Electromagnet overheating?

Discussion in 'General Electronics Chat' started by peteruithoven, May 11, 2012.

  1. peteruithoven

    Thread Starter New Member

    May 11, 2012
    4
    0
    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: May 11, 2012
  2. Brownout

    Well-Known Member

    Jan 10, 2012
    2,375
    998
    I don't read German. But, it might be the unit is made for short operation. Look for a specification for "Duty Cycle"
     
  3. #12

    Expert

    Nov 30, 2010
    16,343
    6,828
    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.
     
  4. peteruithoven

    Thread Starter New Member

    May 11, 2012
    4
    0
    If I translate the table:

    Code ( (Unknown Language)):
    1.  
    2. Coil data
    3. Relative duty cycle (percent)                   100    50    25    10
    4. Maximum duty cycle (seconds)                    ∞      -     -     -
    5. Max Power (Watts) at 20 ° C coil temperature     2.5
    6.  
     
  5. #12

    Expert

    Nov 30, 2010
    16,343
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    Darn! Missed again.
    Here is the right page:
    Duty cycle = 100%
     
  6. peteruithoven

    Thread Starter New Member

    May 11, 2012
    4
    0
    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?
     
  7. #12

    Expert

    Nov 30, 2010
    16,343
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    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.
     
  8. peteruithoven

    Thread Starter New Member

    May 11, 2012
    4
    0
    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.
     
  9. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    657
    This may be obvious, but if you reduce the temperature rise (without a heat sink), you will reduce the pull strength.
     
  10. electronis whiz

    Well-Known Member

    Jul 29, 2010
    519
    27
    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.
     
  11. Brownout

    Well-Known Member

    Jan 10, 2012
    2,375
    998
    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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