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3 years 3 months ago #29532329 by cory944
pre charge resistor was created by cory944
Dear Roboteq technical support,

I'm using a power relay to connect 48v battery bank with FLB2360 (Vmot), relay is spdt. I'm using the relay's common pin to connect to Vmot, "NC" pin to battery negative and "NO" pin to connect to battery positive. I'm using a pre-charge resistor, one lead is connected to battery positive and the other lead to relay's common pin (Vmot). But since I'm using spdt relay and "NC" pin is connected to battery negative then when controller is off the pre-charge resistor's lead that is connected to relay's common pin (Vmot) would be connected to battery minus so capacitors would not charge, right?

If so, do I use a diode between relay's "NO" pin (battery positive) and common pin (Vmot)?

Please guide me.

Thanks in advance,
Victor

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3 years 3 months ago #29532334 by cory944
Replied by cory944 on topic pre charge resistor
Dear Roboteq technical support,

I would really apreciate your help.

I hope you can help me.

Regards,
Victor.

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3 years 3 months ago #29532335 by blake
Replied by blake on topic pre charge resistor
Hello again Victor,

Please accept my apology for the late reply.

The conditions that will allow the controllers caps to precharge are as follows:

1) PwrCtrl is shorted to ground.
2) PwrCtrl voltage is greater than Vmot voltage.

If PwrCtrl is left loating or Vmot > PwrCtl then the capacitors will not pre charge. Additionally if VMOT is shorted to controller GND then this will effectively short the capacitors and they will not precharge.

You can insert a 1K, 0.5W resistor accross your switch to allow the capacitors to slowly charge. See "Using a Precharge Resistor" on page 25 of our user manual for more details.
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3 years 3 months ago #29532336 by cory944
Replied by cory944 on topic pre charge resistor
Hi Blake,

Thank you for your reply. You're always helping me.

Yes I have read manual. But I wanted to be sure about caps not charging when Vmot is connected to gnd when controller is off.

So, since I'm using a spdt relay and Vmot is connected to gnd when controller is off in effect caps won't pre-charge.

Is it possible to "extend" the regeneration diode I'm using to Vmot? Or is there another method I can use to avoid transient when I turn Controller (Vmot) on?

I really aprecite your help.

Regards,
Victor.

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3 years 3 months ago #29532337 by blake
Replied by blake on topic pre charge resistor
Yes that is right, if VMOT is grounded then the caps won't pre-charge.

You can extend the diode across your switch to VMOT then it will act as a flyback diode for transients.
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3 years 3 months ago #29532338 by cory944
Replied by cory944 on topic pre charge resistor
Dear Blake,

Thank you very much.

Sorry for the basic questions I always ask and believe me I read the manual but I wanted to be sure before I continue with my projects.

Regards,
Victor.

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3 years 3 months ago #29532339 by blake
Replied by blake on topic pre charge resistor
There's no such thing as a basic question, its good practice to be sure! Let us know if you have any others
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