Hi,

I am trying to calculate the power of a machine by measuring the currents and voltages of the machine using Fluke 434/435. The machine is connected to a three-phase power supply. The information plate of the machine tool says the following information:
- Voltage: 400
- Phase: 3
- Hertz: 50/60
- Full load: 13 Amps
- Largest Load: 21 Amps
- Machine Total Power: 5.6 kW

The recorded data that I am getting is around
- V1: 413 Volt, I1: 68.1 Amps
- V2: 416.9 Volt, I2: 68 Amps
- V3: 415.45 Volt, I3: 70.1 Amps
- Active Power 39360 W
- Reactive Power 4346.7 W
- Apparent Power: 39786.7 W
- Power Factor: 0.78
- Crest Factor (for V1 V2 V3): 1.42, 1.41 and 1.41 respectively.
- Crest Factor (for I1 I2 I3): 2.13, 2.09 and 2.04 respectively.

- How it comes the maximum current of the machine is 13 Amps but I am getting about 70 Amps in each phase?
- Why the apparent power is nearly equal to the active power and both of them are far away from the machine total power?!

Please note that I set up the Fluke to record from Delta 3-phase circuit, but I am not totally sure if the circuit is in Delta or Wye configuration. How can I make sure?!

I would like to let you know that I have a limited background in electrical stuff. So, please consider that in your answer.

Thank you.

 

Is there a neutral wire connection? A neutral wire would imply that it is Wye connected. ... No neutral wire ... then Delta connected.

 

There is a neutral wire connection.

 

In that case, the phase to neutral voltage would be about 400/1.73 =231 volts.
Is it possible to set the Fluke instrument to the Wye measurement configuration, in conjunction with the neutral terminal?

 

Do you have the Fluke datasheet? There is a Wye connection diagram ...

 

There is a lot of information not provided here, and without that information all that is delivered is best guesses. A "machine" could be anything at all, with any possible phase angle AND the "machine" could even be a power supply and the information plate could be for the output power. So a more detailed description of the power connection and just how the measurements connections are made would allow for a more accurate discussion about what is happening. None of us are standing near that machine and very few of us are good mind readers, I am certainly not one.
Is this Fluke device measuring current into the machine? And is it measuring voltage into the machine? OR, might this be a power converter and the specification is for the output? An accurate description of the connections may provide the explanation.

 

There could be a setting for the current clamp selection. Please check the current clamp used, and make the setting in the Analyzer to correspond to the current clamp used.

 

In that case, the phase to neutral voltage would be about 400/1.73 =231 volts.
Is it possible to set the Fluke instrument to the Wye measurement configuration, in conjunction with the neutral terminal?

Yes, I did that and I got similar Amps. The readings of each phase were as follows:
- V1: 240.3 Volts, I1: 69.8 Amps
- V2: 241.3 Volts, I2: 70.9 Amps
- V3: 242.4 Volts, I3: 72.1 Amps
- Active Power for L1 L2 L3 and N: 13240 W, 13760 W, 14080 W and 41080 W
- Reactive Power for L1 L2 L3 and N: 1760 W, 986.7 W, 1560 W and 4306 W
- Apparent Power for L1 L2 L3 and N: 13360 W, 13800 W, 14160 W and 41306 W
- Power Factor for L1 L2 L3 and N: 0.78, 0.79, 0.79 and 0.79
- Crest Factor (for V1 V2 V3 N): 1.42, 1.43, 1.43 and 327.7 respectively.
- Crest Factor (for I1 I2 I3 N): 2.15, 2.11, 2.05 and 327.7 respectively.

The readings above was recorded when I set up the Fluke on Wye connection diagram as shown below.

Do you have the Fluke datasheet? There is a Wye connection diagram ...

The datasheet only contains the parameters that I am measuring (Amps and Voltages for each phase, power, power factor, etc.). Choosing the connection diagram can be done in the set-up stage and before recording. But the question is how can I make sure is it the right configuration?

There is a lot of information not provided here, and without that information all that is delivered is best guesses. A "machine" could be anything at all, with any possible phase angle AND the "machine" could even be a power supply and the information plate could be for the output power. So a more detailed description of the power connection and just how the measurements connections are made would allow for a more accurate discussion about what is happening. None of us are standing near that machine and very few of us are good mind readers, I am certainly not one.
Is this Fluke device measuring current into the machine? And is it measuring voltage into the machine? OR, might this be a power converter and the specification is for the output? An accurate description of the connections may provide the explanation.

The machine is HAAS TL1 CNC Lathe Machine Tool and you can see the information plate below:

The clamps of the Fluke were connected to a power unit and this power unit is between the source and the machine tool as seen below:

The Fluke connections are located to the side of the power unit as shown below:

The Delta configuration that I used is

There could be a setting for the current clamp selection. Please check the current clamp used, and make the setting in the Analyzer to correspond to the current clamp used.

Do you mean there might be a switch on the clamp itself for the scaling ratio? (so the actual current reading is 6.61 amps instead of 66.1 amps)

 

Do you have a multimeter or a voltmeter that you can use to measure the voltage independently from the Fluke analyser?
Next question: The tag says that the overcurrent protection is at the input of the machine. Check the ratings of those and you will find that it is a lot less than 70 amps. Thus the error must be in the instrumentation. I have not seen clamp on current sensors mounted like that before, so I am wondering if there is some magnetic coupling that is causing the error.
In addition, the magnitudes of the discrepancies point toward the clamp-on devices being 30 amps full scale while the setting is thinking it is 400 amps full scale. Can you independently read the voltage outputs from the three clamp-on probes? Are they really wired correctly??

 

The Fluke datasheet states that scaling is available on the current scale.
Check the main menu or the setup button to see what it is.

Edit ... current clamp is 'switchable' somehow, so take a look to check if that means on/off or scalable. There should be a Startup manual ... might be something there.

 

Well it is patently obvious that the machine is not drawing that current, otherwise you would see obvious results and machine malfunction.
There are several Utube videos on correct setting up of the meter, one by a Fluke rep.

Max.

 

From what I can find, the standard flexible current clamps for that instrument have an output of about 85 mV [!] at 1000 A. From the photos, the probes n the box look like they probably aren't suitable for more than a couple hundred amps, if that, and probably have a different scale factor, requiring a different configuration for the instrument. The instrument manual shows no less than 11 different current clamps that can be selected in the instruments scaling menu.

 

Do you mean there might be a switch on the clamp itself for the scaling ratio? (so the actual current reading is 6.61 amps instead of 66.1 amps)

Yes.

The manual says current clamp is 400A, and 1mV/A or 10mV/A. I would imagine there should be a switch, just as you had mentioned too! There's likely to be a setting in the analyzer too.

PS : Please correct 10mV/A to 40A, 10mV/A.

 

Looking at the phots in post#8, the wire size looks like #12 or #14. Neither size would last long at 70 amps. AND, once again I suggest checking the over-current protection devices at the load. They will probably be 30 amps, at most. Then there is another possibility, since that whole box seems to be made for tapping in to read volts and amps. Possibly there is some flaw in the circuit that is inflating the current readings. Things like that do happen. Also, once again, I suggest reading the output voltage of those clamp-on devices with a different AC voltmeter. That would help find the location of the problem quite a lot. One more suggestion is to show a circuit of what all is in that box with the clamp on sensors. That might explain a whole lot, or not.

 

Yes.

The manual says current clamp is 400A, and 1mV/A or 10mV/A. I would imagine there should be a switch, just as you had mentioned too! There's likely to be a setting in the analyzer too.

For the claimed maximum current the only probe that makes sense is the 30 amp clamp-on. for the 400 amp one, 20 amps is only 5% of full scale, not a best choice. Thus there may be several errors in the system, not just one error.

 

I had a bit of browse of the Fluke site and couldn't find any probes that looked like those in the photos. Certainly none of those listed as accessories for that instrument look right, unless I missed one. Perhaps it is a discontinued model or some other manufacturer's product in Fluke-ish colors.

The machine is a CNC lathe with a 10 HP motor. The current doubtless varies substantially depending on what it is doing, and "full load" may be something rather difficult to accomplish, though the programming software may be good at keeping it hogging off metal as fast as possible most of the time. I wouldn't be terribly surprised if the current measurements reported are off by an order of magnitude.

 

For the claimed maximum current the only probe that makes sense is the 30 amp clamp-on. for the 400 amp one, 20 amps is only 5% of full scale, not a best choice. Thus there may be several errors in the system, not just one error.

My bad, I missed 40A. It should have been 400A 1mV/A, 40A 10mV/A.

 

Does the clamp say anything about the scaling? I just saw the config page photo of the analyzer posted.
I think it should be okay, if you change the current clamp in the config page to the one you are using. With 40A 10mV/A, the current figures should go down by a factor of 10.

Manual is available here - https://www.fluke.com/en-us/product/accessories/current-clamps/fluke-i400s#

 

Finally, the problem solved!

It was because of the clamp configuration on the Fluke was on the wrong scale. The current clamps were set to be on 10mV/A (40A) as seen from the picture below. So, the Fluke analyzer should be reading on the same scale as seen from the other two pictures. Exactly as RamaD described it.

The wrong settings on the Fluke:

The settings after correction:

This kind of basic mistakes can take some of your valuable time trying to understand what is going on, especially when you don't have a solid background in electrical stuff (just like me ).

Thank you all.