# 250V DC power supply



## Forge Boyz (Nov 7, 2014)

Anyone know a source for a 250V DC power supply? I have a customer looking for one to power a magnet. He says it is a 10 amp load. That's all the info I have. I haven't seen it and don't know the manufacturer.

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## CoolWill (Jan 5, 2019)

Forge Boyz said:


> Anyone know a source for a 250V DC power supply? I have a customer looking for one to power a magnet. He says it is a 10 amp load. That's all the info I have. I haven't seen it and don't know the manufacturer.
> 
> Sent from my XT1650 using Tapatalk


How about a bridge rectifier and filter capacitor?


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## Forge Boyz (Nov 7, 2014)

CoolWill said:


> How about a bridge rectifier and filter capacitor?


He told me it needs 250v and that a rectifier won't work because it's only 230-240v. It's a magnet for on a crane and they always have a power supply mounted on the machine. 

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## MikeFL (Apr 16, 2016)

I had something in mind until you said it's mounted on a crane. 
Is this crane outdoors?
What are the ambient conditions?

Your supply is 240VAC and you need 250VDC 10A output?

You may want to check with the manufacturer/supplier/ dealer of the crane and of the magnet. Ask them how they do it.


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## joe-nwt (Mar 28, 2019)

Use a step-up to increase your input voltage to the rectifier.


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## Forge Boyz (Nov 7, 2014)

Ok. I talked to the guy again and he said he just wants to be able to test the magnet. So I would be looking for a cheap way to do it. Then he remembered that he just might have a power supply on another machine and is going to check that out. Thanks for your input. If it doesn't work for him with what he has I might be back asking how to do a rectifier as I haven't ever worked with them.

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## just the cowboy (Sep 4, 2013)

*We did this*

Way back when.........
We took a Variack and ran it to a step up transformer then to the full wave bridge. Set proper voltage then hooked up test weight. We could then turn down voltage till weight dropped off to prove % voltage drop was safe.

Cowboy


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## oliquir (Jan 13, 2011)

just use 208v 3ph + a 3 phase rectifier, it will gives you about 243vdc with a lot less ripple than single phase rectifier, no need for capacitor


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## Forge Boyz (Nov 7, 2014)

oliquir said:


> just use 208v 3ph + a 3 phase rectifier, it will gives you about 243vdc with a lot less ripple than single phase rectifier, no need for capacitor


No 208 on sight. They do have 480v

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## CoolWill (Jan 5, 2019)

Forge Boyz said:


> He told me it needs 250v and that a rectifier won't work because it's only 230-240v. It's a magnet for on a crane and they always have a power supply mounted on the machine.
> 
> Sent from my XT1650 using Tapatalk


240 volts AC rectifies into about 338 volts DC. Then you can PWM it to what he needs.


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## Forge Boyz (Nov 7, 2014)

This is good. I'm learning things. I've never worked with DC much before.

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## JRaef (Mar 23, 2009)

Buy a used 2 quadrant DC drive with a 480V input, lots of people are pulling these out to replace them with AC drives and motors, so the old DC drives end up surplus sites for dirt cheap. 



240V input only gets you to 180VDC output..


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## splatz (May 23, 2015)

CoolWill said:


> 240 volts AC rectifies into about 338 volts DC. Then you can PWM it to what he needs.


 Is that or vice versa? 



If it's reversed, am trying to think if there's something you can do with transformer taps to make 338VAC...


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## CoolWill (Jan 5, 2019)

splatz said:


> Is that or vice versa?
> 
> 
> 
> If it's reversed, am trying to think if there's something you can do with transformer taps to make 338VAC...


VAC x sqrt2 = peak DC, which without the capacitor averages to 0.637 x peak. With the capacitor, the voltage is pretty close to the peak.


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## oliquir (Jan 13, 2011)

CoolWill said:


> 240 volts AC rectifies into about 338 volts DC. Then you can PWM it to what he needs.


thats only when using capacitors, if no capacitor you will get 240vdc minus losses in rectifer


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## CoolWill (Jan 5, 2019)

oliquir said:


> thats only when using capacitors, if no capacitor you will get 240vdc minus losses in rectifer


You get roughly 215 volts DC average, after rectifier losses with no capacitor.


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