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Seeking advice on DC motor speed control

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velocette:
Hi Norman
Several posts with suggestions to reduce the voltage appear to be to drop the voltage of the Alternating Current from 220 volts.

Be very aware that this is a Direct Current Motor and will require a Rectifier of some description to make it work properly.

Using a Resistor to reduce the speed will reduce the power of the motor so at very low speed would not pull the skin of the proverbial rice pudding.

http://www.surpluscenter.com/Electrical/Motor-Speed-Controllers/90-180-VDC-SPEED-CONTROL-W-POT-11-2269.axd

is a link to an excellent AC to DC motor speed control. They can be tuned to the motor a bit tricky to set up but give good control over a wide speed range plus overload protection.

My workshop machines all all run with AC to DC speed controls. 

Eric



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John Rudd:
Velocette/Eric,
The resistor referred to is effectively in series with the speed control pot and not with the motor....

Thinking about this, the speed pot itself needs to be reduced in value, such that the original value is not changed....Ergo, if the speed of the motor were to be halved then the value of the pot needs to be halved but the total resistance of the lot and the resistor adds to the original value....

philf:

--- Quote from: John Rudd on January 11, 2014, 03:50:43 PM ---Thinking about this, the speed pot itself needs to be reduced in value, such that the original value is not changed....Ergo, if the speed of the motor were to be halved then the value of the pot needs to be halved but the total resistance of the lot and the resistor adds to the original value....

--- End quote ---

John,

I'm not sure about the need to keep the total value the same because if you look at the pictures only 2 connections to the pot are being used. (The wiper and one end are shorted together at the terminal block). Depending on how the circuit works you may only adjust the minimum voltage rather than the maximum. I would go for adding resistance for starters.

If you have the same controller are there any internal pots for setting max and min speeds?

Phil.

John Rudd:
Phil,
Not had the lid off... :zap:



but peering thru, I can't see anything adjustable... :scratch:

Might have look today if I get chance....SWMBO has some tasks for me....... :doh:

John Rudd:
I can report back success.....

I connected a motor to the output and with 240 mains connected the max output to the motor is circa 150v dc max.....
There is a small pot inside the unit that looks connected to the external pot, to provide some sort of min/max setting.
As this looks factory set (dab of paint/sealant or whatever) I was reluctant to twiddle....
Suffice to say the controller should power Norman's motor without risk of burning out....

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