Open Delta and frequency

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mivey said:
Loose reference to quote from Marcellus to Horatio in Hamlet, IOW something is askew.
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Ha. Hamlet came immediately to mind.

Now, I was checking the definition of "askew" to see if it implied 3D, as I was picturing it. It doesn't, but Google played it well when I searched the word.
 
OK, I kind of got the answer I need from the non-answer. First let me state that I don't know if the actual system is open-delta or not. It was merely a possibility and given which phases read what, I could speculate that there may be a connection between a multimeter frequency reading and an open delta installation. So, with the expertise here, the lack of a definitive answer basically tells me there is not a direct correlation and if the customer wants us to pursue it, then other approaches will be necessary. The whole reason my journeyman even put the meter on is because the customer bought a piece of Chinese equipment that is 50hz and the customer wanted to see the frequency on a meter. As far as I know there is not any indication in the existing equipment of a frequency problem.

[edit] Thank you all for your responses.
 
High leg and open delta systems are pretty common here - now I have to check to see what I get on them.

Will be at a place supplied by high leg system today - but is a full delta supply on this one.
 
North America (USA, Canada, Mexico) are all 60 Hz. With a few exceptions (in primarily US based economies), everywhere else in the world is 50Hz. 50Hz equipment with AC motors will run 20% faster here. If the voltage design is 380-400V 50Hz, it will produce full torque at 480V 60Hz, just faster. If rated 230V50Hz however, powering it with 230V 60Hz will possibly saturate the windings and overheat the motors. Some better quality 230V motors will be labeled for 50/60Hz, but I would not count on that from a Chinese supplier.
 
Jraef said:
North America (USA, Canada, Mexico) are all 60 Hz. With a few exceptions (in primarily US based economies), everywhere else in the world is 50Hz. 50Hz equipment with AC motors will run 20% faster here. If the voltage design is 380-400V 50Hz, it will produce full torque at 480V 60Hz, just faster. If rated 230V50Hz however, powering it with 230V 60Hz will possibly saturate the windings and overheat the motors.
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At 230V 60Hz, it will be lower flux so saturating the windings is not an issue.
 
Jraef said:
Oh right. Usually I'm going the other way, people sending 60Hz motors to 50Hz countries.

So under fluxing results in less torque, more slip, often higher current draw.
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Yes, it may. The higher speed would be a concern for many applications.
 
171102-1256 EDT

I have 3 LED AC line driven clocks, at least 40 years old. Other than for having to be reset on loss of AC power they are the best from the standpoint of readability.

This morning I used a Fluke 87 to read frequency on a two transformer high leg 240 V delta. On 120 V read a solid stable 60.02 Hz in AC V autorange.

Then with same setup from high leg to EGC got inconsistent frequency readings. Jumped all over. Went to fixed AC range, then got a consistent 60 Hz reading.

I need to take the scope to the shop and see what the signal looks like. I have no idea what Fluke does to obtain their frequency measurement.

When using instruments to make measurements one needs some knowledge of how the instrument works to allow interpretation of unexpected results.

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Besoeker said:
Do you still have mains driven electric clocks? I haven't seen one in donkey's years.
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Yes, I have several of them. I also have a couple of reel to reel tape machines that have AC synchronous motors. One of them has a 50/60 Hz switch on the back but the other doesn't. I haven't used them in many years, though.
 
gar said:
171102-1256 EDT

I have 3 LED AC line driven clocks, at least 40 years old. Other than for having to be reset on loss of AC power they are the best from the standpoint of readability.
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The clock in my car is synced to a satellite signal or maybe several. It is always spot on with the Greenwich time signal beeps that the BBC sends out.
A little tale - mods be kind.
We had the "fall back" last weekend. Grand girls were here and in the pandemonium, adjusting the clocks and watches was not top of the agenda. We, the whole bunch including dog, set out for the supermarket to get there for 10:00 when it opens. It's no more than a 10 minute trip. I glanced at the car clock - 08:50. It did the fall back. Even if the clocks in the house were mains synced, they wouldn't have made the correction.
So the dog got an extra long walk with two extra little charmers...........:D

gar said:
When using instruments to make measurements one needs some knowledge of how the instrument works to allow interpretation of unexpected results.
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Totally agree.
 
ggunn said:
Yes, I have several of them. I also have a couple of reel to reel tape machines that have AC synchronous motors. One of them has a 50/60 Hz switch on the back but the other doesn't. I haven't used them in many years, though.
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Ah, life moves on.............:)
 
171102-1619 EDT

When I made the meter measurements this morning it was interesting that just holding the meter probes in fee space near the CNC that the meter was reading 60.02 Hz or whatever was the present frequency was.

The scope and I are going to the shop now to see what the waveform looks like.

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171102-2126 EDT

To repeat our shop has a two transformer 240 V three phase open delta with a wild leg.

Unexpected first big surprise was how clean the sine wave was. No major flattening of the peaks as I see at home. Probably many fewer computers and other capacitor input power supplies on the shop substation compared to the substation supplying my home.

The sine waves from both the 120 V circuit, line to neutral, and the wild leg to neutral were clean, and basically undistorted. The wild leg appeared to be very close to a 90 degree shift from the 120 V, as expected.

Played a little more with the Fluke 87. I believe the frequency measurement problem with the Fluke, and possibly the original poster is the following:

Using AC voltage mode. Power on to AC volts. Probe the voltage. Let auto-range pick the correct range by measuring the voltage. While in this state press the frequency button. The frequency measures correctly.

Alternatively, manually set the range. With no applied voltage press frequency button. Apply voltage and frequency reads correctly. Remove voltage, go to a different voltage of sufficient magnitude, and frequency reads correctly.

I believe what happens with the Fluke is that: if range is not set for an appropriate voltage setting before going to frequency mode, then that range remains at its setting at the time of selecting frequency mode. If that voltage range is low, and a large voltage is applied, then amplifier saturation occurs, and frequency measurement gets screwed up. This is present conjecture.

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