mccb lay out

[james king]

hi all


after my thread yesterday i asked my boss how a hw would wire the 50KW motor. the said a 125A mccb??

now if there is 1x 3 phase supply into a building, each pahse has 100A per phase and is then connected into a 3phase board.

does he mean the mccb will replace 1 of the mcbs in that 3phase DB or will it have to have its own supply? eg from DB to SUB DB with a mccb in it then out to the motor??

i will do a diargam and post it

just curous

 

[james king]

just done some research i seee the mccb needs a pannel board? and then the mccb come from there??

now say a DB is all you have what would you do to connect the pannel to the DB e.g run 25mm tails less then 3m away from the main DB? can you get a add on 125A main switch at the top of the DB

 

[james king]

thanks for all your replys lol

 

[sparkydude]

If you have a 100A supply you are not going to get a 125A supply out of it LOL. Most commercial installations of any standing have a main switchpanel of some size , which are most likely fed of off their own local transformer with big cables. The current job i am on has 4 supplies all of 3200A and the mains panelboards for each supply is about 30 foot long,7ft tall and 4ft deep !!!


Nick

 

[james king]

big then mate lol.. so if i take a 50Kw load what will be needed for that? are u saying u will need another 3phase supply? but 125A can be shared by 3phases

 

[Marvo]

A 50KW 4-pole induction motor will have FLA approx 90Amps dependant on efficiency and pf. The 90Amps run current is 90 Amps per phase. Bear in mind this is run current, not start current. You have a DB with 100Amps available. It isn't enough.

 

[james king]

so if i was in a situation like this i would have to ask for another supply ?

 

[Marvo]

I would spec a new 150A supply dedicated for the motor.

 

[james king]

what cables are ussaly use for this king of Kw? 25mm swa?

 

[johnboy6083]

Dependson length of run, ambient temp, installation methods, power factor of the load, type of cable ect.

 

[james king]

so for this type if motor (50Kw) would u then have its own supply say as above said 150A per phase? then have in incoming tails run in a 125A panel with a rccd runing to the motor??

 

[pennywise]

Is this a three phase motor?

 

[james king]

yes!!!

 

[Marvo]

so for this type if motor (50Kw) would u then have its own supply say as above said 150A per phase? then have in incoming tails run in a 125A panel with a rccd runing to the motor??

The RCCD is entirely your call. We don't stock them that size so we don't install them but here in Africa you can do pretty much what you like when it comes to motor control ;-)

 

[pennywise]

125A for a three phase motor sounds a little high sorry just interested to see how big this thing is

 

[james king]

its question from collage!! it says its a biofuel machine. why does it sound to high? we got a leaflet with it explianing specifications cnt remember what is on it? so basicly what you are saying is that u it will need its own supply.

i think it was 415v
50,000W
grouped with 2 other cable
30 degrees
in metal trunking

 

[Marvo]

It would be about 2ft high by almost 4 ft long including shaft and just under 2ft across the hips. Still interested?

 

[pennywise]

It would be about 2ft high by almost 4 ft long including shaft and just under 2ft across the hips. Still interested?

without a doubt just never seen one thanks

 

[james king]

huh back to the Qplz lol hahaha

 

[Marvo]

without a doubt just never seen one thanks

I've never seen a 50 either, only a 55 KW. 50 is a bit of an odd size, they crop up more in text books that in real life, probably cause it makes for easier calcs with round numbers.

 

[james king]

lol ok so with what info i gave you what cable size do u think u would use?

 

[Marvo]

You'll need to figure that out with the regulations for your locale. You start wth a cable that will handle the max load then start penalising for length of cable, how it's run etc etc. I don't have a copy of the UK regs I'm afraid....assuming ur in the UK.

 

[james king]

ok thanks any way