Changing secondary voltage (Uncivilized way)

Nikon1975 · 15th February 2010, 11:28 AM

Question: I have a transformer 400-360-0-360-400 in a PSU I use for testing.
To switch between the 400 V and the 360 V, can I connect the rectifier to the 400 V taps and put a switch between the 360 and 400 V taps ?

When the switch is close it will work at 360V, when open at 400V.

Am i missing something ?

Thanks,

Davide

chrish · 15th February 2010, 11:59 AM

Why not use a DPDT (dual pole dual throw) switch and switch between the two 400 and 360 volt taps?

stevecole · 15th February 2010, 12:15 PM

You certainly CANNOT use your initial suggestion, as you will be shorting out 2 sections of your transformer secondary, which will fry it pretty quickly. The Double Pole Switch is a better idea, although still with some risk, as there will be rather a lot of voltage between adjacent poles of the switch. A safer option would be to terminate the secy's on suitably rated terminal blocks (one for each phase perhaps) and then select the ones you require with a link.

tomchr · 15th February 2010, 08:02 PM

If you can find a DPDT relay that can handle the voltage and current involved, I suggest switching between the two taps that way. I would not want 800 V present at some front panel switch. Note that the unused tap on the transformer secondary needs to be floating when not in use - hence the need for a DPDT (double pole, double throw) switch.

~Tom

Nikon1975 · 16th February 2010, 04:46 AM

OK, got the point, bad idea
:-(

D.

Richard Ellis · 18th February 2010, 04:39 AM

When working with switches there is another specification in addition to Voltage rating and current rating....that is:
"make before break"
AND
"break before make"

________________________________________________Ri ck....

15th February 2010, 11:28 AM	#1
Nikon1975 diyAudio Member Join Date: Nov 2009 Location: Tokyo	Changing secondary voltage (Uncivilized way) Question: I have a transformer 400-360-0-360-400 in a PSU I use for testing. To switch between the 400 V and the 360 V, can I connect the rectifier to the 400 V taps and put a switch between the 360 and 400 V taps ? When the switch is close it will work at 360V, when open at 400V. Am i missing something ? Thanks, Davide

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15th February 2010, 11:59 AM	#2
chrish diyAudio Member Join Date: Oct 2003 Location: Sydney	Why not use a DPDT (dual pole dual throw) switch and switch between the two 400 and 360 volt taps?

15th February 2010, 12:15 PM	#3
stevecole diyAudio Member Join Date: Apr 2008	You certainly CANNOT use your initial suggestion, as you will be shorting out 2 sections of your transformer secondary, which will fry it pretty quickly. The Double Pole Switch is a better idea, although still with some risk, as there will be rather a lot of voltage between adjacent poles of the switch. A safer option would be to terminate the secy's on suitably rated terminal blocks (one for each phase perhaps) and then select the ones you require with a link.

15th February 2010, 08:02 PM	#4
tomchr diyAudio Member Join Date: Feb 2009 Location: Greater Seattle Area	If you can find a DPDT relay that can handle the voltage and current involved, I suggest switching between the two taps that way. I would not want 800 V present at some front panel switch. Note that the unused tap on the transformer secondary needs to be floating when not in use - hence the need for a DPDT (double pole, double throw) switch. ~Tom

16th February 2010, 04:46 AM	#5
Nikon1975 diyAudio Member Join Date: Nov 2009 Location: Tokyo	OK, got the point, bad idea :-( D.

18th February 2010, 04:39 AM	#6
Richard Ellis diyAudio Member Join Date: Sep 2006 Location: Mar del Plata, a BIG seasonal getaway city, can see the Ocean from our residence.	When working with switches there is another specification in addition to Voltage rating and current rating....that is: "make before break" AND "break before make" ________________________________________________Ri ck....

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