EMI Filter understanding

[lilimike]

I can not understand what is happening here. I have this unit

Based on this picture:

I plug in a motor which is pulling 6 Amps in plug A, I plug in the EMI filter (link from above) in plug B.

When my plugs are connected like in #1, EMI filter drops the the Amps down to 3
When my plugs are connected like in #2, EMI filter has no affect.

For both #1 and #2 plugs are 6 inches apart and wires are 18 inches long.

I am clueless!

Mike

 

[Pommie]

The sockets should be wired as in B. The device you have bought appears to be another con. It correct the power factor and so will reduce the current into your house. It will not however reduce your power bill as you only pay for power that is used. Sorry.

Wow, just noticed the price, $200, what a con.

Mike.

 

[lilimike]

Hi Mike,
Although I just Googled for "Power Factor" I still don't quite understand...
If I connect it as in #1 I can observe the current dropping by 50% so if I have the same voltage and the current drops by 50% am I not consuming 50% less power?

Mike

 

[Pommie]

If you wire items in series they will get half the voltage each and consume less power and do less work. Wire a fridge like that and you may damage the motor. When wired in parallel, as they should be, it will make no difference. All that unit contains is a $2 capacitor. It's a con. Sorry.

Mike.

 

[RCinFLA]

You been had.

First, in order to have motor current drop by 50% the motor must be almost unloaded. Second, as already stated you don't pay for appearent power. You pay for true power. If you plug in an inductor of 53 mH you will draw 6 amps from 120 vac 60 Hz line. You will consume almost no true power. (there is some wire resistance loss in a real inductor that results in some real power loss)

It is because of the phase relationship between voltage and current. True power is V * I * cosine of phase angle between voltage and current. For a pure inductor the voltage phase leads current phase by 90 degrees. cos (90) = 0, therefore no power is consumed. Energy stored in inductor during part of sinewave is returned during other part of sinewave.

A commercial power customer, like a large power consuming factory, does get charged if their power factor is poor. The commercial customer must take action on PF corrections or they get charged a penalty by power company.

 

[lilimike]

Sorry my drawing is not very clear, both #1 and #2 are connected in parallel, each set of screws on the plugs have not been separated and that is why I don't understand what is happening. Look at this video (you can skip to 3:14) I get the same results but I can't explain why and on top of that, I get different results based on how I connect.

Mike

 

[RadioRon]

Assuming that the link tabs on each side of the socket in picture #1 have not been broken off, then electrically there is no difference between 1 and 2 and I can't see why you would be seeing a difference in motor current consumption. However, Pommie is correct that the wiring should be as in #2 for safety reasons, code compliance, and to follow industry standards (which is important in house wiring).

As for this device you are using, it will not save you any money. One big reason is that residential power factor correction has no affect on your bill because your electric meter is measuring true power consumed, which remains the same regardless of power factor.
More info:
**broken link removed**

 

[lilimike]

Assuming that the link tabs on each side of the socket in picture #1 have not been broken off, then electrically there is no difference between 1 and 2 and I can't see why you would be seeing a difference in motor current consumption. However, Pommie is correct that the wiring should be as in #2 for safety reasons

Yes I am aware of this, I have worked as an electrician in my early days and I understand very well that there should be no difference in the current between connecting like #1 and #2 but???

And for the difference in current, thank you RC and Ron, I will look more in details about what you are saying on true power.

But I still see a mystery with a difference between #1 and #2!

Mike

 

[RadioRon]

Yes, it is a bit mysterious. Since you have worked with electricity, there is no point in asking my next question which is where did you measure motor current? I will assume you measured motor current by putting a clamp meter somewhere along the motor supply cable, on the motor side of the outlet. That's the way I would do it, even though it makes it difficult to put the clamp on. I will also assume that the clamp meter measures true RMS current. Can you confirm?

 

[lilimike]

I am using a shunt resistor with a panel mount type ammeter near the AC supply and I double checked with a clamp-on ammeter that comes with an inline inductive coil. Both units don't have enough specs to know if they are measuring true RMS.
Clamp-on is an old analog meter and although not precise I got pretty much the same readings on both.

Panel mount ammeter
Clamp-on ammeter

Mike

 

[RadioRon]

After some thought, I decided to approach this like Sherlock Holmes. Principles of electricity tell me that there should be no difference in your current reading whether plugs are wired as in #1 or #2, so I deduce that the plugs are not wired as in #1 or #2.

 

[lilimike]

ok so let me give you the complete story. I didn't buy the EMI filter, I borrowed it to make some tests because I was skeptical about this unit so I built a small test box by wiring a voltmeter, ammeter and its shunt as indicated in the previous links, a regular home wall switch and 2 plugs and I connected the plugs as in my drawing (#2) I had the AC supply feeding the switch and then the shunt and then a small power supply I made to provide 12 volts to voltmeter and ammeter.
From the above configuration I plugged the EMI filter in plug B and a motor in plug A, turned on the switch, motor came on, ammeter showed 6A, turned on EMI filter and nothing changed, still reading 6A. (double checked with my clamp-on meeter to confirm) and made sure I have 120V in plug B.

I then connected the wires like in #1, did the same test and when I turned on EMI filter the ammeter dropped to 3A.

Surprised overwhelmed and confused I decided to make another test.

I plugged-in the EMI filter in the bottom outlet of my garage plug and the motor on the top outlet (both on same plug) along with my clamp-on inductive coil and turning EMI filter on in this configuration made no change in Amp reading which was at 6A.

At that point I figured my garage plug was separated in 2 breakers so I plugged in a power bar on that plug and did the same test this time plugging the EMI filter and the motor on the power bar and it turned out the EMI filter reduced from 6A to 3A when turned on.

I then gave back the EMI filter to its owner and I was still confused... I opened my garage plug to find both outlets are on the same breaker.

I have been getting headaches and migraines since and I am glad to see Sherlock Holmes in my path.

I will definitely redo my tests and I will either film or take pictures because its not making sens and I believe to still have all my head, I am only 50!

I now understand better the power factor issue but why the difference between #1 and #2 as well as on the plug and on the power bar?

Maybe the EMI filter is defective with a loose contact and only works sometimes?

If not, it is still a mystery.

Does my story help clarifying anything?

Mike

 

[RadioRon]

Well, your story seems to remove all the unknowns, and yet it still doesn't make sense. Wired in parallel is wired in parallel, and either way appears to be wired in parallel to me. I give up.

 

[lilimike]

Gee you give up easily!
For now I will stick to the possibility that the filter was defective but I will test again for sure.

Mike

 

[RadioRon]

I wouldn't let it go so easily if I was there in the same room as the equipment. But from over here on the west coast, I feel kinda helpless.