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Type B RCDs

M. Joshi
Increasingly, I am seeing a requirement for Type B RCDs in industrial applications, particularly where servo drives are used.


The preference is Type B RCBOs however, these are quite rare and not all manufacturers make them.


Aside from the high cost and short supply due to demand from EV and PV applications, how do others address this situation?


If the earthing is adequate, cables to the motors are run in trays and there is additional bonding to the motor housing, is there really a need for an RCD?
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    In a UK industrial environment, it is very difficult to see the use of RCD protection. Additional protection (and you say servo drives) in a bonded environment and one that is maintained does nothing extra, and something like welding robots would probably make short work of RCDs anyway. The question to ask is "why do I need additional protection? What credible problem or accident could there be where it would make any difference". Additional protection is a good idea for portable appliances and places where human direct contact is credible. In a domestic environment, it probably makes a difference, particularly outdoors. In other places, it may increase danger, say my robot loses power to one motion, and it is working near people (some do) then stopping it instantly becomes necessary. RCDs can trip for many non-dangerous situations, and coping with the results is often difficult, say in conveyors in a food factory feeding an oven. A nuisance trip can cost a lot of money in lost product, but it is unlikely to make the factory safer. RCDs everywhere are far from a universal "safety" feature, they may have no credible function in the chain of actual safety.
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  • 0
    In a UK industrial environment, it is very difficult to see the use of RCD protection. Additional protection (and you say servo drives) in a bonded environment and one that is maintained does nothing extra, and something like welding robots would probably make short work of RCDs anyway. The question to ask is "why do I need additional protection? What credible problem or accident could there be where it would make any difference". Additional protection is a good idea for portable appliances and places where human direct contact is credible. In a domestic environment, it probably makes a difference, particularly outdoors. In other places, it may increase danger, say my robot loses power to one motion, and it is working near people (some do) then stopping it instantly becomes necessary. RCDs can trip for many non-dangerous situations, and coping with the results is often difficult, say in conveyors in a food factory feeding an oven. A nuisance trip can cost a lot of money in lost product, but it is unlikely to make the factory safer. RCDs everywhere are far from a universal "safety" feature, they may have no credible function in the chain of actual safety.
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