Over correction

[Phil Corso]

Besoeker,

All that was necessary in my EXAMPLE to prove my point had been cited! Or have you confused my EXAMPLE with PtonSparky's case? Remember, it's solution is 10 months away, pending additional field-data!

Reur example...
1) What is the motor's FL-Rpm? Also, have you rounded it to the nearest multiple of 5?
2) Rated FL-Amps?
3) Is stator-winding Wye or Delta connected?

Phil

 

[Besoeker]

Besoeker,

All that was necessary in my EXAMPLE to prove my point had been cited! Or have you confused my EXAMPLE with PtonSparky's case? Remember, it's solution is 10 months away, pending additional field-data!

My data is from an existing machine and verified from string tests. It isn't 10 months away. It's actually three of the same design that are in current service in a pumping station.

Reur example...
1) What is the motor's FL-Rpm? Also, have you rounded it to the nearest multiple of 5?

I already provided that. It is 1493 rpm. No rounding whatsoever involved.

2) Rated FL-Amps?

It is 648A, a figure I also provided already.

3) Is stator-winding Wye or Delta connected?

Star.

I trust that I have answered your queries succinctly and look forward to your erudite response.

 

[Phil Corso]

Besoeker,

It's not my intent to evaluate or grade your methodology, but to use the info to make my point!

Phil

 

[Besoeker]

Besoeker,

It's not my intent to evaluate or grade your methodology, but to use the info to make my point!

Phil

Then do so.

 

[Phil Corso]

Besoeker...

Is Mech'l loss based on... per-phase or 3-phase?

Phil

 

[Besoeker]

Besoeker...

Is Mech'l loss based on... per-phase or 3-phase?

Phil

The figures are for the machine.

 

[Phil Corso]

Besoeker...

I give up... you snookered me! The machine is not the typical NEMA-based Induction-motor I expected (should have paid more attention to size)! Instead it's a very very special design, i.e., the FL slope is less than 1/2 of 1%, making the steep-slip-slope almost vertical.

I laud you for your the design!

Now, will you send me data for the more typical induction-motor having a slope of 3-5%?

Phil

 

[Besoeker]

Besoeker...

I give up... you snookered me! The machine is not the typical NEMA-based Induction-motor I expected (should have paid more attention to size)! Instead it's a very very special design, i.e., the FL slope is less than 1/2 of 1%, making the steep-slip-slope almost vertical.

I laud you for your the design!

Now, will you send me data for the more typical induction-motor having a slope of 3-5%?

Phil

The motors are not my design. I work with what i'm given.
I have now provided you with two real life examples. Real life proven data.
So, what data do you have to offer?

 

[Phil Corso]

Besoeker,

Reur "... mechanical design was someone else's responsibility." Your seemingly obdurate persona might be the reason you don't
understand the altered-voltage response or the Affinity Law!

Perhaps you should get more involved with mechanical folk!

Regards, Phil

 

[mivey]

Besoeker...

I give up... you snookered me! The machine is not the typical NEMA-based Induction-motor I expected (should have paid more attention to size)! Instead it's a very very special design, i.e., the FL slope is less than 1/2 of 1%, making the steep-slip-slope almost vertical.

I laud you for your the design!

Now, will you send me data for the more typical induction-motor having a slope of 3-5%?

Phil

In the interest of moving along your example:
150 Hp, 3ph, 460 V, 1800 rpm_synch, 1770 rpm_rated, 60 Hz

R1 0.0315
X1 0.0526
R2 0.0237
X2 0.0789
Xm 24.1894
Rm 138.8820
K 3,047

 

[Besoeker]

Besoeker,

Reur "... mechanical design was someone else's responsibility." Your seemingly obdurate persona might be the reason you don't
understand the altered-voltage response or the Affinity Law!

The altered voltage changes nothing.
More load torque, more slip, more power.

 

[Besoeker]

In the interest of moving along your example:
150 Hp, 3ph, 460 V, 1800 rpm_synch, 1770 rpm_rated, 60 Hz

R1 0.0315
X1 0.0526
R2 0.0237
X2 0.0789
Xm 24.1894
Rm 138.8820
K 3,047

Not sure where you got your figures from.
I normally use efficiency and power factor at 2/4, 3/4. and 4/4 load points to model the motor and generate values for the Steinmetz equivalent circuit.
Excel with a solver routine is how I go about this.
My main objective in doing this is to get a motor model that I can apply to VSD operation and predict performance.

 

[mivey]

Not sure where you got your figures from.

Just some estimated sample data for a completely different motor so Phil can show whatever it is he wants to show.

 

[Besoeker]

Just some estimated sample data for a completely different motor so Phil can show whatever it is he wants to show.

That's fine. I have motors from 7kW to over 6,000kW.
But let's wait to see what Phil wants.

I would reiterate a point I've made before.
We have had to guarantee performance figures at the bid stage of a project. That puts you between a rock and a hard place.
Bid too low an efficiency and lose the job to a competitor who bids just half a percent higher efficiency - yes those are the sort of margins.
Bid too high then failing to meet the claimed figures results in being clobbered with stringent penalties.
That's why I have gone for such a sophisticated model.
And it works.

 

[Sahib]

The altered voltage changes nothing.

Wrong. The torque of an induction motor is proportional to the square of the applied voltage. So Phil's thesis of increased KW of motor due to PFC depends on the latter ability to improve the voltage across the motor terminals.

 

[topgone]

Wrong. The torque of an induction motor is proportional to the square of the applied voltage. So Phil's thesis of increased KW of motor due to PFC depends on the latter ability to improve the voltage across the motor terminals.

What magnitude of voltage corrections are you talking about? Can you post some figures or calculations perhaps?

BTW, that affinity laws assume that there are no other automatic flow control schemes.

 

[Sahib]

What magnitude of voltage corrections are you talking about?

The voltage drop caused by lagging reactive current component of the motor load current in the supply leads to the motor is compensated by the capacitor across the motor terminals and that much voltage improvement would happen to the motor terminal voltage.

 

[Besoeker]

Wrong. The torque of an induction motor is proportional to the square of the applied voltage.

Perhaps you should have read to whole thread and the particular point I was addressing.
More slip, more torque, more power.
That simple relationship is still valid even if you raise the voltage.

In fact, torque/slip is quite close to a linear relationship for the motor I modeled.

 

[Sahib]

Perhaps you should have read to whole thread and the particular point I was addressing.
More slip, more torque, more power.
That simple relationship is still valid even if you raise the voltage.

In fact, torque/slip is quite close to a linear relationship for the motor I modeled.

Perhaps you do not want to agree what Phil was trying to convey: more KW from an induction motor due to PFC capacitor across its terminals under favourable circumstances.

 

[Phil Corso]

@ Sahib... Thanks! At least you get it it.

@ Mivey... Thanks for the intent! But, the data you proposed doesn't come close to the values necessary explain PtonSparky's situation!

@ Topgone... Please be patient! I'm working on it!

@ Besoeker... I get your point about eff'y, competition, guarantee, etc, but ur sophisticated model doesn't explain PtonSparky's situation!