145Views1Replies

Author Options:

How does lock protection work on HVAC fan Answered

The mpu detect the rpm and if no match it will stop the motor
how to differentiate if it is from a bad motor or a bad mpu circuitry  

10 Replies

user
steveastroukBest Answer (author)2011-10-10

Find out how its detecting speed - there is probably a sensor somewhere near the motor, or the edge of the fan.

Select as Best AnswerUndo Best Answer

user
steveastrouk (author)2011-10-11

Looks like it - else what ELSE can electronically set the speed - there isn't a relay anywhere else I noticed

Select as Best AnswerUndo Best Answer

user
steveastrouk (author)2011-10-11

WHICH speed ? If its fast only, change the SSR (SSR101)

Steve

Select as Best AnswerUndo Best Answer

user
steveastrouk (author)2011-10-11

Looking at it, they are making a single phase motor turn at different speeds just by switching the AC on and off.

Steve

Select as Best AnswerUndo Best Answer

user
steveastrouk (author)2011-10-11

Its possible to make your own three phase supply, if you throw enough electronics at it. Electronics are cheaper than motors with multiple windings now.

I'd need a copy of the full circuit to explain it in detail - I must say, this seems a very clever piece of equipment you have there !

Steve

Select as Best AnswerUndo Best Answer

user
steveastrouk (author)2011-10-10

Well the motor could be a three phase motor, and the system makes its own AC.

Select as Best AnswerUndo Best Answer

user
steveastrouk (author)2011-10-10

I think, given the history, I'd go with the new MPU board, especially since the pathway you think is broken would be pretty close to the way a lightning strike would find a weakspot.

New board, if the motor is spinning freely.

Steve

Select as Best AnswerUndo Best Answer

user
steveastrouk (author)2011-10-10

The right side is the wiring for the internal sensor. What I am trying to do for you is to see if the sensor is doing something - I suspect it should generate a little pulse every revolution, and you should be able to see that. The computer measures the time between pulses - too long and it sees the motor running too slow. Does it LOOK too slow ?

Steve

Select as Best AnswerUndo Best Answer

user
steveastrouk (author)2011-10-10

OK, the measurement is inside the motor. Have you got access to an oscilloscope by any chance ?

Failing that, put a DVM between pins 3 and 2, and observe the reading when the fan is "spinning".

Show me where the signal goes to the RIGHT of the picture./

Select as Best AnswerUndo Best Answer

user
steveastrouk (author)2011-10-10

So this IS a mains powered fan isn't it ?

Select as Best AnswerUndo Best Answer