Then your daigram is incorrect.
Power factor correction capacitor sizing for a wye-delta motor connection
- Thread starter fanyu622
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Phil Corso
Senior Member
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- Boca Raton, Fl, USA
FanYu...
Motor PFC should be sized to compensate for about 90% of a motor's no-load current!
Phil Corso
Motor PFC should be sized to compensate for about 90% of a motor's no-load current!
Phil Corso
kwired
Electron manager
- Location
- NE Nebraska
If load is fairly constant why not shoot for desired corrected power factor?
fanyu622
Member
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- montreal, quebec, canada
Hm, why?
fanyu622
Member
- Location
- montreal, quebec, canada
There are different methods of sizing them.
Your method is one way.
I use my selection based on existing and target pf.
Phil Corso
Senior Member
- Location
- Boca Raton, Fl, USA
FanYu...
It has to do with a phenomenon referred to as "self-excitation of a motor upon disconnection from its power supply"! The subject was covered extensively in a Post titled "OverCorrection"!
It has to do with a phenomenon referred to as "self-excitation of a motor upon disconnection from its power supply"! The subject was covered extensively in a Post titled "OverCorrection"!
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The capacitors are shown in star or wye.
kwired
Electron manager
- Location
- NE Nebraska
But capacitor bank is across input voltatge lines anytime the motor is running or starting. It doesn't show any details of individual capacitor component connections.
Phil Corso
Senior Member
- Location
- Boca Raton, Fl, USA
Beesoaker...
But you said, "Um......check the diagram provided by the OP."
Phil
But you said, "Um......check the diagram provided by the OP."
Phil
Did you?
Actually, it does.
fanyu622
Member
- Location
- montreal, quebec, canada
In 3 phase, the 3 capacitors are either connected in wye or delta.
Delta is usually preferred, because you get only 1/3 total VAR from a wye.
Phil Corso
Senior Member
- Location
- Boca Raton, Fl, USA
FanYu...
"Delta is usually preferred, because you get only 1/3 total VAr from a Wye."
Correct, but for a different reason! The delta-connection is less likely to become a problem if source of supply is single-phased!
Do you know the equation to determine capacitance or kVAr... w/o a chart?
Phil
"Delta is usually preferred, because you get only 1/3 total VAr from a Wye."
Correct, but for a different reason! The delta-connection is less likely to become a problem if source of supply is single-phased!
Do you know the equation to determine capacitance or kVAr... w/o a chart?
Phil
You'd use cifferent value capacitors with a different voltage rating in star. Not something I've seen done very often............
fanyu622
Member
- Location
- montreal, quebec, canada
Phil Corso
Senior Member
- Location
- Boca Raton, Fl, USA
FanYu...
Capacitance: Cy = 3 x CD !
Qc (3ph kVAr) = [Sqrt(3) x Vpp x Io]/1,000, where Io = No-Load Current, in Amperes!
Phil
Capacitance: Cy = 3 x CD !
Qc (3ph kVAr) = [Sqrt(3) x Vpp x Io]/1,000, where Io = No-Load Current, in Amperes!
Phil
Phil Corso
Senior Member
- Location
- Boca Raton, Fl, USA
FanYu...
Correction:
Qo (3ph kVAr) = [Sqrt(3) x Vpp x 0.9 x Io]/1,000.
Also, there is no "one-size fits all" value! Rated speed (# poles) impacts Co selection!
Phil
Correction:
Qo (3ph kVAr) = [Sqrt(3) x Vpp x 0.9 x Io]/1,000.
Also, there is no "one-size fits all" value! Rated speed (# poles) impacts Co selection!
Phil
kwired
Electron manager
- Location
- NE Nebraska
You must be getting a different drawing then I am then. All I see is a box with three leads that end at the outline of the box and the box is PFCC and has a single capacitor symbol inside the box as well - no other details of how individual capacitors within that box may be connected.
That said isn't the net KVAR of the unit mostly all we care about?
Phil Corso
Senior Member
- Location
- Boca Raton, Fl, USA
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