Use an AC relay with DC?

Alright so I want to make something to magnetize screwdrivers with a pulse, basically taking the 400 volts dc from a PSU's capacitors. I have a few relays from some UPSes, however they are all rated for AC except one which also does DC, but significantly less than the AC rating.

The first relay I have s an OEG 0Z-SS-112L
It seems to be triggered by 12v DC, and can take 120vac at 20 amps, 240vac at 16 amps, but on the other side of the relay there is the circuit marking for a switch, with 16a/240v~ and 16a/30v~ on it.

My next relay is an OEG ORWH-SS-112D1F
It's marked for 15a 125vac and 10a 277vac

My next relay is an omron G2r010E, and is markes for 12 amps, either 240vac or 16vdc

My last relay option is a schrack RP 710024, apparently switching with 24vdc and rated for 16a, 250vac

So, can I use any of these with high voltage dc? What is the difference between a DC and AC relay?

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framistan4 years ago
There is ONE THING you are not taking into consideration. That is CORE SATURATION. If you magnetize something metal, such as any iron core or metal rod, the metal will reach a certain amount of magnetic strength and then will NOT get stronger magnetically if you ADD MORE VOLTAGE. That is because all the atoms are aligned and MORE VOLTAGE will not make any more of them align (electron spin aligned). So maybe it is not necessary to use 400 volts? You may want to read articles about people who make "rail-guns" or coil-guns. They deal with pulses and magnetizing things. This is one of those subjects that seem to be simple until you get more involved with it.
XOIIO (author)  framistan4 years ago
Yeah, you're probably right, It's just going to be tricky to get high ams that I can use, I only have DC capacitors available, although I do have a bridge rectifier,

I've kinda toyed with the idea of using Ac to charge the DC cap since it would only see half the wave but I doubt it would work at all, if for long before blowing up.

I also have a capacitor bank of around 30 300 volt camera flash capacitors, if I can make something to charge that easily, that might work after a few pulses, after all I designed that bank for a coil gun.
VOLTS has nothing to do with it, its about current, and number of turns.
iceng4 years ago
Of course an AC relay coil can be powered by AC.
That does not work the other way DC NOT to AC is full of Smoke !

You are mixing the coil properties with the contact abilities.
The whole idea of relays is a small bit of energy controls a greater energy with isolation.

A relay that can switch a capacitors energy to a bunch of wire turns around a screwdriver needs to handle an initial 100 amps or more,
if you expect to use the contacts more then once without the points welding closed.

You need to use an SCR (Silicone Controlled Rectifier)  Thyristor in series between the capacitor and the magnetizing wire coils.
You can use an AC Triac in place of an SCR.  The triacs are not available in heavy currents as SCRs.
Most semiconductors can handle pulse energy in excess of the rated current  making it ideal as a megnetizing switch, still you need a 200A 500V device.

Silicone controlled rectifier ? The ones that bounce when you drop them, or the waterproof ones......
Pulse magnetisers need hundreds of amps flowing usually to work well. The little tiny relays you have are going to weld the first time you use them. This kind of work would need a "contactor", which is effectively a very big relay for switching on motors.
samaddon4 years ago
I THINK IT COULD BE DANGEROUS! Cause the rating on all your relays are less that you DC voltage and it may could blow the relay but i am not confirm cause i don't mess with these relays i use power switching transistors!
XOIIO (author)  samaddon4 years ago
Unfortunately I do not have any switching transistors that can take this kind of voltage, and am looking for something to throw together quickly. I still haven't been able to find anything online about the differences between ac and dc relays, the most I have found is when they are triggered by ac or dc, not the switching mechanism.
samaddon XOIIO4 years ago
See this transistor hope it helps you can buy this one it costs around 1 to 2 dollar in my country and wait i don't know much about relays but i know about transistors!
samaddon XOIIO4 years ago
let me search for this type of transistor wait!