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3 phase motor compensation capacitors
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| colinstone@hotmail.com 2007-04-09, 5:25 pm |
| I have a 5.5kW 400v 3 phase AC motor. Can anyone help with the
calculation to work out the size of the compensation capacitors.
TVMIA.
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| operator jay 2007-04-09, 8:25 pm |
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<colinstone@hotmail.com> wrote in message
news:1176157440.420311.206660@q75g2000hsh.googlegroups.com...
>I have a 5.5kW 400v 3 phase AC motor. Can anyone help with the
> calculation to work out the size of the compensation capacitors.
> TVMIA.
>
The more info you give on the motor, the better the caps can be sized.
Based on efficiency of 93% and a pf of about 88%, 3 kVAR caps (1 kVAR
per phase) may be okay. There are a number of things you can screw up
by using capacitors, I hope you know what you are doing.
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| colinstone@hotmail.com 2007-04-09, 8:25 pm |
| >I hope you know what you are doing.
Nope - hence the question!. Motor will be used to power a bow
thruster, so must be reversing. Efficiency is likly to be around 93%
- not yet bought. Friend has a 5.5kw motor DOL on a 10kw genset - so
aiming to do the same.
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| Salmon Egg 2007-04-10, 3:25 am |
| On 4/9/07 4:48 PM, in article
1176162513.175284.299640@o5g2000hsb.googlegroups.com,
"colinstone@hotmail.com" <colinstone@hotmail.com> wrote:
>
> Nope - hence the question!. Motor will be used to power a bow
> thruster, so must be reversing. Efficiency is likly to be around 93%
> - not yet bought. Friend has a 5.5kw motor DOL on a 10kw genset - so
> aiming to do the same.
>
>
Why do you need to compensate at all? Why not just take the hit on power
factor?
Bill
-- Fermez le Bush--about two years to go.
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| Paul Hovnanian P.E. 2007-04-10, 3:25 am |
| colinstone@hotmail.com wrote:
>
>
> Nope - hence the question!. Motor will be used to power a bow
> thruster, so must be reversing. Efficiency is likly to be around 93%
> - not yet bought. Friend has a 5.5kw motor DOL on a 10kw genset - so
> aiming to do the same.
What will the power source for this motor be? A VFD for speed control
perhaps? That will change the answer significantly.
--
Paul Hovnanian mailto:Paul@Hovnanian.com
------------------------------------------------------------------
There are only 10 kinds of people in this world,
those who understand binary and those who don't.
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| operator jay 2007-04-10, 3:25 am |
|
<colinstone@hotmail.com> wrote in message
news:1176162513.175284.299640@o5g2000hsb.googlegroups.com...
>
> Nope - hence the question!. Motor will be used to power a bow
> thruster, so must be reversing. Efficiency is likly to be around
> 93%
> - not yet bought. Friend has a 5.5kw motor DOL on a 10kw genset -
> so
> aiming to do the same.
>
>
I think it's time to hire an electrician, you have managed to end up
with all the concerns of and between gensets, capacitors, starters,
motors and motor starting, in this one little installation.
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| colinstone@hotmail.com 2007-04-10, 5:25 pm |
| Bow thruster motor 3ph 400V 5.5kW will be driven by 11.3 kW 3000rpm
Fischer Panda genset. Motor will be 4 pole and will be either on or
off - I do not need to change motor speed. Options seems to be:
DOL starting - friend has a 2 pole 5.5kw motor DOL on a 10kw 1500 rpm
genset.
DOL with motor compenstaion to bring PF back to 1, or as near as
possible.
Soft starter.
VFD drive.
TVMIA
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