flak monkey
|
| posted on 4/7/09 at 06:27 PM |
|
|
What size MCB?
Just want to check my logic before I buy....
I need to add buy another MCB for the distribution board in the workshop for my lathe power supply.
Its a 3 phase supply, with Type B (dont know why as the board should be type C for industrial I know....) MCBs.
The motor is rated at 5hp (so 3750watts).
Amps = Power / 1.73xvoltagexPF
So thats about 6amps or there abouts.
My concern is over the start up current, would a 10A type B be enough to not trip out on start up, or should I go to a 15A?
Cheers,
David
Sera
http://www.motosera.com
|
|
|
|
|
RichardK
|
| posted on 4/7/09 at 06:31 PM |
|
|
Can't you put a meter through it and switch it on?
I'd say 10 would be fine though.
Regards
Rich
Gallery updated 11/01/2011
|
|
|
blakep82
|
| posted on 4/7/09 at 06:33 PM |
|
|
interesting. my 3hp compressor takes over 16amps starting up. they said to wire it into a 32amp circuit, and it kept tripping its internal circuit
breaker at 16amps. turns out it should have been fitted with a 32amp one.
eta, thats single phase on my compressor mind, 3 phase is the difference isn't it?
[Edited on 4/7/09 by blakep82]
________________________
IVA manual link http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1081997083
don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
|
|
|
madrallysport
|
| posted on 4/7/09 at 06:45 PM |
|
|
Type B MCB is motor rated
UNDERSTEER is when you hit the wall with the front of the car.
OVERSTEER is when you hit the wall with the rear of the car.
HORSEPOWER is how fast you hit the wall.
TORQUE is how far you take the wall with you.
|
|
|
SteveWalker
|
| posted on 4/7/09 at 07:13 PM |
|
|
You're going to be looking at around 30A on startup, but that's for a very short time. MCB characteristics are related to the allowed
surge for such loads and are type B = 2-5 times, C = 5-10 times surge and D = 10-50 times. You need to be looking at a 10A type C really.
|
|
|
geoff shep
|
| posted on 4/7/09 at 07:33 PM |
|
|
Not sure about your sums - is that some 3-phase thing?
Otherwise, watts=volts*amps. So 3750 watts at 240 volts is 15.6 amps.
|
|
|
MakeEverything
|
| posted on 4/7/09 at 07:39 PM |
|
|
Power conversions for 3 phase are different to single phase. They take Power Factor into consideration also.
Kindest Regards,
Richard.
...You can make it foolProof, but youll never make it Idiot Proof!...
|
|
|
daniel mason
|
| posted on 4/7/09 at 09:27 PM |
|
|
u2u sent mate
|
|
|
flak monkey
|
| posted on 4/7/09 at 10:19 PM |
|
|
Thanks guys, I'll fit a 15A MCB and see how it goes.
Should be ample, even with the Type B MCBs as it should allow at least 30A start up current by the sounds of it.
Thanks again,
David
Sera
http://www.motosera.com
|
|
|
