PROTECTIONS

[j-santia]

Hi, I need some information about protections related with low voltage. I'm very confused and I don't knlow what kind of protections i should use, and also I want to know what are the different kind of loads, for example in an industry or a comercial building.

thanks a lot of.

ulises

 

[charlie b]

Re: PROTECTIONS

1. What do you mean by "low voltage"? Some use that term for under 600 volts, and others use that term for telecommunications and security systems.

2. What do you mean by "protections"? Are you asking about fuses and breakers to protect cables, or about thermal overloads to protect motors, or about mitigation systems to protect electronics against harmonics, or something else?

 

[tom baker]

Re: PROTECTIONS

Call Mike Holts office and order Understanding Low Voltage and Limited Energy systems. There is also a video that goes with it.
If not, then you'll need to review Art 725 in the NEC, otherwise known as the Mother of All Low Voltage Articles. Keep in mind there is no definition of Low Voltage in the NEC. Explaining the NEC rules for low voltage on this forum is not practible. Get Mikes text, and then let us know if you have any questions.

 

[j-santia]

Re: PROTECTIONS

Low voltage I refer to voltages under 600 volts.

I talk about protection related with the mitigation systems to protect electronics against harmonics

Originally posted by charlie b:
1. What do you mean by "low voltage"? Some use that term for under 600 volts, and others use that term for telecommunications and security systems.

2. What do you mean by "protections"? Are you asking about fuses and breakers to protect cables, or about thermal overloads to protect motors, or about mitigation systems to protect electronics against harmonics, or something else?

[ October 15, 2003, 04:36 PM: Message edited by: j-santia ]

 

[dereckbc]

Re: PROTECTIONS

Originally posted by j-santia:
I talk about protection related with the mitigation systems to protect electronics against harmonics.

If you are referring to cleaning up or filtering harmonics, there are three methods that range from extremely effective to moderately effective in the order of:
1. Motor generator
2. UPS
3. Ferroresonant voltage regulator transformer.

If are referring as to how to contain or localize harmonics to a particular distribution system, a delta/wye isolation transformer is a common method.

But I am not sure that answers your question. Harmonics are generated by the very electronic systems you are trying to prevent them from reaching. The problems of harmonics are greatly over exaggerated. If you know from the start that you are going to have non-linear loads, then the design should take that into consideration, rather than after the fact. And in today?s modern electronic world, I consider every design to supply non-linear loads.

It is more technically correct to say "how you are going to protect your electrical system from harmonics", rather than the equipment that generates it.

[ October 15, 2003, 09:06 PM: Message edited by: dereckbc ]