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DC motor - PLC protection

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demirural

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I am running a PLC and a 2Kw 24V dc motor from the same acumulator. but when the motor starts the plc trips to stop. I believe the easiest way to over come this problem is to mount a capacitor but I cannot figure out the specs for it. how can ı calculate what my need is.or have any better ideas or any solutions other than this?
 
demirural said:
I am running a PLC and a 2Kw 24V dc motor from the same acumulator. but when the motor starts the plc trips to stop. I believe the easiest way to over come this problem is to mount a capacitor but I cannot figure out the specs for it. how can ı calculate what my need is.or have any better ideas or any solutions other than this?

2Kw at 24V is 83 amps!, assuming that's running current?, then the start current could easily be a few hundred amps - how big (VERY BIG!) is your accumulator?.

A capacitor to try and provide the current required would be absolutely HUGE - a better way would be to diode isolate the supply to the PLC, and fit a large capacitor on the PLC, to keep that running for a while when the 24V drops way down!.
 
NOT only that but the capacitor will add its own in-rush current to the system which will compound the situation

Two option

1) in-line inductor to limit the current. This will effect dynamic performance
2) Since it is a startup problem, has a resistor in series with the DC-machine and after a set period (controlled by some other means) have a relay short out the resistor, thus bypassing it
 
The acumulator is a 280 amp/hour array of 2V acumulators ( the ones that they use in tow trucks) I will try the series resistor which is some what easier to apply for me. I am still open to suggestions though.
 
demirural said:
The acumulator is a 280 amp/hour array of 2V acumulators ( the ones that they use in tow trucks) I will try the series resistor which is some what easier to apply for me. I am still open to suggestions though.

As I suggested before, diode isolate the power to the PLC, and hang a big capacitor on the PLC (which will keep the PLC powered when the batteries drop briefly).
 
Nigel Goodwin said:
demirural said:
The acumulator is a 280 amp/hour array of 2V acumulators ( the ones that they use in tow trucks) I will try the series resistor which is some what easier to apply for me. I am still open to suggestions though.

As I suggested before, diode isolate the power to the PLC, and hang a big capacitor on the PLC (which will keep the PLC powered when the batteries drop briefly).

I agree with that suggestion.

JimB
 
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