Calculating 3 phase current

[dgrande]

I understand that the formula to work out a 3 phase current is
I= P/(1.732 * V * pf)

I have a 3 PH+N water pump rated at 4kw, so

I= 4000/ (1.732 x 400 x 0.8)

I= 4000/554.24

I= 7.21 Amps per phase

The problem I have is that the label on the pump control says that its rated current is 40Amps, Have I missed something?
thanks

 

[mechelec]

The panel is rated 40A not the pump???
This could be to allow for startup currents???

 

[Marvo]

Also lock rotor LRA I suppose but it makes no sense to me why they'd state that as a rating and not the run current and maybe the max Icu of the internal components in kA.

 

[Paultrim123321]

Sounds like an Italian panel

 

[telectrix]

is york in italy now?

 

[Paultrim123321]

I'm being sarcastic:/ I'm guessing you have never commissioned Italian control systems.

 

[44ALLAN]

15kw pump is 26Amp flc @ 420v....................work it out for 4 kw

ohhh u have lol.

 

[Paultrim123321]

Dgrande your formula is spot on

 

[Marvo]

I have a 3 PH+N water pump rated at 4kw, so

I= 4000/ (1.732 x 400 x 0.8)

If your pump is 3ph+n is it wired in 230v star? This would affect your current.

 

[Engineer54]

Always take notice of the electrical data label on the motor, NOT on the panel controlling the motor!! That panel could be a manufacturers standard panel, that covers many of it's pump/motor sizes etc!!

 

[GMES]

As above always go on the name plate of the pump/motor . I have been on many a brake down in factories arguing with people who have connected a motor wrong ie- star/delta and all they will say is the last one was connected that way so I just copied connection's. Doesn't matter just refer to the nameplate for everything to do with motor you are working on that goes for connections, contactor's, overloads etc.