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180VDC Motor Start Up Circuit Design

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jwalton1

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Hello, Any help would be brilliant with this!
I need to create a method of taking a variable input from a 230V@10A dimmable socket in a theatre to convert it to a variable 180VDC to control a DC motor built into a treadmill the other side of the room with a constant run power requirement of 5 Amps. So far all I am using is a bridge rectifier and running the dimmer at a low level to convert it into DC but as you can probably imagine as soon as the motor is started the load on the motor causes the inrush to trip the 10A dimmers (the motor only has one run coil and no start).

Can anyone recommend a circuit that could be at the motor end of the setup using either capacitors or a resistor system that would require no human interaction apart from the dimming control to adjust the speed after start up.

Preferably cheaply!

Again, any help would be greatly appreciated.
 
(the motor only has one run coil and no start).
Yes, DC motors don't have start coils, that is just single phase induction motors.

The motor on your treadmill, what is the DC voltage required to run it at the maximum speed for your application?
While the motor is rated at 180 volts, maybe you only need (say) 100 volts.
In that case you could use a stepdown transformer to drive your rectifier.
If you had a 2:1 stepdown transformer, you would have only half the current in the dimmer compared withe the motor, eg 10 amps in the motor, but only 5 amps in the dimmer.

It also occurs to me that the dimmer may not like driving the inductive load of a motor or transformer, it could be that it is only happy with the resistive load of an incandecent lamp, in which case you are a bit stuck.

JimB
 
This is ALWAYS the problem with DC motors. They look like a short circuit when you bang them on line.
I have a 6 HP 440 volt DC motor which runs a pump. The controller uses a rectifier bridge with diodes in one half and thyristors in the other half. The timing arrangement uses a uni junction transistor to produce the drive pulses. Attached to the timing circuit of the unijunction is a transistor collector, the base circuit of which is controlled by a current sensing resistor in the motor leads.
The arrangement is very simple; one only needs to limit the start up current and when the motor is moving, the shunt transistor does nothing. I had a ASEA drive and cut it down to something simpler and added the current control. In your case you need to buy something I guess.
If you rectify a 230 volt AC waveform, it's average value will be 180 volt DC. Thats where the 180 volt comes from.
It sounds like you should probably buy something from say RS and adapt it if necessary.
 
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