Rectifiers

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bonding jumper

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I can't find any info about how to protect these devices in the NEC, My intuition says to treat them similar to a transformer, and I can protect the primary as long as the secondary is within 125 percent, but because rectifiers are not covered, I wonder if I might be required to do protection on both sides. Any ideas? Also, when sizing for a motor load, perhaps an elevator, should I size the rectifier to the FLA or the inrush? I was gonna go 125% of the fla, how does that sound? Thanks inadvance
 
Re: Rectifiers

Bonding Jumper, I will try to help you out. I design 48 and 24 VDC battery plants, and the NEC does not offer much info.

Are batteries involved??

The AC input side is protected by the EGC. No special requirements. However the DC output should be complete isolated from the input and equipment cabinet. Therefor you will be required to treat the output much like a transformer. The return lead (either neg or pos) will need a GEC based on the output conductor size.

The rectifier output should be protected by a breaker or fuse, and the EGC for the DC equipment ground conductor will be based on the OCPD at a minimum. However I am not sure what voltage you are using. If it is a low voltage system you will probable want a EGC and load conductors larger than that required by the NEC.

You mentioned elevators, I am not familiar with that type of application, so I may be off base.

Hope that helps. Dereck

[ January 19, 2004, 03:47 PM: Message edited by: dereckbc ]
 
Re: Rectifiers

Many old buildings in NYC have DC services and DC elevators, primarilly just service elevators, not passanger. To convert these and eliminate the need for a dc service, people install rectifiers to convert ac to 240 volt dc. I beleive there are current limiting fuses integrated with the rectifier itself.
 
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