Electro magnet design

[Gregory]

I have been researching 240 v electro magnet but after getting the feedback from this sight that it has problems with the design.
I have now changed my mind and going with four 12 v dc auto compressors Magnets .
They have about 15 AMP current draw.
How will I go about connecting the 4 magnets to get her and 12 v dc supply and the current required NOT using a battery.
But using 240 v reduced to 12 VDC

 

[rjenkinsgb]

You need a 12V power supply with a high enough total current rating to power the magnet coils. If that's 15A total for them all, than a supply rated at something over 15A.

If it's 15A each, you would need 60A at 12V. Using two series pairs would probably be more practical then, making it 30A at 24V.

 

[unclejed613]

the best bet for this, expense wise as well as availability would be to get a power supply for automotive audio or amateur radio equipment. 12V @60A can be supplied by paralleling 4 12V@15A supplies, or driving each coil with a separate supply. such power supplies are fairly common because 12V audio and amateur radio equipment are common. 12V is the most commonly used DC supply voltage worldwide. for amateur radio equipment there are some 12V supplies that are in excess of 60A output, but those ones will be rather expensive. however 12V@15 or 20A are very common as they get used a lot for car audio sales departments in large retail stores.

 

[Gregory]

Does the magnet require a pure DC supply

 

[alec_t]

That depends on the intended use of the magnet.

 

[dr pepper]

A/c compressors most likely will require Dc, even industrial clutches & brakes are usually Dc.
Also they may not be rated for continuous operation, you'd have to see if you can find any data for them, or just put tone on test & see how warm it gets.

 

[Nigel Goodwin]

A/c compressors most likely will require Dc, even industrial clutches & brakes are usually Dc.

Where I used to work we had a small goods lift/hoist (since gone to the scrap yard), it was three phase and had an electromagnet that pulled the brake shoes off during use. The electromagnet was an AC one.

 

[MaxHeadRoom78]

Does the magnet require a pure DC supply

You should be OK with a Bridge rectified 12vac, generally a smoothing cap is not needed for electromagnetic devices like this.
Max.

 

[dr pepper]

Yes brake drums with shoes had Ac coils, I havent seen one for ages, they went out with Ww2.

 

[Nigel Goodwin]

Yes brake drums with shoes had Ac coils, I havent seen one for ages, they went out with Ww2.

It was pretty old

But it did a lot of good work over the years.

I'm not sure when it was fitted, but I'm presuming it was the 60's - funnily enough a couple of years ago the guy who fitted it happened to come in the shop, and he was saying what a hard job it was to fit as they had to make a hole for it through the concrete floor/ceiling.

 

[dr pepper]

I've never had much to do with lifts, overhead cranes can be tough to fit, esp when theres no room to lift them, you have to push them up.