Electromagnet overheating?

Thread Starter

peteruithoven

Joined May 11, 2012
4
Hi,

This is my first post here, so please tell me if I should clarify anything.

I'm having the problem that my electromagnet is getting very hot and I can't figure out why. I bought the Intertec ITS-MS-2015 from Conrad.

It's a 12V 2.5W electromagnet with a force of 20N.

It's force is really nice (see some experiments). But like I said it get's very hot.
Some data:

Magnet:
R: 70 ohm
U: 21 V
Calculated I (12/70): 0.1714285714 A / 171 A
Documented I (2.5/12): 0.2083333333 A / 208 mA
Measured I: 0.17 A (in 10A mode) en 155 mA (in 200mA mode)

I use a Voltcraft USPS-600 adjustable DC adapter, put on the 12v mode, to power it. It says it can deliver 600mA. I also measured that it's giving about 12V.

When I mean hot I mean you can't hold it in your hands anymore.

Any tips would be greatly appreciated.
 
Last edited:

#12

Joined Nov 30, 2010
18,224
Ich sprec enough Deutch to tell you the duty cycle is not listed but the Tmax is 130 C. Way hotter than a human can tolerate!

If you want to know if it's in danger you are going to have to measure the temperature correctly.
 

Thread Starter

peteruithoven

Joined May 11, 2012
4
If I translate the table:

Rich (BB code):
Coil data 
Relative duty cycle (percent)                   100    50    25    10
Maximum duty cycle (seconds)                    ∞      -     -     -
Max Power (Watts) at 20 ° C coil temperature     2.5
 

Thread Starter

peteruithoven

Joined May 11, 2012
4
So it's heatsinking, lowering the duty cycle (I have to research how), adding a resistor, or just making sure the surrounding parts can handle the heat I guess?
 

#12

Joined Nov 30, 2010
18,224
Yes. Pulse width modulating for a duty cycle control has been done many times on this site but a single resistor or a lower supply voltage will accomplish the same thing. Do you need a schematic for a PWM circuit?

This one has more parts than you need and could be modified if you want to.
 

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Thread Starter

peteruithoven

Joined May 11, 2012
4
Thnx #12, if I can do it using PWM I can probably do it using my Arduino and a MOSFET so I should be okay.

Thanks everybody for the input.
 

Ron H

Joined Apr 14, 2005
7,063
This may be obvious, but if you reduce the temperature rise (without a heat sink), you will reduce the pull strength.
 
id say heat sinking it would be your best bet. in the pic it looked like fairly small electromagnet. i'd try a small heatsink from like a northbridge or old video card from a computer. using one with a fan in it may help a bit also.
a peice of coper pipe about 6inches - 1ft could be a good heatsink fit the magnet in the pipe on one end. the coper should disipater the heat and by the time it travels a ways up the pipe it should be mostly disipated leaving the other end safe to use as a handle.
or find something liquid that will conduct heat but not cunduct like water. vegtible oil posibly or what they use in computer cooling systems.
 

Brownout

Joined Jan 10, 2012
2,390
Just to be clear, when I mentioned duty cycle, I only meant turning off the power and letting the unit cool down every once in awhile. For exaple, I have a welder with a 30% duty cycle. That means if I use it for 20 minutes, I have to let it cool for 40 minutes before using it again.
 
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