salvage transformer ideas

ultrachrome · 13th March 2005, 12:28 AM

I have this large EI transformer I'm hoping someone could suggest uses for.

115V 16 guage primary
30V 16 guage x 3 dual secondaries
70V 24 guage secondary

The laminations are 4.375" x 5.25" stacked 4" thick.

Weighs about 30lbs.

Any guesses about its VA rating?

Thanks.

Sch3mat1c · 13th March 2005, 02:30 PM

Awfully thick core.

3 x 30V @ 16AWG ~= 5A per = 450VA + 70V 24AWG = 1A = 70VA, total = 520VA.

115V @ 16AWG = 5A = 575VA, close enough.

Tim

ultrachrome · 13th March 2005, 06:43 PM

Thanks. Only problem is that it buzzes a bit.

planet10 · 13th March 2005, 07:19 PM

Quote:

Originally posted by Sch3mat1c
3 x 30V @ 16AWG ~= 5A per = 450VA + 70V 24AWG = 1A = 70VA, total = 520VA.

115V @ 16AWG = 5A = 575VA, close enough.

That comes real close to the 20VA/pound rule-of-thumb (ie 600VA)

dave

ultrachrome · 13th March 2005, 07:24 PM

I weighed it outside of the chassis and it's actually 25.5lbs. So I guess about 510VA?

Sch3mat1c · 13th March 2005, 07:53 PM

You can also calculate approximate VA capacity by core dimensions: if a wasteless cut, the center limb is 1 3/4" wide, and stack is 4" you say? That's 7 square inches, and according to a booklet I have, W = (5.6 * A)^2 = 1.5kVA... eh, maybe not! That book makes too many assumptions. Clearly it doesn't work with such an obesely stacked transformer.

Which reminds me, they used to do that for 25Hz transformers (i.e., use a given transformer design for whatever radio, and stack up the transformer and windings for the lower frequency models), but that it has the heavy wire suggests otherwise.

Tim

Sch3mat1c · 13th March 2005, 07:54 PM

Oh, and note you can easily draw 1 or 2kVA from it -- IF the insulation can tolerate the temperature rise and your circuit can tolerate the voltage droop.

Tim

ultrachrome · 13th March 2005, 07:56 PM

The transformer is from a 28VDC 18AMP continuous power supply that my employer was throwing out. I don't know what I'll do with it. I just wanted the chassis and heatsinks.

planet10 · 13th March 2005, 09:34 PM

Quote:

Originally posted by ultrachrome
28VDC 18AMP continuous power supply

Well that is 504VA by itself...

dave

megajocke · 15th March 2005, 09:20 PM

28VDC 18AMP?

If it is a linear supply that would men 18A from the filter bank. Most formulas suggest using a transformer with Iac = 1.8*Idc in bridge or Iac = 2*Idc if using full wave with center tap. If that formula was used in this one...

1.8*18=32.4
32.4*30=972
...

So something like 1000VA. Nice.

Even if it isn't that much, I would have used it in an amp, something like 4 channels of 80W/8ohms. It would probably have no problems doubling that into 4ohms either with that transformer...

13th March 2005, 12:28 AM	#1
ultrachrome diyAudio Member Join Date: Jan 2002 Location: Puget Sound	salvage transformer ideas I have this large EI transformer I'm hoping someone could suggest uses for. 115V 16 guage primary 30V 16 guage x 3 dual secondaries 70V 24 guage secondary The laminations are 4.375" x 5.25" stacked 4" thick. Weighs about 30lbs. Any guesses about its VA rating? Thanks.

13th March 2005, 02:30 PM	#2
Sch3mat1c diyAudio Member Join Date: Jan 2003 Location: Milwaukee, WI	Awfully thick core. 3 x 30V @ 16AWG ~= 5A per = 450VA + 70V 24AWG = 1A = 70VA, total = 520VA. 115V @ 16AWG = 5A = 575VA, close enough. Tim __________________ See my Electronics webpage -- the home of Vacuum Tube Drag Racing. The key to being a successful Audiophile: "I reject your reality and substitute my own!"

13th March 2005, 07:53 PM	#6
Sch3mat1c diyAudio Member Join Date: Jan 2003 Location: Milwaukee, WI	You can also calculate approximate VA capacity by core dimensions: if a wasteless cut, the center limb is 1 3/4" wide, and stack is 4" you say? That's 7 square inches, and according to a booklet I have, W = (5.6 * A)^2 = 1.5kVA... eh, maybe not! That book makes too many assumptions. Clearly it doesn't work with such an obesely stacked transformer. Which reminds me, they used to do that for 25Hz transformers (i.e., use a given transformer design for whatever radio, and stack up the transformer and windings for the lower frequency models), but that it has the heavy wire suggests otherwise. Tim __________________ See my Electronics webpage -- the home of Vacuum Tube Drag Racing. The key to being a successful Audiophile: "I reject your reality and substitute my own!"

13th March 2005, 07:54 PM	#7
Sch3mat1c diyAudio Member Join Date: Jan 2003 Location: Milwaukee, WI	Oh, and note you can easily draw 1 or 2kVA from it -- IF the insulation can tolerate the temperature rise and your circuit can tolerate the voltage droop. Tim __________________ See my Electronics webpage -- the home of Vacuum Tube Drag Racing. The key to being a successful Audiophile: "I reject your reality and substitute my own!"

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13th March 2005, 06:43 PM	#3
ultrachrome diyAudio Member Join Date: Jan 2002 Location: Puget Sound	Thanks. Only problem is that it buzzes a bit.

13th March 2005, 07:24 PM	#5
ultrachrome diyAudio Member Join Date: Jan 2002 Location: Puget Sound	I weighed it outside of the chassis and it's actually 25.5lbs. So I guess about 510VA?

13th March 2005, 07:56 PM	#8
ultrachrome diyAudio Member Join Date: Jan 2002 Location: Puget Sound	The transformer is from a 28VDC 18AMP continuous power supply that my employer was throwing out. I don't know what I'll do with it. I just wanted the chassis and heatsinks.

15th March 2005, 09:20 PM	#10
megajocke diyAudio Member Join Date: Jan 2003 Location: Solna	28VDC 18AMP? If it is a linear supply that would men 18A from the filter bank. Most formulas suggest using a transformer with Iac = 1.8Idc in bridge or Iac = 2Idc if using full wave with center tap. If that formula was used in this one... 1.818=32.4 32.430=972 ... So something like 1000VA. Nice. Even if it isn't that much, I would have used it in an amp, something like 4 channels of 80W/8ohms. It would probably have no problems doubling that into 4ohms either with that transformer...

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