Need Help!- POWER SUPPLY IDEA!

[albertsteptoe]

Hello

Has anyone thought of using UK Building Site 110v transformers to power there stepper motors?

If you take a standard 230v to 110v AC Site Transformer and convert it to full wave DC rectification, you get 155.5v DC at a standard current of approx 16A.

The 155.5v DC voltage is high i agree but with a design including a current chopper circuit, i really cannot see any problem?

Take for example a motor, its 3A per phase with a coil inductance of 3.2mH.
Now running the motor at say 4Khz would induce an internal resistance of nearly 80 ohms due to the inductance at that frequency.

Now divide the 155.5v by 80 ohms = 1.94 amps, not 3A but not bad at 4Khz.
Hey presto, a cheap power supply for around £40 quid!

Would love to hear your thoughts on this.

Thanks
Albert Steptoe

[NC Cams]

why not buy 2, run them in parallel pre rectification, and get dwoble the current. Guys do it all the time with ATX P/S's. Did the same things with train transformers when I was a kid.

[albertsteptoe]

Hi NC Cams

Well yes but i was thinking more about the voltage.
It will be 155.5v DC with an ideal 16A.

Some designers on here use 75v supplies which in reality is still not enough when running steppers at high speed..
Having the 155.5v DC means there's plenty of headroom at low cost!

Just wondering if anyone else has used UK Building Site 230v to 110v transformers?

They are cheap to buy, robust and easy to convert.
Cannot think why its not been mentioned before?

Trying to get very high currents of around 16A with voltages around 100v is expensive, even on ebay.

Cheers!
AlbertSteptoe

[Al_The_Man]

For the most part, a transformer is a transformer, just because it is intended to be used as a particular function does not preclude it from other uses, as long as the ratings are OK.
The only thing you may have to check is because it is intended for building site use is if the secondary is isolated from ground or referenced to ground.
I have been away from the UK for some years so I am a bit out of touch on the regs now.
If it is isolated, this gives you the option of total isolation, grounded AC (neutral).or grounded DC, but not both!
If my memory serves me right, the sec. was isolated.
Al.