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LAN_403

HazzWold 1993

Wed May 26 2010, 01:55PM

Registered Member #2563 Joined: Mon Dec 21 2009, 10:17AM
Location: Australia
Posts: 280

Hey this may be a stupid question but how can i go about rectifying 240VAC 50Hz mains. i have 385VDC capacitors that need charging to some degree.
i have a 3 phase bridge rectifier. could i use a single phase from that? or... what.

dmg

Wed May 26 2010, 02:10PM

Registered Member #2628 Joined: Fri Jan 15 2010, 12:23AM
Location:
Posts: 627

well, a simple bridge rectifier that you can get for less then a dollar will do, Im not sure about the 3 phase one though (six pulse I assume)

you can still rectify it on the three phase by using the first 2 connections, but Im not sure what effects will happen from that extra diode pair.

lpfthings

Wed May 26 2010, 02:18PM

Registered Member #1361 Joined: Thu Feb 28 2008, 10:57AM
Location: Cairns, Australia
Posts: 305

Just find a "bridge rectifier". Because of your voltage and mains frequency, I assume you are in Australia or Europe, in which case, one of these should do it:

Also, if you are using mains to charge a capacitor directly, without a transformer, you will need a NTC thermistor to prevent the initial surge current from tripping your breakers and blowing up your rectifier and capacitor.

IamSmooth

Wed May 26 2010, 02:20PM

Registered Member #190 Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567

I used two 450vdc capacitors in series for a total of 900vdc. I bought a bridge rectifier of suitable amperage and mounted it to a heat sink. My rectifier is set up as a doubler using 240vac and easily handles 40-50a

Bjørn

Wed May 26 2010, 02:35PM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

Connect two of the inputs, if the third looks lonely you can connect it to one of the other two. You can use a 240 V lightbulb in series to limit the inrush current so you don't blow the rectifier or the mains fuse. Be really careful and don't leave any exposed connections that curious people can touch.

HazzWold 1993

Wed May 26 2010, 11:23PM

Registered Member #2563 Joined: Mon Dec 21 2009, 10:17AM
Location: Australia
Posts: 280

lpfthings wrote ...

Just find a "bridge rectifier". Because of your voltage and mains frequency, I assume you are in Australia or Europe, in which case, one of these should do it:

With the thermistor do i have it in parallel to the mains or in series with the hot line? also should it be rated above the rated ratings of my house power. our plugs are all 15 amp lines and that one you gave a link to is rated only to 10 amps.
Also. would a 400 volt 35 amp bridge rectifier be okay?

HazzWold 1993

Wed May 26 2010, 11:29PM

Registered Member #2563 Joined: Mon Dec 21 2009, 10:17AM
Location: Australia
Posts: 280

Actually to just get the thermistor out of the picture.
What would be a suitable transformer to have in there. could i run a MOT into another MOT run in reverse? it would probably leave me with very low current though.....
???help

dmg

Wed May 26 2010, 11:55PM

Registered Member #2628 Joined: Fri Jan 15 2010, 12:23AM
Location:
Posts: 627

running two mots in that configuration will probably leave you under the 10A output, since ive used that to ballast MOTs.
(never actually messured the current) but I will tell you it most definatly pulled under 10A since the fuse did not burn out.
if you need more current, then you may need to remove the shunts from those 2 transformers.

by running these 2 mots in reverse, you are reffering to

input power - primary - secondary to secondary - primary - output?

HazzWold 1993

Wed May 26 2010, 11:59PM

Registered Member #2563 Joined: Mon Dec 21 2009, 10:17AM
Location: Australia
Posts: 280

gatedbreakdown wrote ...

running two mots in that configuration will probably leave you under the 10A output, since ive used that to ballast MOTs.
(never actually messured the current) but I will tell you it most definatly pulled under 10A since the fuse did not burn out.
if you need more current, then you may need to remove the shunts from those 2 transformers.

by running these 2 mots in reverse, you are reffering to

input power - primary - secondary to secondary - primary - output?

Yes thats the configuration im reffering too.
Would it be suitable?

dmg

Thu May 27 2010, 12:03AM

Registered Member #2628 Joined: Fri Jan 15 2010, 12:23AM
Location:
Posts: 627

I belive it will, there was a small amount of inrush upon startup, but the outer mot showed no noticable inrush current , or atleast to the point where it should be off any concern when I ran a MOT off this setup, and both MOTs were identical units.
also, when I run this, I used MOTs with shunts in them (unmodified whatsoever)

It will probably be a good idea to messure the output current from your setup

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