KWh Calculation

[ratheepkrk]

Hello,
Please help me to calculate the single phase and three phase motor KWh.

 

[malcolmsanford]

Time my old mate the sooth came back for a visit, so the question is .....................................

Come on son gives us a little clue is it a big motor or a little motor, is it a nice blue one, or that horrible grey type, does is go whirrrrrrrrrrrrrr or hummmmmmmmmmmmmmmmm,

 

[Doomed]

Your answer is 42







What was the question again?

 

[ezzzekiel]

are you sure? my calculation showed 41

 

[malcolmsanford]

Ezze did you take in account the angle of the dangle or the heat of the meat, if you do and then √it by Π taking of course the coefficient of 0.35268 and then multiplying by the root factor of 0.09841 then you can see it is as Doomed said ..................42

But I can see where your coming from mate

 

[telectrix]

well, i got 72.7, but calculated it as 3 phase.

 

[warrenhamlin]

a problem with 11kw motor.
needs a 15kw star/delta starter have got
overload contacts rated 18-24amps
motor start up in star 20.4 amps
running in delta 11.8 amps

the manufacturer has told me that it is a beast to start due to the high currents needed , they suggest fuses, a bit difficult as all distribution boards are circuit breakers. allowing for 6x start up current, can anyone suggest what rating circuit breaker and what type to use

 

[Marvo]

Not sure if understand your exact setup here. The overload needs to be set closer to the run current. An overload set at 18A with a run current of 11.8A leaves the motor wide open to overload damage.

Your question about the circuit breaker I would suggest that the MCB would be appropriately sized for the cable it's supplying, not for the load being driven.

 

[warrenhamlin]

o.k. so the overload to be set at 11.8 amps, not a problem
at the moment 4.0mm 3core armoured on a 32amp triple pole type c mcb cannot hold it in. after calculating the size of cable through a software porgramme, there didn't seem to be an issue with the size of cable

 

[i=p/u]

type c , type d ....... at@ 16A

 

[Knobhead]

type c , type d ....... at@ 16A

An 11KW motor at 400V, .85PF and 90% efficiency comes to 20.2A FLC. For star / delta the O/L should me set to 20.2 / √3 = 11.7A. A bit bigger MCB I think.

 

[i=p/u]

no door number on building, i dont have a clue

 

[warrenhamlin]

i was thinking of a 32amp type d triple pole mcb (merlin gerin)
i had a similar problem with a three phase compressor (again no help from the supplier and manufacturer!)

 

[Knobhead]

You should get away with it. At the end of the day the MCB is to protect the cable, the O/L’s motor.
There’s a lot to commend motor fuses.

 

[Marvo]

I would also imagine a 32A D-curve MCB would be fine in this application.

If the motor is dirving a fairly constant load I wouldn't be afraid to check the actual running current with a clamp meter and set the thermal overload even lower the calculated 11.8 Amps if you can. I tend to err on the side of caution and set them as close as possible.

I also try to spec the thermal so the setting is toward the upper end of it's range that way if some muppet twiddles with it there's still a good chance it will do its job even on its highest setting. In this case I would go with a 7-13A overload rather than one with a range of 11-16A for example.