My application is as such.
1. Electromagnet is moved to workpiece.
2. Electromagnet is switched on, and holds on to workpiece.
3. Electromagnet is switched off.
4. Electromagnet is moved rapidly away from the workpiece.

My issue is massive arcing across the relay contacts.

I've already looked into snubbers to control the arcing, but I think a large part of the problem is that I am moving the magnet away rapidly and this is causing, due to residual magnetism in the workpiece, the electro-magnet to turn into a generator, causing another spike.

<b> Any thoughts, ideas, etc, on how I can help eliminate the spiking? </b>

Note - Someone else before me setup a snubber with a 7700uF cap and a 8.2ohm 3watt resistor, but they wired it in very strangely; it doesn't make sense to me

Note 2 - efficiency isn't an issue, heat isn't really an issue, has to be done as fast as possible

Disclaimer - I was trained in electromechanical, but it was pretty much mechanical & PLC's. So, I'm a bit new in this area....

Thanks kindly

 

XC_racer... any Electro-magnet details you can provide will be helpful.

Regards, Phil Corso

 

the usual solution is to put a diode in parallel with the coil such that when the coil is energized the diode is reverse biased.

on breaking the dc circuit, the coil discharges with reverse polarity through the diode.

the peak current is equal to the max dc current when the coil is energized. if your diode needs further current limiting, then put the 8.2 ohm resistor in series with it.

snubbers (r/C type) can also work if wired up properly, but there is always a risk when you put a capacitor in an inductive circuit, if it is not properly sized.

 

D-... a diode, unless a Zener-type, installed in parallel with the coil, will decrease the current decay-rate, i.e, increase load-release time.

Phil Corso

 

good point the 8.2 ohm mentioned in the original post will help with the L/R time constant. one wonders why a relay if response time is such an issue,

> ... a diode, unless a Zener-type, installed in parallel with the coil,
> will decrease the current decay-rate, i.e, increase load-release time.

 

D- ... I asked Packzod for additional detail regarding his problem because it is correctable!

Regards, Phil

 

XC-racer... sorry that my 31-Oct-11 (14:07) was improperly addressed.

BTW, there are formulas for RC (snubber) circuits. And, there are also solutions involving diodes, Zeners, and Varistor components. Of course the latter require that nameplate data also be made available.

Regards, Phil Corso (cepsicon[at]AOL[dot]com)

 

my issue is electromagnet is connecting the drive shaft when power cut. it is continuously hold. how to solve the problem.

thanks

 

since your matter significantly differs from the original post, you'll have to explain what your mechanical arrangement is. and some details as to what the solenoid is supposed to do and how it is failing that intended operation.