Picture of proper diode installation on SW200 contactor?
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Mike Brown
Jul 5, 2011, 11:03:26 PM7/5/11
to 914ev
My contactor came from ElectroAuto separate from the diode, so I've
been searching for the proper way to install it on the small terminals
of the contactor.
Many vendors use this same picture
http://store.kta-ev.com/contactors_and_battery_disconnecting_switches/albright_sw200b_contactor.aspx
which shows the diode installed, but of course it could be wrong. I
see that the diode is mounted under the (-) terminal, with the band at
the top. I just want to make sure before something catches on fire...
Thanks!
Mike Brown
No, not him, another one.
been searching for the proper way to install it on the small terminals
of the contactor.
Many vendors use this same picture
http://store.kta-ev.com/contactors_and_battery_disconnecting_switches/albright_sw200b_contactor.aspx
which shows the diode installed, but of course it could be wrong. I
see that the diode is mounted under the (-) terminal, with the band at
the top. I just want to make sure before something catches on fire...
Thanks!
Mike Brown
No, not him, another one.
Jerry Pohorsky
Jul 6, 2011, 2:39:53 AM7/6/11
to 91...@googlegroups.com
Hi Mike,
The picture is correct.
The +12 volt side of the coil goes to the band end of the diode (known as the cathode).
If you had it connected the other way, the diode would conduct and you would essentially have a short circuit.
The diode would probably explode instead of catching fire.
I've seen diodes like this explode before with a big bang. Pieces of epoxy go flying at high velocity.
The function of the diode is to conduct when the coil is turned off and look like an open circuit when the coil is on.
This will dissipate the energy that is generated as the magnetic field in the coil collapses after the 12 volts is removed.
Without the diode, the voltage spike that occurs when the coil is turned off will eventually damage the chip that drives the contactor coil. This diode suppresses that voltage to a safe level.
This is a rather common technique with any DC coil relay or contactor.
There are other suppression circuits that are more sophisticated, but this one usually works well enough.
Adios,
Jerry Pohorsky
former EV-914 owner
The picture is correct.
The +12 volt side of the coil goes to the band end of the diode (known as the cathode).
If you had it connected the other way, the diode would conduct and you would essentially have a short circuit.
The diode would probably explode instead of catching fire.
I've seen diodes like this explode before with a big bang. Pieces of epoxy go flying at high velocity.
The function of the diode is to conduct when the coil is turned off and look like an open circuit when the coil is on.
This will dissipate the energy that is generated as the magnetic field in the coil collapses after the 12 volts is removed.
Without the diode, the voltage spike that occurs when the coil is turned off will eventually damage the chip that drives the contactor coil. This diode suppresses that voltage to a safe level.
This is a rather common technique with any DC coil relay or contactor.
There are other suppression circuits that are more sophisticated, but this one usually works well enough.
Adios,
Jerry Pohorsky
former EV-914 owner
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Mike Brown
Jul 6, 2011, 10:36:09 AM7/6/11
to 914ev
Thanks for the confirmation and the background Jerry!
Mike Brown
No, not him, another one.
> >http://store.kta-ev.com/contactors_and_battery_disconnecting_switches...
Mike Brown
No, not him, another one.
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