there is a one question.I have created air heating system in my home. Based on it, I need have thermostats system with an arduinos, couple of thermostats and central unit with relays and triac regulation.
Question is : Is it possible to control an asynchronous motor with start capacitor with PWM on my arduino central unit ?
At this moment I have tested it, but in smaller rotation this motor create atypic sound and small knocking.
What I need for this type of motor (in test I have a MOC3041 and BT138 in standard circuit) ?
The word "asynchronous" is just another way of saying "induction" motor. The mention of a start capacitor implies single phase.
As MarkT says, induction motors normally need a VFD drive for speed control but if it is single single phase it would still not be suitable for speed control even from a VFD which is 3 phase. The big problem is that it has a starting winding and centrifugal switch which would come in at any speed substantially below rated and would soon burn out at least the starting winding.
It would be an interesting project to make a VFD for single phase which would also control the starting winding but it also sounds a bit masochistic.
Thanks guys for your minds .... based on it .. I need a fan, which can distribute 95°C, because a warm air is flowing thru two of 3fans ... I thought, that I mentioned it. I forgot, sorry.
This type from Dalap, will be used only for evaporative cooling and it is not really necessary to regulate rotation of him. But, I will be glad, if yes.
Well, I am still in testing phase and I have found this settings for Arduino Mega. Some of knocking/pulsing of fan can eliminate this idea from valerio_sperati : Arduino Playground - TimerPWMCheatsheet
If I have changed value of PWM pins (for me 7) in timer4 from standard 976Hz to 7812 Hz, the fan is little bit quiet and running without knocking.
What next you could write to my testings ? Especially phoxx, which comment was I have read carefully.
Those motors are "asynchronous" or "induction", not synchronous. If they were synchronous they would run at exactly 3000 rpm on 50hz supply and if you lowered the voltage they would still run at 3000 rpm until the voltage got too low then they would stall.
One thing I've seen with fans is that if the motor has a relatively high resistance rotor it can be used at lower than nameplate voltage to get lower speed. What saves them is that the load imposed by the fan falls off very rapidly as speed is reduced so the motor current stays down somewhere near full load. Of course the efficiency and power factor are very low when run this way. As for stability, with a high resistance rotor the speed/torque curve has a negative slope from near zero to rated speed so the fan load curve only crosses it once and the speed settles out to the value at the crossing point.
It makes for interesting arguments on a project if the rotor resistance is too low and the fan curve crosses it twice so the speed wanders back and back and forth between the two crossing points.
And if the motor isn't designed to run at low voltage then you can burn it out and start a fire
by running it at lower than nominal voltage. Induction motors can pull 5x the current or more
at stall as for full load. Big ones aren't supposed to be restarted more than a fixed
number of times per hour due to the rapid heating in the windings while they spin up...
Accepted.
My understanding of terminology would appear to be incorrect.
AIUI an induction motor is not synchronous as it depends on slip for operation.
I have read most documents about it .... mainly on the internet. What about this PDF at page 6 ???
But if you have a truth, than this Dalap motor is not usable for PWM control.
Is there a possibility to control speed of him ??
On the saler page is mentioned thyristor regulator.
What about combination of thyristor and F/V converter (LM331) ???? Could it be connected to PWM of arduino ?
Boardburner2:
The old fashioned clock motor was synchronous but a "reluctance" type. It had a strange looking rotor; a straight bar mounted crossways on the spindle and a ring around it, ie a circular ring with the bar on a diameter. It would then need only a bit of a shading turn on a stator pole to get started and finally the magnetic field would pull it around to line up with the bar. It was suitable only in very small sizes for a clock and could produce very little power.
A shaded pole motor is still an induction motor. The shading turn on half the motor pole works pretty much the same as a starting winding on a fractional HP single phase induction motor except that it is active all the time. Again it is suitable only for small sizes.
Bobo:
I quickly read through your reference and the first thing you must remember is that the author is trying to drum up business for his product so will tend to have a rosy view of it. And note that he is very specific in saying that it is purely for fan control. It probably works for a limited range of applications and outside that range will be a disappointment.