DC motor control

[Phill05]

Hope this is not the wrong place to ask.
I have a 1 1/2HP DC motor on a lathe that has a manual veriac controller I would like to change to electronic speed control has anyone done anything like this and could point me in the right direction where to obtain one please.

Phill

 

[Paul Hannaby]

Pretty much all the off the shelf electronic variable speed control systems will use a three phase motor so you would need to buy both motor and controller. However, if you know what you are doing, you could use a three phase inverter controller and add a three phase rectifier between that and your existing motor. Whether that would be much cheaper than buying a conversion kit with motor is debatable.

 

[CHJ]

I think you basically need a Triac control circuit.

See this section 6.2.1 Triac Control of DC Inductive Loads of this PDF. for basic principle but you will need the additional circuitry similar to that shown in 6.2.2 for your power control.

In effect replacing your Variable transformer with the Triac.

I don't know of any off the shelf 'boxes' that are available, I've only ever built them for much lower power requirements than 1-1/2HP.

 

[Phill05]

Many thanks for the information I don't really want to go down the road of changing the DC motor I just want to change the controller for cosmetic reasons as the box is +350 mm x 350 mm square and takes up some room, the motor and controller was fitted new 2000 - 2001 and has done only a small amount of work and has been in storage till now.
It would be nice if I could get one off the shelf

Phill

 

[Inspector]

In the early 80's I wanted a big bowl lathe and was looking for a motor when I saw a 2 hp dc motor at a local electrical and surplus place. They set me up with a 220vac single phase to 24vdc (I think) power supply. It had forward and reverse as well as variable speed in it and was about 6" x 10" x 4" or so in size. Afterwards I learned about the AC single phase to 3 phase units. They would have been the cheaper way to go and are likely still. So they are available but you have some hunting to do.

Pete