# Electromagnet overheating?

#### 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:

#### Brownout

Joined Jan 10, 2012
2,390
I don't read German. But, it might be the unit is made for short operation. Look for a specification for "Duty Cycle"

#### #12

Joined Nov 30, 2010
18,210
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.

#### 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

#### #12

Joined Nov 30, 2010
18,210
Darn! Missed again.
Here is the right page:
Duty cycle = 100%

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#### 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
18,210
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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#### 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
7,014
This may be obvious, but if you reduce the temperature rise (without a heat sink), you will reduce the pull strength.

#### electronis whiz

Joined Jul 29, 2010
512
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.