Re: [CAD_CAM_EDM_DRO] Stepper Power Supply. Question about Voltage

The voltage you have measured is the average (pulsing) dc voltage. When you
connect the capacitor then you will read the peak of the rectified ac supply
which is 1.41 times the rms value.

I would add a note of caution in playing with these supplies as they can be
vicious due to the stored charge in the capacitors which can provide a great
deal of energy (and fireworks) if shorted. The voltage does not decay very
quickly even when the ac supply is removed and a bleed resistor should be
fitted across the capacitor.

Regards Peter

----- Original Message -----
From: "kaynrc" <tom.kay@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Friday, January 18, 2002 6:39 PM
Subject: [CAD_CAM_EDM_DRO] Stepper Power Supply. Question about Voltage


> Hello
>
> I am just getting around to selecting some transformers to build
> sparate little power supplies for Dan Mauch's 5 amp boards, and each
> transformer is rated at 26 VAC, 5 amps. I plugged one in, and read it
> at 29.2 VAC, which is fine by me.
>
> Then I connected the bridge rectifier and got a surprise, which is a
> reading of 26 VDC. I had not yet hooked up the 10,000uf, 50 VDC
> capacitor. Because the VAC is supposed to be higher than the VAC (by
> a factor of 1.41) I expected the DC voltage to be higher, around 35
> to 39 VDC. Again, it might be important that I did not attach the big
> cap yet.
>
> So, what's going on? Will I notice a voltage increase when I add the
> capacitor? Why is my DC voltage so low just taken right off the
> rectifier, since it's only suppose to consume around 1.7V? Is the
> transformer perhaps too small to supply proper voltage? And last,
> these 521 oz-in motors that I got from Camtronics (and the circuit
> boards) can run up to 40VDC, so am I simply going to operating slower
> with somewhere around 25 to 30 VDC? Noticably slower?
>
> Thanks, Tom.
>
>
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