Over correction

ptonsparky

Senior Member
Gentlemen...

I want to thank all that were patient. Below is the Table of the 30Hp motor I found. It will be used in subsequent analysis of PtonSparky's case

INDUCTION MOTOR RATED PARAMETERS
Hp
Volts
Amperes
PF
Eff'y,%
# Poles
Hz
Slip,%
Nr
30
460
36.5
0.82
94.1
4
60
1.5
1,173
ELECTRICAL INPUT
POWER DISTRIBUTION in PERCENT
kVA
kW
kVAr
Pin
Pout
Pcu, Str
Pcu, Rr
Pfe
Pfw
29.1
23.9
16.6
100
94.1
1.90
1.70
1.30
1.25

For the Submersible cable parameter I'll use NEC Table 9, for #6, AWG!

Attn Nitpickers: I'm ignoring the imbalance-factor associated with unrolled, flat-cable!

Phil
Now you've opened another can of worms, you can explain at a later date.
 

topgone

Senior Member
Gentlemen...

I want to thank all that were patient. Below is the Table of the 30Hp motor I found. It will be used in subsequent analysis of PtonSparky's case

INDUCTION MOTOR RATED PARAMETERS
HpVoltsAmperesPFEff'y,%# PolesHzSlip,%Nr
3046036.50.8294.14601.51,173
ELECTRICAL INPUT POWER DISTRIBUTION in PERCENT
kVAkWkVArPinPoutPcu, StrPcu, RrPfePfw
29.123.916.610094.11.901.701.301.25

For the Submersible cable parameter I'll use NEC Table 9, for #6, AWG!

Attn Nitpickers: I'm ignoring the imbalance-factor associated with unrolled, flat-cable!

Phil
You might want to edit that. How could a 4-pole motor run at 1173 rpm? :)
 

Sahib

Senior Member
Gentlemen...

I want to thank all that were patient. Below is the Table of the 30Hp motor I found. It will be used in subsequent analysis of PtonSparky's case

INDUCTION MOTOR RATED PARAMETERS
HpVoltsAmperesPFEff'y,%# PolesHzSlip,%Nr
3046036.50.8294.14601.51,173
ELECTRICAL INPUT POWER DISTRIBUTION in PERCENT
kVAkWkVArPinPoutPcu, StrPcu, RrPfePfw
29.123.916.610094.11.901.701.301.25

For the Submersible cable parameter I'll use NEC Table 9, for #6, AWG!

Attn Nitpickers: I'm ignoring the imbalance-factor associated with unrolled, flat-cable!

Phil
May we suppose the no load KVAR of motor to be 25% of its full load KVA i.e 29.1? In that case it is 0.25*29.1=7.28 or roughly 7KVAR. On applying a further 85% reduction on it gives 7*0.85=6KVAR which is the size of the capacitor to be used.

The size of the actual capacitor used may be calculated using the following data:

No nameplate yet. Written on the door by pump installer: FLA 39.5. Max amp 45.2. (Assuming SF amps)

My measurements today
Motor amps before PFC 39.9
With PFC 32.6.

Fluke 43B says PF of about 97 with cap, 78 without. Assuming I connected it correctly, it's been awhile.
 

Phil Corso

Senior Member
Gentlemen,

Part 2 Surface and Down-hole values based on using nominally-rated parameters, including the motor-design listed in Part 1!


SURFACE VALUES
Vs, VoltsIs, AmpPFsSsPs, kWQs,kVAr
46036.10.833287.7239.6159.2
DOWN-HOLE VALUES
VmImPFmSmPm, kWQm,kVAr
45536.10.830284.6236.2158.7

Part 3, will cover the same situation, but using off-nominal parameters.

Part 4, will be based on PtonSparky's pre-PFC data, but using off-nominal parameters!

Part 5, will be based on PtonSparky's pst-PFC data, but using off-nominal parameters.

Phil
 

Phil Corso

Senior Member
Gentlemen...

Thank you for your patience. Following is Part 3 of the series! Please note using the original V, I, PF values in PtonSpark'y data, resulted in kVA, kW, & kVAr values different than the measured ones! I used the former values, i.e., V, I, PF values! Also note this calculation is based on operation w/o PFC!

PART 3:


CALCULATED SURFACE VALUES
Vs Is PF kVA P, kW Q, kVAr
496.2 39.9 0.790 34.3 27.1 21.0

CALCULATED SUBMERSIBLE CABLE VALUES
Vc Ic PF kVA P, kW Q, kVAr
4.5 39.9 0.99 0.42 0.42 0.05

CALCULATED DOWN-HOLE VALUES
Vd Id PFd kVA P, kW Q, kVAr
491.7 39.9 0.790 33.9 26.7 20.5

CALCULATED MOTOR VALUES
Vm Im Mtr Loss Pmech,kW Hp N, Rpm
491.7 39.9 1 kW 25.7 34.3 1,777

Phil Corso
 

Phil Corso

Senior Member
Finally, a conclusion...

As long as voltage remains the same, down-hole conditions are not at all affected by the PFC!!!

Why? The PFC is in parallel with the series circuit comprised of the down-hole cable and motor.

What, then, is affected? Just the supply current to the PFC location.

It can be proven quite easily by PtonSparky, when he is able! Simply measure three currents: 1) current from source; 2) current to down-hole feeder; and 3) current to PFC!

Also, because the off-nominal voltage is ~ 1.08 times higher than nominal, motor speed will, repeat, will, increase. It's rather easy to test. Just measure the motor's speed! And if you need help with "how", let me know!

PtonSparky... reur puzzlement over "imbalance factor":
The inductive-reactance of a flat-cable configuration is unbalanced because the distance between conductors is unsymmetrical. It is a serious problem for very deep for wells, resulting in motor failure. One cure is to "roll the cable" as is done in long distance transmission lines, yes, even long distance LV cables!

In some situations, when the cable can't be adequately rolled, a special device called a phase-equalizer is installed at the surface that controls phase-current imbalance, but that's a topic for another thread!

Regards, Phil Corso
 
Last edited:

Phil Corso

Senior Member
PtonSparky… regarding my original admonishment concerning over-correction of PFC…

Such a condition is highly unlikely to occur in your situation. Upon de-energization of the motor, check-valves will prevent water-column collapse, thus it can’t overhaul the motor!
Phil
 

ptonsparky

Senior Member
PtonSparky… regarding my original admonishment concerning over-correction of PFC…

Such a condition is highly unlikely to occur in your situation. Upon de-energization of the motor, check-valves will prevent water-column collapse, thus it can’t overhaul the motor!
Phil
Pump/well motor also has a ratchet that allows spin in only one direction No backspin when power is removed.
 

jjs

Member
thanks to all the participants. I enjoyed the thread.
one question, is down the hole measured at the motor at the point it sits in the well(hole) or does that mean something else?
 

ptonsparky

Senior Member
thanks to all the participants. I enjoyed the thread.
one question, is down the hole measured at the motor at the point it sits in the well(hole) or does that mean something else?
Calculated for that point if I understand it correctly.
 
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