single phase motor control

Thread Starter

b.hughes

Joined Nov 16, 2016
4
hi guys, new here.
hopefully somebody can help me understand this.
i have an old single phase motor here, the control pcb is no longer functioning so i thought i would try to build a new one.
i have found different variations of control circuits with triac and diac combinations, but what has me a bit confused is that this older motor has 3 leads.
brown, black and blue.
the brown and black are connected to the mains and start run cap, but the blue lead was connected to a bridge rectifier.
what is the purpose of the DC signal here? im having a hard time finding any info.

i hope my question makes sense, thanks in advance.

ben
 

MaxHeadRoom

Joined Jul 18, 2013
28,617
Can you post a pic of the motor or give detail off the motor plate, if it has one.
Do you know what it came from?
It could have some kind of current sensor that switches the start cap, instead of a centrifugal sw.
Three leads usually indicate main and start winding connections and a common.
Max.
 

Thread Starter

b.hughes

Joined Nov 16, 2016
4
Hi Max,

this is an old discontinued motor from Ebm/papbst, it was in a magnetic stirring machine. (IKAMAG REO long discontinued)
i did find an old schematic, i dont if you can see it but ive highlighted the lead that has me a bit confused...
thanks alot for any ideas you can share..im pretty new to motor controllers but im looking forward to understanding them better..
cheers, ben
 

tcmtech

Joined Nov 4, 2013
2,867
Its using an overly complicated single SCR based phase angle control system to vary the speed.

If you connect your AC common line to Blue and the live line to the capacitor and black lines it should run normally.
 

MaxHeadRoom

Joined Jul 18, 2013
28,617
@b.hughes you may notice the AC side of the bridge is connected in series with the motor common line, the full wave DC derived and the SCR is on the DC side of the bridge.
Any varying conduction of the Triac will change the motor current.
Quite a neat way .
Max.
 
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Dodgydave

Joined Jun 22, 2012
11,284
Brown (br) capacitor to Neutral.
Blue (bl) to Live.
Black (sw) to Neutral.

Its a simple dimmer circuit with a bridge rectifier and Thyristor.
 
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