Solid state AC switching? Or wet location contactor?

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fastline

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midwest usa
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Engineer
We have a safety device we are trying to design which will interrupt a motor load if we detect abnormal behavior. The issue is the space constraints as well as a wet location.

Just so people can understand the the issue, the breaker may be 200-300ft from the motor, and we need to 'automate' the interruption. This is NOT considered a disconnect, just need to get the motor offline until it can be manually disconnected and inspected.

The normal mode of the device is preferred to be N.C., but really the only reason for that is to not force the device to have to handle continuous across-the-line starts for no reason. However, we may not be able to avoid this as there would not be any power at the motor location until it is sent to start the load.

Motor size will range from .5-2hp primarily, all single phase applications.

If we could find a way to do this with solid state components, it would be great and I believe the standard for this is a triac with electronics to only allow for zero cross switching? I realize that won't eliminate the inrush hit however. I just don't see solid state used much in this way so I feel I might be missing something.

Or if there are any other thoughts on creating a motor interruption, I am open ears! I know this chat is probably a stretch.
 
What normally switches the motor on/off? It would probably be better to incorporate this logic into that controller rather than interrupt the motor current directly.
 
The shunt breaker is a great idea. And I do agree that finding another way is likely more practical. However,due to the distance and no feasible way to install control wires (many are direct bury cables), the only possibilities are either power wire communication, or wireless. PLC seems most feasible and easy, but I have zero experience with it, so that 'might' be a deep dive.
 
fastline said:
We have a safety device we are trying to design which will interrupt a motor load if we detect abnormal behavior.
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It sort of depends on what you mean by safety device. If you mean you are trying to protect human beings from death or injury, there are certain requirements for such things.

If you are only trying to protect a device or machine from damage, you can do whatever you want.
 
petersonra said:
It sort of depends on what you mean by safety device. If you mean you are trying to protect human beings from death or injury, there are certain requirements for such things.

If you are only trying to protect a device or machine from damage, you can do whatever you want.
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Good mention. I will clarify that this is intended to save equipment only!
 
petersonra said:
For such a small motor a latching relay in series with the motor might make the most sense. Cheap and easy.
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I do like that idea but have yet to find one that could be adapted for a damp location...? I guess I would envision one with pigtail wires rather than terms. maybe you could point me toward some preferred vendors for such products?
 
fastline said:
I do like that idea but have yet to find one that could be adapted for a damp location...? I guess I would envision one with pigtail wires rather than terms. maybe you could point me toward some preferred vendors for such products?
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As a practical matter you are going to need to put it in a box.
 
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