Arc Suppression for large discharge

[moregas]

Hi,
I was thinking to build arc suppression circuit, one for each of the three contacts, for a three phase motor contactor. I was thinking of a RC circuit. The motor (Refrigerant compressor) information, guessing, is about- 20 H.P., 480 ACV, starting current is three or four times running current, and current changes with load.
Please give me your thoughts on this idea. One or two seconds, RC delay should be ok? Also need some good formulas for capacitor and resistor sizes. Thank you.

moregas

 

[waross]

The economizers may have been a scam. They were an inline orofice that was installed ahead of the expansion valve. Less refrigerant delivered made the cooling less efficient. The compressor ran longer with less load. (And if you were using pressure control on a food case, instead of temperature control, the product temp would probably be higher.)
These were sometimes installed at no charge on the basis of a percentage of the electric bill savings over the next year.
The target market was supermarket food cases.
I saw the brochures but never saw one up close and personal. As I remember they were about the size of a small inline check valve.
How about a suction restriction? I used to watch the operators bringing down ammonia systems by throttling the suction valve until the cols or whatever were down to normal temperature. If they didn't throttle, I would trip the breaker and crash their system. Then I would remind them that the motor was overloaded, smoking hot and about to burn out.
The first time I did it the manager tore a strip off my a$$.
I explained the facts of life to the manager and the next time he tore a strip off the operator.
But if your compressor can take more negative pressure, suction throttling may help.
Longer run time;
If you reduce the load on a system, so that the kiloWatts drawn by the motor is less, the longer run time may not cost much.
For VFDs, I suggest you start a new thread and ask specifically for help applying a VFD. Apologize to skogsgurra. He is one of the VFD experts. jraef is also very good. We have a few other experts that drop in from time to time.
There are two issues with applying a VFD. One is the electrical issues, the other is the refrigeration issues such as oil transit. You may want to post a question in a refrigeration forum also. Don't post the same question in both fora.
You know better than I, but if you go with a VFD can you kick the system up to 60Hz once a day to flush the oil from the lines?
On the other hand, an over sized starter from Allen Bradley or Square D may solve your problems.

Bill
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"Why not the best?"
Jimmy Carter