Power factor / efficency of shaded pole motors

[wwhitney]

So just a little basic trig, if I subtract the true power (watts) sqrd from apparent power (va) sqrd = sqr rt looks like 694.48 VARs inductive. Yes?
Correct?

True for endpoint (2) of the post of mine you quoted.

Let me observe that the numbers in that post were based on a presumed mechanical output of 190W. Subsequent posts from the OP suggest that the actual mechanical output in the OP's situation is lower, 100W-150W. The discrepancy is from my interpreting the OP's statement that the motor "should" draw 1.6A as meaning that a 100% efficient motor with power factor 1 would draw 1.6A in his application, while he meant his replacement motor (not a shaded pole motor) is rated to draw 1.6A.

Cheers, Wayne

 

[mbrooke]

True for endpoint (2) of the post of mine you quoted.

Let me observe that the numbers in that post were based on a presumed mechanical output of 190W. Subsequent posts from the OP suggest that the actual mechanical output in the OP's situation is lower, 100W-150W. The discrepancy is from my interpreting the OP's statement that the motor "should" draw 1.6A as meaning that a 100% efficient motor with power factor 1 would draw 1.6A in his application, while he meant his replacement motor (not a shaded pole motor) is rated to draw 1.6A.

Cheers, Wayne

I apologies for the confusion, as I do not know the EXACT shaft power required, but it is somewhere in the 100s, hence why I am throwing out loose values.

 

[mbrooke]

What do you mean by "Fast"? An 8-pole version, Ns=900rpm, as well as a reversible-version were also available.

Phil

IF a shaded pole motor changes magnetic field more than an induction motor, does that mean it spins faster?

 

[mbrooke]

True for endpoint (2) of the post of mine you quoted.

Let me observe that the numbers in that post were based on a presumed mechanical output of 190W. Subsequent posts from the OP suggest that the actual mechanical output in the OP's situation is lower, 100W-150W. The discrepancy is from my interpreting the OP's statement that the motor "should" draw 1.6A as meaning that a 100% efficient motor with power factor 1 would draw 1.6A in his application, while he meant his replacement motor (not a shaded pole motor) is rated to draw 1.6A.

Cheers, Wayne

Here is a pic of the new motor's sticker:

 

[mbrooke]

True for endpoint (2) of the post of mine you quoted.

Let me observe that the numbers in that post were based on a presumed mechanical output of 190W. Subsequent posts from the OP suggest that the actual mechanical output in the OP's situation is lower, 100W-150W. The discrepancy is from my interpreting the OP's statement that the motor "should" draw 1.6A as meaning that a 100% efficient motor with power factor 1 would draw 1.6A in his application, while he meant his replacement motor (not a shaded pole motor) is rated to draw 1.6A.

Cheers, Wayne

And the old motor, rated 5.5 amps at 120 volts:

 

[Phil Corso]

IF a shaded pole motor changes magnetic field more than an induction motor, does that mean it spins faster?

Certainly not!

Phil

 

[ActionDave]

And the old motor, rated 5.5 amps at 120 volts:

That motor is a whole lot older than the pump it is hooked up to. What is the deal?

 

[Sahib]

IF a shaded pole motor changes magnetic field more than an induction motor, does that mean it spins faster?

Better question IMO: Is formula N=F/P, slip etc., applicable for shaded pole motor?

 

[Phil Corso]

Better question IMO: Is formula N=F/P, slip etc., applicable for shaded pole motor?

No! Ns = 120xF/P at rated V, Then Nr = (1-slip) x Ns, with slip given as decimal!

Phil

 

[mbrooke]

That motor is a whole lot older than the pump it is hooked up to. What is the deal?

GE was stuck in the past :lol: That exact motor was actually first introduced in the late 1960s, built around 50s design, but it was used up until 2002 even though every single other part around it changed many times over :blink:


Don't believe me? Here are used pumps from the 90s:



http://www.tcapplianceparts.com/product/ge-dishwasher-motor-pump-pn-wd26x10013-wd26x81-wd18x213

http://www.american-appliance.com/old_Site/images/image_data/gedwpump58796321.jpg

80s version:

http://www.terapeak.com/worth/ge-di...aced-by-wd26x0081-or-wd26x10013/111805844727/


The new version will directly retrofit pumps from the 70s:

This pump and motor kit replaces many old style pump and motor kits that were manufactured since 1970. The instructions are included with this kit to help you to make it adaptable to your dishwasher. NOTE: This is a completely redesigned kit by the manufacturer and now includes the drain solenoid.

http://www.partselect.com/PS260801-GE-WD26X10013-Motor-and-Pump-Kit.htm



When GE ditched the motor:

 

[kwired]

GE was stuck in the past :lol: That exact motor was actually first introduced in the late 1960s, built around 50s design, but it was used up until 2002 even though every single other part around it changed many times over :blink:


Don't believe me? Here are used pumps from the 90s:



http://www.tcapplianceparts.com/product/ge-dishwasher-motor-pump-pn-wd26x10013-wd26x81-wd18x213

http://www.american-appliance.com/old_Site/images/image_data/gedwpump58796321.jpg

80s version:

http://www.terapeak.com/worth/ge-di...aced-by-wd26x0081-or-wd26x10013/111805844727/


The new version will directly retrofit pumps from the 70s:





http://www.partselect.com/PS260801-GE-WD26X10013-Motor-and-Pump-Kit.htm



When GE ditched the motor:

GE is blowing smoke to those that don't understand, both motors are likely controlled by a "relay" of some sort. They likely switched from a shaded pole to a PSC motor, and it probably does run cooler under same load conditions.

 

[mbrooke]

GE is blowing smoke to those that don't understand, both motors are likely controlled by a "relay" of some sort. They likely switched from a shaded pole to a PSC motor, and it probably does run cooler under same load conditions.

They are blowing and that explanation sucks to be honest. That and the replacement does not come with the boots they brag about. But they are still correct about the shaded pole motor being used up until 2001. The new motor is indeed cooler and a heck of a lot quieter, not to mention current draw went down by about 4 amps.

 

[mbrooke]

But anyways, if the PF is say 50%, am I correct to assume that the active power (waste heat plus work) is around 330 watts?

 

[wwhitney]

But anyways, if the PF is say 50%, am I correct to assume that the active power (waste heat plus work) is around 330 watts?

If the "apparent power" V x A is 120V x 5.5A = 660VA, then by definition when the PF is 50%, the active power is 330W.

You were also correct that the "active current" (current through the resistor in a parallel RL model) is 2.75A. The only wrinkle is that the "reactive current" (current through the inductor in a parallel RL model) is not 2.75A, it is 4.76A as discussed earlier.

Cheers, Wayne

 

[mbrooke]

If the "apparent power" V x A is 120V x 5.5A = 660VA, then by definition when the PF is 50%, the active power is 330W.

You were also correct that the "active current" (current through the resistor in a parallel RL model) is 2.75A. The only wrinkle is that the "reactive current" (current through the inductor in a parallel RL model) is not 2.75A, it is 4.76A as discussed earlier.

Cheers, Wayne

That discrepancy is what through me off.

Now, the those 330 watts, assuming the motor is 20% efficient, would boil down to 66 watts of torque and 264 watts of heat?

 

[wwhitney]

That discrepancy is what through me off.

Yeah, when currents are in phase, then 2.75A + 2.75A = 5.5A.

But when currents are 90 degrees out of phase, 2.75A + 2.75A = 2.75 * sqrt(2). Or in your example, 2.75A + 4.76A = 5.5A.

Now, the those 330 watts, assuming the motor is 20% efficient, would boil down to 66 watts of torque and 264 watts of heat?

The numbers are correct, but I would say 66 watts of turning power (mechanical power) and 264 watts of heating (thermal power). Torque and heat have the wrong units.

Cheers, Wayne

 

[mbrooke]

Yeah, when currents are in phase, then 2.75A + 2.75A = 5.5A.

But when currents are 90 degrees out of phase, 2.75A + 2.75A = 2.75 * sqrt(2). Or in your example, 2.75A + 4.76A = 5.5A.

This formula works for all applications?

The numbers are correct, but I would say 66 watts of turning power (mechanical power) and 264 watts of heating (thermal power). Torque and heat have the wrong units.

Cheers, Wayne

I know. Technically its torque x speed, but I am over simplifying things in order to "get it" lol. Sorry about all the confusion. :ashamed1:

 

[wwhitney]

This formula works for all applications?

Vector addition of the phasors will work for multiple sinewaves of the same frequency.

For two sinewaves 90 degrees out of phase, this reduces to the "pythagorean theorem": |A+B| = sqrt(|A|² + |B|²).

Cheers, Wayne

 

[romex jockey]

Interesting thread....

As i'm currently working a lot of 'green' retrofit jobs where state agency efficiency officials target lighting , i wonder why these particular motors seem a secondary concern, being the obvious energy hogs ???

Perhaps they can't do the 'math' as this crew can?

~RJ~

 

[iwire]

Interesting thread....

As i'm currently working a lot of 'green' retrofit jobs where state agency efficiency officials target lighting , i wonder why these particular motors seem a secondary concern, being the obvious energy hogs ???

Perhaps they can't do the 'math' as this crew can?

~RJ~

I would think in most buildings there is much more lighting that is on more hours than the motors so they are going after the easy first.

On the other hand in each of the supermarkets I work for they have 100s of small fan motors that run 24/7. They did go around and swap out the motors for much higher efficiency motors.