Understanding the 4000 and 10000 watt ebay scr motor controller

Thread Starter

white aurora

Joined Sep 26, 2019
33
Hello all,
I have been curious about the what they call an scr motor controller/dimmer for sale on ebay.

https://www.ebay.ca/itm/12400661880...H9SjFXtDMRbLhDsh6vPQ|ampid:PL_CLK|clp:2334524

I have purchased one and reverse engineered the circuit. It makes some sense to me but not entirely. I am not sure that I understand why the entire circuit is sitting on the AC power rail with no reference to ground.

The circuit does not use scr's it uses a triac driven by a diac. Both the 4000 watt and 10000 watt controllers are identical in their layout except for the size of the components and the 10000 watt controller has a 24v cooling fan circuit added. I know that these circuits output AC and have to be put through a bridge to run a dc motor.

These are being used by many hobbyists to run machinery and they do work. They need to be run through an inductor and cap to remove the noise though.

Any thoughts/explanation on how these things work?
 

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LowQCab

Joined Nov 6, 2012
1,312
"" Any thoughts/explanation on how these things work? ""

Yeah, they are the cheapest Hack You can possibly devise to dim an Incandescent-Lamp.
I would be embarrassed to admit that I ever used one.
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LowQCab

Joined Nov 6, 2012
1,312
Noise from a chopped-up Sine-Wave,
and the associated RFI /EMI radiation and
un-necessarily generated Heat.

There are some applications were none of this stuff matters too much,
like an Incandescent-Light-Bulb-Dimmer,
but for Motor-Speed-Control it's a poor idea.

They are infamous for burning-up Transformers and Shaded-Pole-Motors.
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Thread Starter

white aurora

Joined Sep 26, 2019
33
Noise from a chopped-up Sine-Wave,
and the associated RFI /EMI radiation and
un-necessarily generated Heat.

There are some applications were none of this stuff matters too much,
like an Incandescent-Light-Bulb-Dimmer,
but for Motor-Speed-Control it's a poor idea.

They are infamous for burning-up Transformers and Shaded-Pole-Motors.
.
.
.
What if they are run through a bridge rectifier and then through a large inductor and cap? would that not smooth out the noise? Is the heat generated on the triac?
 

MaxHeadRoom

Joined Jul 18, 2013
23,907
What if they are run through a bridge rectifier and then through a large inductor and cap? would that not smooth out the noise? Is the heat generated on the triac?
That method of using a bridge after the Triac is used for Universal (AC/DC) motors, power tools etc.
NO cap.
 

LowQCab

Joined Nov 6, 2012
1,312
The Heat is generated everywhere.
The Triac will drop close to a Volt, times whatever Current You will be pulling, =Watts.

Running the Output through a Bridge, an expensive Choke,
and an expensive Capacitor, just to prevent burning up your Motor
because of a mis-application of a cheezy Circuit,
never works out to be much of a brilliant plan.

What is the Voltage and Locked-Rotor-Current of your DC-Motor ?
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.
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Thread Starter

white aurora

Joined Sep 26, 2019
33
The Heat is generated everywhere.
The Triac will drop close to a Volt, times whatever Current You will be pulling, =Watts.

Running the Output through a Bridge, an expensive Choke,
and an expensive Capacitor, just to prevent burning up your Motor
because of a mis-application of a cheezy Circuit,
never works out to be much of a brilliant plan.

What is the Voltage and Locked-Rotor-Current of your DC-Motor ?
.
.
.
I have a 90v 18amp(I think) treadmill motor
 

Thread Starter

white aurora

Joined Sep 26, 2019
33
The early ones used SCR bridge for control, see MC-60, the later versions used PWM, see MC2100.
Both schematics are on the site.
Have you removed the flywheel?

BTW, do you actually drive a white aurora?
The white aurora thing is that when I was a teenager I saw aurora (northern lights) that were white. The only time I have seen that.
 

Thread Starter

white aurora

Joined Sep 26, 2019
33
The white aurora thing is that when I was a teenager I saw aurora (northern lights) that were white. The only time I have seen that.
I have used an mc-60 (I only had one). I have several motors from Precor treadmills. They have custom made boards and were using scr's. They have large inductor cap combinations before the motor.
 

MaxHeadRoom

Joined Jul 18, 2013
23,907
The other options are the KB controllers that come up on ebay etc regularly.
The have from SCR bridge up to PWM styles also.
It is advisable to remove the flywheel though.


Quite a few Youtube Vid on the triac conversion
etc.
 
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