I am looking for a lab/bench symmetric power supply of up to +/- 100 volts DC at about 2 - 3 amps (so about 500 - 600 watts) and having a very difficult time finding it. The very rare ones I have seen are in excess of $1500. I need such a supply for testing purposes. I do not want to build one.
Does anyone know of one around a max of $500 ?
Thanks
Does anyone know of one around a max of $500 ?
Thanks
Could use 4 of these el cheapos
Amazon.com: Economical Bench Power Supply 0-50Volts, 0-3 Amps (CSI5003XE): Home Audio & Theater
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I may use a variac and a rectifier and caps but not sure how to make a symmetric output without a center tap (variacs dont have center taps).The Variacs I know do not have galvanic isolation such that if you just add a rectifier and caps you will be testing electronics directly connected to the power grid! I see rayma's suggestion as a very realistic proposal for what you really need if you want to stay alive.
You may combine a Variac with a galvanic isolating transformer with a double center-tapped secondary winding. There will be no feedback stabilization and it will be rather bulky but at least you may have no safety hazard.
You may combine a Variac with a galvanic isolating transformer with a double center-tapped secondary winding. There will be no feedback stabilization and it will be rather bulky but at least you may have no safety hazard.
Yes, that is what I was thinking anyway. It will be very bulky & heavy but it would work.
I do already have a 1000VA 120 V -> 2 x 50 volt toroid. That would give me up to about 2 x 70 volts rectified dc. I have already 30 x 10,000uF 200 volt electrolytics I just need a 35 - 50 amp rectifier and this would be a fantastic dual power supply with about 2-3% regulation. Which is good enuf for power amp testing.
I do already have a 1000VA 120 V -> 2 x 50 volt toroid. That would give me up to about 2 x 70 volts rectified dc. I have already 30 x 10,000uF 200 volt electrolytics I just need a 35 - 50 amp rectifier and this would be a fantastic dual power supply with about 2-3% regulation. Which is good enuf for power amp testing.
You did not tell you already had a suitable transformer and caps with that capacity. Then do:
What size VARIAC variable transformer do I need for my hot wire applicaiton? | ISE Frequently Asked Questions
followed by (option (C)):
Different topologies of symmetrical rectifier circuits analyzed in this... | Download Scientific Diagram
Split the 30x10,000uF capacitors in two groups of 15 to replace each of the capacitors shown. Keep the bleeding resistors - 2x70V with 2x150000uF storage is not without danger! When turned down or switched OFF the bleeding resistors will remove the charge (in some time).
I am not sure 2-3% is what you get depending on how you measure. Dynamically, you will have an enormous stabilization from the 2x150000uF. Statically, the drop with increased loading may be more than 2-3% but you can compensate with your Variac.
I suggest you turn ON such a supply by starting the Variac at 0V and then turn up.
Good luck and be careful with the voltage!
What size VARIAC variable transformer do I need for my hot wire applicaiton? | ISE Frequently Asked Questions
followed by (option (C)):
Different topologies of symmetrical rectifier circuits analyzed in this... | Download Scientific Diagram
Split the 30x10,000uF capacitors in two groups of 15 to replace each of the capacitors shown. Keep the bleeding resistors - 2x70V with 2x150000uF storage is not without danger! When turned down or switched OFF the bleeding resistors will remove the charge (in some time).
I am not sure 2-3% is what you get depending on how you measure. Dynamically, you will have an enormous stabilization from the 2x150000uF. Statically, the drop with increased loading may be more than 2-3% but you can compensate with your Variac.
I suggest you turn ON such a supply by starting the Variac at 0V and then turn up.
Good luck and be careful with the voltage!
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Personally I'd just wire 10 of these in series: Turnigy nano-tech 460mah 3S 25~40C Lipo Pack
You'd also have to buy a charger, although they're cheap. Or you can use the batteries inline with something like this: New 400W LED Switching Power Supply 85-265VAC input power supply 100VDC Output | eBay
If you go this route, remember to add an inline fuse.
EDIT: I see you're looking for +-100vdc. That'll start to eat some space.
You'd also have to buy a charger, although they're cheap. Or you can use the batteries inline with something like this: New 400W LED Switching Power Supply 85-265VAC input power supply 100VDC Output | eBay
If you go this route, remember to add an inline fuse.
EDIT: I see you're looking for +-100vdc. That'll start to eat some space.
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@rayma, here are some basic but maybe important questions as I've seen it come up over and over again here an other places.
1. Why the need for the isolation transformer?
2. Would fuses in series with the main line/primary work?
3. GFI Outlet/inlet?
4. Are these simple test to identify/measure if a transformer or power supply is isolated?
It seems this is often overlooked or not discussed much in ELE programs.
Cheers,
1. Why the need for the isolation transformer?
2. Would fuses in series with the main line/primary work?
3. GFI Outlet/inlet?
4. Are these simple test to identify/measure if a transformer or power supply is isolated?
It seems this is often overlooked or not discussed much in ELE programs.
Cheers,
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continued from my prior post...
Because the system wouldn't let me edit the prior post I'll include it here:
Mentioned in passant:
Paynter & Boydell, Electronics Technology Fundamentals, 2nd ed. (pp 296, 301), mentions isolation transformer are 1:1. Floyd's electronic devices, 9th ed., (pp 725-729) doesn't mention them either, however the text does mention Isolation Amplifier in the
"Special-Purpose" Op-Amp Circuits section. There was no corresponding reference to Steve Martin's movie "The Jerk" regarding the discovery of his "special purpose" either.
Grob's Basic Electronics, 11e, (p574) has no reference to "isolation transformer" but does mention "Isolation of the Secondary" in the Autotransformer section. Perozzo's, The Complete Guide to Electronic's Troubleshooting, (1994) p57 devotes a paragraph to using an isolation transformer in the Safety and Cautionary Notes section. Nothing was found on p94 as that was also an indexed page. Anyway, at least that is a perusal of some texts easily accessed on my shelf.
Cheers,
Because the system wouldn't let me edit the prior post I'll include it here:
Mentioned in passant:
Paynter & Boydell, Electronics Technology Fundamentals, 2nd ed. (pp 296, 301), mentions isolation transformer are 1:1. Floyd's electronic devices, 9th ed., (pp 725-729) doesn't mention them either, however the text does mention Isolation Amplifier in the
"Special-Purpose" Op-Amp Circuits section. There was no corresponding reference to Steve Martin's movie "The Jerk" regarding the discovery of his "special purpose" either.
Grob's Basic Electronics, 11e, (p574) has no reference to "isolation transformer" but does mention "Isolation of the Secondary" in the Autotransformer section. Perozzo's, The Complete Guide to Electronic's Troubleshooting, (1994) p57 devotes a paragraph to using an isolation transformer in the Safety and Cautionary Notes section. Nothing was found on p94 as that was also an indexed page. Anyway, at least that is a perusal of some texts easily accessed on my shelf.
Cheers,
Why would a variable transformer designed for consumer use and sold legally via Amazon, Parts Express, etc not be isolated, and hence violate electrical code? The wiper is on the isolated secondary winding and the primary winding is separate and double insulated from the secondary - like most toroidal trafos we use for PSU’s.
I think the assumption that they are not double insulated and unsafe is not true for commercially available consumer grade units.
Having said that, you could instead try these 10amp DC-DC converters with max 50v output. Feed each with a 5amp 24v SMPS LED lighting brick. Take two of these units and tie in series +ve of one to -ve of the other and make the common 0v GND. The DC-DC converters are step/up and down and have adjustable voltage output. You can adjust for almost any voltage you desire and even can set up asymmetric rails (one higher than the other). What’s important here is that the SMPS have an output that is not referenced to mains earth ground. The SMPS cost $15ea and DC-DC converters are $7ea. For $44 you have your self a system that can power up to about 2.5amps at +/-35v. I have used it on a Class A amp (Pass M2) and it works quite well. Much quieter than a linear toroidal trafo and rectifier and typical massive CRC rail caps.
These are step up only but you can find ones that go up and down. Mount them to a heatsink like baseplate of case if drawing high current.
250W Boost Converter DC/DC 8.5 48V to 12 50V Output Step up Module Mobile Power Supply Max 10A-in Inverters & Converters from Home Improvement on Aliexpress.com | Alibaba Group
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You may be right. I know that type of non-isolated transformers under a different name from the past. I looked for "Variac" transformers on the Internet and when I found a diagram/drawing it matched the non-insulated design I knew. This is the basis for my assumption.
It seems the OP has a Variac (isolated or not), a 1KVA transformer (isolated) and some solid capacitors. With these elements a symmetrical power supply can be made. To get the symmetrical output voltages the transformer will need to be used (with these elements). If there is already isolation in the Variac it will be double.
I believe the OP understands his options and that a design with his present elements will not be the most elegant (rather bulky). But, the construction can be made quickly and may solve the task.
It seems the OP has a Variac (isolated or not), a 1KVA transformer (isolated) and some solid capacitors. With these elements a symmetrical power supply can be made. To get the symmetrical output voltages the transformer will need to be used (with these elements). If there is already isolation in the Variac it will be double.
I believe the OP understands his options and that a design with his present elements will not be the most elegant (rather bulky). But, the construction can be made quickly and may solve the task.
well maybe I am not up to date, yet I have never seen such an single transformer isolated variac. Usually there are (where?) two transformers in an isolated unit.
Non-isolated variacs should be legal if they are purposed for feeding mains powered devices.
My mistake then - I guess since they have mains outlets on them, they are compliant because only mains capable devices are to be connected. It would seem that a nice product would be to have one with a variable secondary winding.
This was good reading
Transformers - The Variac
Rod Elliot says isolated secondary Variacs do exist - they are just not as common.
This was good reading
Transformers - The Variac
Rod Elliot says isolated secondary Variacs do exist - they are just not as common.
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1. Why the need for the isolation transformer?
Yes, safety and code.
2. Would fuses in series with the main line/primary work?
Yes, very necessary also.
3. GFI Outlet/inlet?
No.
4. Are these simple test to identify/measure if a transformer or power supply is isolated?
Galvanic isolation from the AC line, so a separate transformer winding.
Yes, safety and code.
2. Would fuses in series with the main line/primary work?
Yes, very necessary also.
3. GFI Outlet/inlet?
No.
4. Are these simple test to identify/measure if a transformer or power supply is isolated?
Galvanic isolation from the AC line, so a separate transformer winding.
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Yes, a Variac is a variable autotransformer.
VARIAC® is the registered trademark of ISE, Inc.
Variac Variable Transformer Selector
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