120 volt DC Power supply.

[skotl]

@WorkshopChris , I think the 1.4 figure is what you multiply 240V AC RMS by to get the peak voltage. So mains is 240*1.4 = 336V peak.
I don't know how you could get more DC out than AC you put in without some clever electrickery...

You're contradicting yourself. Rectified DC voltage is 1.4 the AC RMS, so 240VAC in would be 336VDC out, no clever electrickery involved

Isn't rectified dc voltage higher than than the ac supply voltage.
You have me thinking now but i dont always trust my self this time of day due to pain killers.

Yes it is

 

[Hood]

The torque should be relatively constant no matter the voltage, well within reason.

 

[Crater Creator]

Just off the top of my head wont the ac voltage need to be around 85 /90v to get around 120v dc.

You're contradicting yourself. Rectified DC voltage is 1.4 the AC RMS, so 240VAC in would be 336VDC out, no clever electrickery involved








Yes it is

OK now I'm confused too....
Rectified unsmoothed DC voltage peaks are higher than input AC RMS, yes.... I agree
EDIT - yeah it doesn't get it down to 120. Right enough. Doh.

 

[skotl]

OK now I'm confused too....
Rectified unsmoothed DC voltage peaks are higher than input AC RMS, yes.... I agree

But you don't use it unsmoothed otherwise you'd have a rising/falling/rising DC voltage. Also, RMS AC is less than Vp or Vpp so smoothing the DC output gets you a value between RMS and Vp (roughly 1.4x Vrms);

http://www.allaboutcircuits.com/tools/rms-voltage-calculator/

Plug in 340V Vp to get 240V RMS

The diagram on that page neatly shows why you get more than the input VAC in VDC, where we have an input Vrms of 240V

 

[ukracer]

The torque should be relatively constant no matter the voltage, well within reason.

Nice...

 

[ukracer]

But you don't use it unsmoothed otherwise you'd have a rising/falling/rising DC voltage. Also, RMS AC is less than Vp or Vpp so smoothing the DC output gets you a value between RMS and Vp;

http://www.allaboutcircuits.com/tools/rms-voltage-calculator/

Plug in 340V Vp to get 204V RMS

Just please dont mention Pies...lol

 

[WorkshopChris]

Did someone say pie

 

[ukracer]

OK now I'm confused too....
.

Can you imagine what I am then. lol

 

[Johnnybravo]

Axis controls are the Uk agents for Kb electronics. I use one of their drives with a 3hp treadmill motor. Very good value for money at less than £100.

 

[WorkshopChris]

Can you imagine what I am then. lol

A quick google just found this pdf might be worth a read.
http://www.pdma.com/pdfs/Articles/DC_Motor_Analysis.pdf

Always worth a inspection and clean before powering up for the first time, as a minimum a good blow out with the airline.

 

[ukracer]

Axis controls are the Uk agents for Kb electronics. I use one of their drives with a 3hp treadmill motor. Very good value for money at less than £100.

I was thinking more like a tenner...lol

 

[Hood]

What is the amp rating of the motors? What RPM are you thinking you will want?

 

[Crater Creator]

But you don't use it unsmoothed otherwise you'd have a rising/falling/rising DC voltage. Also, RMS AC is less than Vp or Vpp so smoothing the DC output gets you a value between RMS and Vp (roughly 1.4x Vrms);

http://www.allaboutcircuits.com/tools/rms-voltage-calculator/

Plug in 340V Vp to get 240V RMS

The diagram on that page neatly shows why you get more than the input VAC in VDC, where we have an input Vrms of 240V

Yeah it's the fact that AC is talked about in RMS.
You can't get more DC out than the peak volts in, is what I was trying to say - badly.

 

[Pete.]

This will power any of those motors up to 180volts

http://r.ebay.com/V9ci7m

 

[Maker]

Something to test these with and see what I can make with them....View attachment 99647

Are they all 120 VDC? I've got a couple of treadmill motors just like those and I think one is 180 VDC.

I'd be interested in a cheap power supply too, preferably a homemade one so I could learn from it.

 

[WorkshopChris]

I'd be interested in a cheap power supply too, preferably a homemade one so I could learn from it.

Lots of info on the net if you want to get the bits together and build one. Just remember AC bites and lets go DC bites and keeps on biting.

 

[Hood]

Wonder if something like this would work, maybe worth trying although you would need a DC power supply capable of producing the current you require as well
http://www.ebay.co.uk/itm/60A-DC-Br...562778?hash=item25c2a7bd1a:g:IcYAAOSwIgNXveQa

 

[WorkshopChris]

Just something to think about a dc motor especially when the field winding's are connected in series with the armature can very rapidly accelerate almost to the point of self destruction if it does not have a load to drive. When connected to a fixed voltage supply.

 

[Pete.]

I think all those motors are permanent magnet.

There is another way to run a DC motor and that's with a CSR power regulator chip and bridge rectifier. I use this for the field supply on my lathe's DC motor. you'd have to figure your own protection via fuses or whatever.

http://www.farnell.com/datasheets/20572.pdf

 

[ukracer]

What is the amp rating of the motors? What RPM are you thinking you will want?

Not sure yet.. and until I get one running I am not sure what they will do. Oworked on the basis if they have enough power/torgue to move me...19 stone from a standstill they might be good welding positioner motors.

I want one to lift the workiing cross bar oon my new press if possible