Identifying Source and Load AC Circuit

[Joethemechanic]

What is available in test equipment to do this. Is there anything that will clip on that is capable? Or do I have to open the circuit and install something. I have watt-hour meters that will tell me, but the circuit has to be de-energized and opened up to install them. Is there any method that is quick and easy?

BTW, these circuits may have leading or lagging power factor currents in them.

 

[ron]

Do you mean a circuit tracer?

http://www.grainger.com/Grainger/ci...power-testing/test-instruments/ecatalog/N-b91

 

[Joethemechanic]

Ron,

I'm not sure exactly what that will do.


Sometimes when dealing with electric motors, and regen (say a mechanical load overdriving a squirrel cage motor) source and load are not always clear. Just for example motors (or a group of motors) or even some motors in a group can go from being loads to sources.

Maybe I should put it this way, What can I use for testing an AC circuit to tell what direction the power is flowing?

An example would be, is this motor acting as a motor and consuming power, or is it acting as a generator and producing power? It's not always so clear.

 

[K8MHZ]

Ron,

I'm not sure exactly what that will do.


Sometimes when dealing with electric motors, and regen (say a mechanical load overdriving a squerril cage motor) source and load are not always clear. Just for example motors (or a group of motors) or even some motors in a group can go from being loads to sources.

Maybe I should put it this way, What can I use for testing an AC circuit to tell what direction the power is flowing?

An example would be is this motor acting as a motor and consuming power, or is it acting as a generator and producing power. It's not always so clear.

The PV industry relies on bi-directional watt hour meters for net metering, so the technology for having a single device able to determine direction of power flow certainly exists.

As for a field test instrument that would do the same thing, sorry, but I am no help there.

 

[ron]

I can't give you a model number but I know power meters and a CTs will show positive/negative power depending on which orientation it is placed on the conductor. Some simple ones will give you the absolute value, so it wouldn't have a flow indication, but many do not.

 

[gar]

120116-1648 EST

Joethemechanic:

What price range?

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[Joethemechanic]

120116-1648 EST

Joethemechanic:

What price range?

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Gar

I'm guessing they aren't cheap. I have no idea. It's just something I came across the need for a few months ago and I've had in the back of my mind. I hooked up a regular watthour meter and it told me what I wanted to know. I was just wondering if there is a better way. I've been looking to update my testing equipment a bit, so I thought I would ask.

Joe

 

[iwire]

Maybe I should put it this way, What can I use for testing an AC circuit to tell what direction the power is flowing?

http://www.gedigitalenergy.com/products/specs/s_miw.pdf

 

[Joethemechanic]

http://www.gedigitalenergy.com/products/specs/s_miw.pdf

If the generator is accelerated from thepower system rather than the prime
mover, the reverse power element may
be blocked from start for a selectable
period of time.

Yeah something like that I think, but that is for permant install isn't it?

I mean if I am near things, and I can open and close circuits from experience I typically can tell if something is a motor or if it's a generator. But most of what I am going by are the mechanical tell-tale signs, Sound, exhaust color, what the drive coupling is doing, or even if it slows down or speeds up when I open the circuit.

I just wondered if there was something new that might just involve CTs and probes, and maybe some recording capacity.

I'll have to read into this thing though.

 

[jim dungar]

I just wondered if there was something new that might just involve CTs and probes, and maybe some recording capacity.

Like the standard power quality 'meters' available from Fluke, Megger, and Dranetz?

 

[Joethemechanic]

Like the standard power quality 'meters' available from Fluke, Megger, and Dranetz?

Are they capable of reading watts and can they tell me the direction of power and not just current?

I have no idea, I have a Fluke that is about 10 years old. I hardly use it. Off the top of my head I couldn't even tell you what model it is. I use a Simpson 260 analog and an Ideal amp clamp day to day.

 

[__dan]

What is available in test equipment to do this. Is there anything that will clip on that is capable? Or do I have to open the circuit and install something. I have watt-hour meters that will tell me, but the circuit has to be de-energized and opened up to install them. Is there any method that is quick and easy?

BTW, these circuits may have leading or lagging power factor currents in them.

For an induction motor, a tachometer may be the quick and slick method. There's probably something available in an optical non contact device.

The induction motor as a generator will have to be operated above synchronous speed and have negative slip to generate power. I have no idea what this does to voltage output and VAR production / absorbtion. But if you know the synch speed is 1800 or 3600 rpm, operation below synch speed indicates positive slip and the motor is a load, operation above synch speed requires positive slip and the load is driving the motor which drives power into the bus.

A synchronous motor / generator is exactly that. It operates synchronized to the bus within its stability limit. A tach will show no variance. There is a rotor angle factor if the rotor field is lagging the stator field and being driven by the stator field or the rotor angle leads and is being driven into the stator field.

If you have the budget for it, you may want to look at one of those $10,000 Fluke data loggers. I don't know if it will show you what you want to see but, hey, if it's the man's money, spending it is what keeps the economy going and people employed.

 

[Joethemechanic]

If you have the budget for it, you may want to look at one of those $10,000 Fluke data loggers. I don't know if it will show you what you want to see but, hey, if it's the man's money, spending it is what keeps the economy going and people employed.

The problem with it being "the man's money" is I'm the guy signing the checks. Even when I was employed by someone else, I was in a position where whatever I spent had to show a return. I was in a level of management where budget and staying within it were part of the job. I had a very tough mentor way back in the day. He died in 1987 and I still hear him every time I go to do something stupid. I can't even begin to tell you how he would have flipped if I spent 5 figures on a piece of equipment that I couldn't justify. He would have been at my house on Sunday morning just to chew me out.

I can measure what I want with a watt-hour meter, the two or three times a year that I need it would never justify the 10 G

 

[gar]

120116-2004 EST

Joethemechanic:

See https://www.ohiosemitronics.com/pdf/catalog/ac_watt_transducer_modelPC5.pdf
This is quite a capable device. I don't know the price.

I believe that fundamentally the internal components of a Kill-A-Watt could do what you want. But I do not believe they bring out the sign, but I suspect it is available from whatever chip is internally used. This is a $30 device to which accessories would be needed.

The TED 1000 MTU, uses a Cirrus chip, could do what you want with added accessories, and modifications to obtain the sign. Its cost is under $165.

Simpson has some digital panel meters for about $500.

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