Power factor correction experiment

[Besoeker]

Let's keep it civil guys.

Apologies. Please feel free to delete my last post if you feel it inappropriate.

 

[mivey]

Apologies. Please feel free to delete my last post if you feel it inappropriate.

I would must rather see that method used than just locking threads and punishing everybody.

A scalpel seems better than a machete and I think removing offensive parts of posts or even the whole post would do a better job at behavior modification.

 

[Besoeker]

I would must rather see that method used than just locking threads and punishing everybody.

A scalpel seems better than a machete and I think removing offensive parts of posts or even the whole post would do a better job at behavior modification.

Agreed. I have also suggested that here.

I'm a moderator on a couple of other forums. It can be a thankless task at times. Unsolicited and unfounded abuse on occasion.
If it's directed at me, I take no action on the basis that it would likely construed as abuse of my status. I'm a mellow fellow.

Anyway, my obfuscation comment was intended as a bit of levity. It probably should have had a smiley but then we Brits tend to like dead-pan humour.
Dave Allen, Irish, was a master at it and very popular on British television. Laid back, rueful......Jack Dee has a similar style...
Some my posts were a little in that sort of style but largely fell flat. The reference to Hamlet, this on Steinmetz....

I find it jolly useful and pretty reliable. Had it not proved so, I'd have been up to my balls in litigation claims.

Anyway, I have enjoyed posting in this thread. It has been challenging at times and many here have been immensely supportive.
And I greatly appreciate that.

I don't know where this thread will go now, if anywhere. It seems that the only dissenting voice has gone AWOL.
We don't know why, of course. I do hope that nothing untoward has affected him.
I request that the mods leave the thread open so that TM has a chance to respond and let us know that he is OK.

 

[mivey]

Besoeker,

The best I can surmise is that T.M. is just talking about a different kind of motor that does work with voltage control. Not sure why he went down that path.

 

[T.M.Haja Sahib]

I do hope that nothing untoward has affected him.
I request that the mods leave the thread open so that TM has a chance to respond and let us know that he is OK.

You are an infinitely kind person or it so appears to me.

 

[T.M.Haja Sahib]

I thought that you had already got there in post#199

I am not able to find any meaning in the above.:happysad:

You realise that this is for a wound rotor machine with an external rotor resistor, don't you?
I already addressed this point in post #177.

I asserted that the speed of an induction motor can be varied greatly with reduction in supply voltage.Your wordings in subsequent posts suggested as if it is impossible in principle.

I hope you agree with me now.Don't you?

 

[T.M.Haja Sahib]

"What we've got here is a failure to communicate."

Or, more accurately, a failure to understand scientific method. In the usual progression, someone presents their thesis, data, experiment information, and conclusion. IMHO, Gar (and Besoeker) have done this. The next step is for others to discuss the errors of fact or conclusion with their supporting data and conclusions. That essential part seems to be missing, without that it's "proof by blatant assertion". The main (only?) person arguing against Gar and Besoeker's statements seems to be T.M.Haja Sahib, however I don't think I've see him post any relevant data to support the statements made.

Mr Haja Sahib (I hope that is the correct form, my apology if it isn't), please present us with your own data from an experiment similar to that in post #1, or possibly a SPICE model (will etap do this?) for the proposed circuit. That will greatly help the discussion. Please do not direct me to other message without sufficient direction to pull out the relevant points. (If I had a sufficiently accurate power analyzer at hand this week, I'd do a similar experiment myself and present that data.)

Otherwise, we've already discussed a couple of salient matters- measurement accuracy and whether the device will result in a meaningful reduction in power consumption. Everything else, while interesting, is down a rabbit hole.

Sorry,but you did not notice that I only asserted that there may be energy saving due to PFC capacitor in a residence.A suitable thesis to support it is being established in the conversations in the forum.I put forward one thesis:a reduction in motor current with increase in voltage or vice versa.A capacitor can bring about increase in voltage but it is not yet clear if that will reduce the motor current.

 

[mivey]

I asserted that the speed of an induction motor can be varied greatly with reduction in supply voltage.

But we must also consider where that is practical. We might normally expect this reduction in voltage to cause a substantial increase in heating (for normal motors with running slips in the range of a few percent). So while we could reduce the voltage, we would also burn up our motor. Not a practical application.

If we start with a motor that has a high running slip, and build the rotor such that it can handle the increased heat from the increased current, now we can reduce the voltage over a respectible range and not burn up the motor. The problem is, we have to start out with a motor that is not very efficient to begin with and only gets worse as we lower the voltage. Still not what we seek.

 

[Besoeker]

I am not able to find any meaning in the above.:happysad:

Perhaps I was mistaken then. You sussed that the reduced voltage put the (quite improbable motor) into the unstable region - kudos to you for seeing that.
But it can't work there and, even if it could, currents would be excessive.

I asserted that the speed of an induction motor can be varied greatly with reduction in supply voltage.

By all means assert away. It's still not correct. Control of just the the supply voltage to the motor as a means of speed adjustment just won't hack it.

Your wordings in subsequent posts suggested as if it is impossible in principle.

Really?
The information I gave is based on practical examples and decades of experience. It's about what actually happens in practice.

I hope you agree with me now.Don't you?

Obviously not, given the above.

 

[Besoeker]

But we must also consider where that is practical. We might normally expect this reduction in voltage to cause a substantial increase in heating (for normal motors with running slips in the range of a few percent). So while we could reduce the voltage, we would also burn up our motor. Not a practical application.

If we start with a motor that has a high running slip, and build the rotor such that it can handle the increased heat from the increased current,

You need to beef up the stator as well. The increased current in the rotor winding is reflected back into the stator winding in much the same way as secondary current reflects back into the primary on a transformer.

 

[Besoeker]

You are an infinitely kind person or it so appears to me.

Thank you for that.

 

[gar]

111203-1105 EST

I have now run some bench tests on both the TED 1000 anfd 5000 Systems. Both TED Systems have a very serious problem with reactive loads.

Whereas the Kill-A-Watt does a good job on reactive loads, especially considering its price.

The TED power measurements on non-resistive loads are basically worthless.

Some results are:

[FONT=Courier New]
Voltage  Capacitance  Input Current  Input Watts   Input VoltAmp    Power Factor

No load:
117.0         0            -               1.4          -              -                 Kill-A-Watt
              0            -               0            -              -                 TED 1000

Motor only
117.0         0            -             140            -              -                 Kill-A-Watt
              0            -             172            -              -                 TED 1000

Motor + 70 ufd PFC
117.0        70            -             141            -              -                 Kill-A-Watt
             70            -             151            -              -                 TED 1000

70 ufd PFC only
117.0        70            -               4.5          -              -                 Kill-A-Watt
             70            -             220            -              -                 TED 1000


No load:
117.0         0            0.04            4              5            0.79              Kill-A-Watt
116.3         0            -               0             14            -                 TED 5000

Motor only
117.0         0            4.69          145            547            0.26              Kill-A-Watt
116.3         0            -             186            546            0.34              TED 5000

Motor + 70 ufd PFC
117.0        70            1.96          142            227            0.62              Kill-A-Watt
116.3        70            -             152            226            0.67              TED 5000

70 ufd PFC only
117.0        70            3.10            6.3          361            0.01              Kill-A-Watt
116.3        70            -             298            360            0.83              TED 5000

[/FONT]

 

[Besoeker]

111203-1105 EST

I have now run some bench tests on both the TED 1000 anfd 5000 Systems. Both TED Systems have a very serious problem with reactive loads.

Whereas the Kill-A-Watt does a good job on reactive loads, especially considering its price.

The TED power measurements on non-resistive loads are basically worthless.

Gar

How are you measuring input power?
Is it independent of the devices you are testing?

 

[mivey]

Gar:

Why the different Kill-A-Watt readings for the same condition? Or am I mis-interpreting the data?

 

[gar]

111203-1358 EST


Besoeker:

As my reference standards I am using a Fluke 27 (average reading), Flike 87 (RMS reading), Beckman 4410 (RMS reading), General Radio 1650-A bridge, and Ohmite resistors, incandescent bulbs, other resistive heating elements, and low dissipation capacitors. From these I can determine that the Kill-A-Watt meter is relatively good. The Kill-A-Watt is RMS (I do not know what the internal circuit is, but probably is similar to the Circus used in the TED System). Doing various tests with various loads the Kill-A-Watt does well on resistive loads, pretty good on partially reactive loads, and sufficiently well on a purely capacitive load. The Kill-A-Watt measures voltage, amperes, power, volt-amperes, frequency, and power factor.

What does relatively good mean? It means from low power of a few watts up to a maximum power of about 15*120 = 1800 W and widely varying power factor that a normal residential customer could measure loads in their home and not be grossly mislead in how changes in their loads would affect their energy consumption.

If you look at my data for measurements on the test induction motor that the Kill-W-Watt ranged from about 138 W to about 145 W under some severe changes in power factor correction capacitance. Also including different days the experiment was run and thus some variation in ambient temperature. Sometimes the only load on the Kill-A-Watt was the motor, and/or capacitor of various sizes. When comparing with the TED systems the TED System was an additional load, although small, on the Kill-A-Watt.

Using 138 W for the resistive component of the motor and 117 V I get a resistive current of about 1.180 A. The total current is about 4.66 A. Thus the reactive current is about 4.51 A.

When I put the 70 ufd capacitor across about 240 V, then its current is about 240/37.9 = 6.33 A and this overcompensates to create about 6.33 - 4.51 = 1.82 A of net capacitive current to the meter.

At 117 V the 70 ufd capacitor has a reactance of about 37.89 ohms and a current of about 3.088 A leaving a net inductive reactive current of 1.42 A. The Kill-A-Watt power reading, without and with the power factor correction capacitor, changed from 140 to 141 W, but the TED 1000 changed from 171 to 152 W.


mivey:

Does this also answer your question?

.

 

[mivey]

111203-1358 EST
mivey:

Does this also answer your question?
.

I was wondering why when you ran the scenarios with the TED1000 did the Kill-A-Watt have only watt readings but had additional data when running the same scenarios with the TED5000.

I think it seems clear that the TED is not a good device to use to evaluate the snake oil device. They are not made by the same parent company are they?

 

[Besoeker]

111203-1358 EST


Besoeker:

As my reference standards I am using a Fluke 27 (average reading), Flike 87 (RMS reading), Beckman 4410 (RMS reading), General Radio 1650-A bridge, and Ohmite resistors, incandescent bulbs, other resistive heating elements, and low dissipation capacitors. From these I can determine that the Kill-A-Watt meter is relatively good. The Kill-A-Watt is RMS (I do not know what the internal circuit is, but probably is similar to the Circus used in the TED System). Doing various tests with various loads the Kill-A-Watt does well on resistive loads, pretty good on partially reactive loads, and sufficiently well on a purely capacitive load. measures voltage, amperes, power, volt-amperes, frequency, and power factor.

I don't doubt that the the Kill-A-Watt measures all of that.
But I'd like to know more about your basis for independent power measurement.
Or more significantly, energy measurement.
I used our domestic energy meter as the final arbiter.
That's what determines your energy bill.

 

[gar]

111203-1916 EST

mivey:

I have two TED 1000 Systems. I only have one Footprints software package to collect data from the 1000. That software is uniquely linked to the 1000 System I have monitoring my house power. The display only portion of the TED 1000 System only provides readout of power or something else. I could have shut down house monitoring and used that hardware to run the test. I was really only interested in how the TED 1000 power measurement varied with a change of power factor because if it was poor, then that was an explanation for why my prior attempt to evaluate the PFC on the whole house failed. I also did not bother to make the other measurements with the Kill-A-Watt because I have done those enough to know that there is little variation.

The TED 5000 System has a somewhat different system design and I could get other data at each data point without great difficulty. Thus, more complete information. The test with the 5000 was to see if the power factor problem had been corrected. It has not. In many respects from my point of view the 5000 System is a newer, but more poorly developed system. At the moment, and maybe never, I am not interested in trying to find out why the TED products have a power factor problem.

I am quite critical of some aspects of the TED Systems, but for a low cost system they can provide a homeowner some very useful information. They just can not be used to prove to a customer or anyone else that PFC capacitors won't save the homeowner any money.

TED and Kill-A-Watt are two different companies. TED is geared to whole house monitoring. Kill-A-Watt is a 120 V 15A max device for measuring cord connected devices.

.

 

[gar]

111203-1939 EST

Besoeker:

I can measure resistance, voltage, and current relatively accurately for my purposes.

This I have done and over the measurement range of the Kill-A-Watt I have determined that it is reasonably accurate. Then I have used low D capacitors to show that the Kill-A-Watt reads near 0 watts with the capacitors as the only load. Note: how bad the TED performance is when subjected to a nearly pure 90 deg shift in the current.

For intermediate PFs my motor test shows stability of the resistive component as the PF is changed. This is a fairly good test that the Kill-A-Watt is fairly accurately handling changing power factor.

An instantaneous power measurement on the whole house for proof that PFC won't save any energy is much easier, than trying to use the utility kWh meter to accomplish the same objective. But I am going to have to follow that route with my outside meter if I can not get a kWh meter from the utility. Currently we have wind, rain, snow, cold as obstructions to using the outside meter. My plan is to set a video camera in front of the meter to get accurate timing information of disk rotation, simultaneously do the TED whole house monitoring, and cycle the PFC on and off over maybe 5 to 10 minute periods. This time is partly controlled by the furnace blower on-off period. Blower on time is about 11 minutes. Refrigeration equipment has long time constants, and there are three of those, and some miscellaneous other items that cycle on and off. So to get a clean steady load may take a while, especially during the day.

This is clearly not something I can tell an average consumer to do and expect much success.

If we take a long time average of the kWh, one month, then measurements tend to stabilize. But my daily averages for the following date periods were:

42.80 kWh 6-28-11 thru 8-14-11
38.48 kWh 8-15-11 thru 9-14-11
36.02 kWh 9-15-11 thru 10-14-11
42.35 kWh 10-15-11 thru 11-5-11

Month to month this is not sufficiently consistent to use to prove anything about PFC. Midnight to 7 AM is more consistent from one day to the next but more difficult to get the measurements from the utility kHr meter.

.

 

[T.M.Haja Sahib]

But we must also consider where that is practical. We might normally expect this reduction in voltage to cause a substantial increase in heating (for normal motors with running slips in the range of a few percent). So while we could reduce the voltage, we would also burn up our motor. Not a practical application.

I am afraid you did not read post #244.The current taken by the example induction motor with full load current of 18A driving a fan type load does not exceed 7A at 0.55 p.u voltage.

If we start with a motor that has a high running slip, and build the rotor such that it can handle the increased heat from the increased current, now we can reduce the voltage over a respectible range and not burn up the motor. The problem is, we have to start out with a motor that is not very efficient to begin with and only gets worse as we lower the voltage. Still not what we seek.

The increase in rotor resistance was meant to drive the rated load at much reduced speed.But here we are discussing about fan type load whose torque requirement is much less at reduced speed.So your objection does not seem relevant.