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Thread: Driving a contactor from a Sevcon Gen4?

              
   
   
  1. #1
    Senior Member __Tango's Avatar
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    Driving a contactor from a Sevcon Gen4?

    Hey folks, I'm sure this has been asked and answered before, but i can't seem to find the answer...

    so i'm switching from a Kelly KBL to a Sevcon Gen4 controller for my hub motor.

    This changes how the signal wiring is done on the bike kind of significantly. The first glaring issue is that the Sevcon drives the contactor coil, however the docs say the following about the pin that drives the contactor:

    This output feeds power to the contactors. The output is at battery voltage.
    This is 120VDC for me right now (and in the future may be up to 148VDC).

    The contactor I have (a tyco EV200) only handles 9-36VDC on the coil. I know the sevcon actually tries to do "smart" things when drive the contactor, so i'm not sure if i should insert a relay into the picture or not. Another issue about a relay is that my 2 minute look on the interwebs didn't find a relay that handles 120VDC on the coil.

    So what should I do here?

    (BTW, yes, i know that the EV200 doesn't play nice with the Sevcon because of the coil economizer, but i can remove the economizer and then it'll work).

    Thanks!
    EVs: 2007 Zapino Scooter, Honda VF500 Conversion (electriceptor.wordpress.com), Red Nissan LEAF SL (Arrived!)

  2. #2
    Not to be taken seriously DaveAK's Avatar
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    Out of curiosity, is that the only option the Sevcon has for driving the coil? I know on the Sevcon Powerpaks it's programmable between battery voltage and 24V (fixed) or 24V and then dropping down to 16V, (it's own economizer I guess).

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    On deathbike we just threw a resistor in series with the contactors coil to drop the voltage to something that wouldn't cook it. There are settings to adjust the voltage it outputs for pull-in (and you can set the pull-in time), and then the hold coil voltage. It's critical your EV200 isn't the type with an economizer circuit built-in if you're going to run it from a Sevcon, otherwise the Sevcon PWM's the input to the economizer circuit, and the circuit freaks out and flutters the contactor which will weld it in seconds if you're pulling current.

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    Empulse R #24 frodus's Avatar
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    Re: Driving a contactor from a Sevcon Gen4?

    Just removing the economizer wont work either. The economizer output is not what you think.

    I'd get an Lev200. It doesn't have economizer. I will get you one at cost if you need it. Then you can either adjust the pwm or use a resistor like Luke said.

    You could use a hvdc relay to switch 12v to the contactor as well but that might be harder to find.

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    Senior Member __Tango's Avatar
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    Thanks guys. Travis, i may take you up on your offer for a LEV200. When i talked to the guys who have done this with the sevcon and the EV200, they talked about how they removed the economizer off of the contactor.

    Also, I combed more through the docs and found this:

    Set the analogue output values at object 6C11h. The value is either a voltage or current depending on whether the output is voltage controlled or current controlled. Values are 16-bit integers with a resolution of 1/256 V/bit or A/bit.
    So, Dave and luke were right, I can set the output to whatever voltage i need. The table where i got the first quote from was a bit misleading.

    Cool. Thanks.
    EVs: 2007 Zapino Scooter, Honda VF500 Conversion (electriceptor.wordpress.com), Red Nissan LEAF SL (Arrived!)

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    Empulse R #24 frodus's Avatar
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    Re: Driving a contactor from a Sevcon Gen4?

    Who has done this with the ev200 and what was the setting? If they have it working its worth a shot

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    Quote Originally Posted by __Tango View Post
    When i talked to the guys who have done this with the sevcon and the EV200, they talked about how they removed the economizer off of the contactor.
    That works for a while, but eventually fails. The contactor coil overheats without the economizer even if you reduce the holding voltage.

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    Quote Originally Posted by __Tango View Post
    So, Dave and luke were right, I can set the output to whatever voltage i need. The table where i got the first quote from was a bit misleading.

    Cool. Thanks.
    You can output whatever voltage you need, HOWEVER, it will fault if the coil resistance is too low. It measures the current of the first little pulse from a 1w series shunt resistor in the coil drive circuit, and if it see's current rise too fast or high, it assumes the coil is shorted, faults out with a "shorted contactor coil" fault. This is why though we had a 48v contactor coil on deathbike, we still had to add a series resistor to enable it to drive the coil without faulting.

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