Phil Corso
Senior Member
- Location
- Boca Raton, Fl, USA
Weressl...
Josh said he had 2400V switchgear available.
Regards, Phil
Josh said he had 2400V switchgear available.
Regards, Phil
Weressl...
Josh said he had 2400V switchgear available.
Regards, Phil
The "motors are scarce" part surprizes me. As was mentioned, it is just a matter of connecting the coils Wye or delta. I don't think I have ever seen a 2400V, 4160V, 480V (over 250Hp) that is 'off-the-shelf". No matter which voltage one chooses the motor is going to be built.Again, 2400V systems are becoming obsolete and motors are scarce. 4000V.
[*]Technicians must be MV qualified to work on the gear. ...
I keep hearing this but I never get any reference as to exactly who is mandating this qualification or what it amounts to....Your comment about MV-qualification of techs' is almost verbatim to what I was told when I presented my study to raise HPI-plant LV-distribution voltage from 480V to 830V! ...
I keep hearing this but I never get any reference as to exactly who is mandating this qualification or what it amounts to....
OSHA.
Got this from an inspector once with regards to a project where we installed some MV soft starters, and the City got dinged for not having a "qualified worker" to deal with them.
"29CFR1910.269(x) defines a qualified person as ?one knowledgeable in the construction and operation of the electric power generation, transmission, and distribution equipment involved, along with the associated hazards.? OSHA 29CFR1910.269(a)(2)(ii) also requires that qualified persons ??shall be trained and competent in the skills and techniques necessary to distinguish exposed live parts from other parts of electric equipment; the skills and techniques necessary to determine the nominal voltage of exposed live parts; the minimum approach distances specified in this section (1910.269) corresponding to the voltages to which the qualified employee will be exposed, and proper use of the special precautionary techniques, personal protective equipment, insulating and shielding materials, and insulated tools for working on or near exposed energized parts of electric equipment.?
Yes. It's just that you can get qualified on 600V when you get an electrical license. MV certification is a separate course that not all electricians take. In the case where I learned this, the City had to send one of their staff electricians to get certified. When he was done, he demanded (and got) a raise. Smart cookie...Let's clarify this. OSHA requires qualified workers for all voltage levels, not just Medium Voltage.
No, that's not true.Yes. It's just that you can get qualified on 600V when you get an electrical license. ...
The word "involved" tells me the qualification is equipment specific. Having a COF does not automatically grant "qualified" status for any equipment 600V and under. I'm absolutely not knocking the electricians. There is plenty of screwie stuff out there that one would have to be somewhat nutz to crawl into without special training - and the special training may only be reading the book. But once the training is documented (slip of paper in the file), that's called qualified...."29CFR1910.269(x) defines a qualified person as ?one knowledgeable in the construction and operation of the electric power generation, transmission, and distribution equipment involved, along with the associated hazards.?
Exactly. And the city should have gotten slapped for even considering sending in a maintenance tech without special training on the specific equipment. That is, qualified for the specific equipment - not a general MV certification.... Got this from an inspector once with regards to a project where we installed some MV soft starters, and the City got dinged for not having a "qualified worker" to deal with them. ...?
...Exactly. And the city should have gotten slapped for even considering sending in a maintenance tech without special training on the specific equipment. That is, qualified for the specific equipment - not a general MV certification.
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jd -I would suggest that a "general MV training" does have some merits, ...
Whether you decide to use 500HP @ 480V or 1000HP @ 480V, you need to consider the fact that motor will overheat which could increase the failure time. Refer to IEEE std 620 (thermal Limit curves) for further information.
There are other factors that should be considered as well like replacement strategies, delivery time of a new motor/availability of motor during downtime etc...
Jean-Jacques Ahounou, PE
I am looking into capacity now on 480v switchgear.
Really? I didn't know that. Where exactly does the NEC say that? Please cite article numbers.Not enough.
Perhaps you were misled.
For a maximum size of 500 hp motor, minimum transformer size is 2.5 MVA at 480V . The total load shall not exceed 2.0 MVA per NEC.
Not enough.
Perhaps you were misled.
For a maximum size of 500 hp motor, minimum transformer size is 2.5 MVA at 480V . The total load shall not exceed 2.0 MVA per NEC.
Seems to be maybe some sort of misunderstanding perhaps?
Really? I didn't know that. Where exactly does the NEC say that? Please cite article numbers.
ice
I did not know there were any minimum sizing requirements for transformers to be found in the NEC. Where might I find them?
Searching the term "MVA" only returns one result for the entire NEC pdf that I have, and that has nothing to do with maximum sizes.
The closest I could come to this concept is that in 240.2, the definition of an "Industrial Facility" for purposes outlined in part VIII of that section must be 2500kVA (2.5MVA) or greater, which then indirectly implies that anything UNDER that 2500kVA level does not qualify. No idea how that all fits in with what this discussion is about, but my curiosity was raised as to where that comment came from. Seems to be maybe some sort of misunderstanding perhaps?
Fundamental.....
Hmm..
Which NEC rule says the load current of an equipment not to exceed 80% of its current carrying capacity?