tacho generates a small voltage fed back to the module as a referance
well something like this!!!!!!!!!!!!!
wilf
Re: Motor speed control
Ok wilf thanks for that.
So if I understand you correctly it would be something like in this sketch
I have drawn a motor plug. I just assumed that the centre tap to the field windings gave you half speed. So why would you need a centre tap if the speed is controlled by the amount of sine wave allowed through?
Or am I just totally off track here?
Re: Motor speed control
Centre tap effectively turns off half of the field coil and gives up to 40{e5d1b7155a01ef1f3b9c9968eaba33524ee81600d00d4be2b4d93ac2e58cec2d} higher revs on full volts. Big reduction in torque though.
Chris.
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