Power Canadians Use?

Exactly the same as 99% of the US for residential and commercial.

A bit higher voltage than the US (575VAC/60Hz 3-phase vs. 480V/60Hz

3-phase) for industrial.

Euro standards were never used. Residential has been 117V to 120V/60Hz for more than 50 years, with 3-pin plugs and 2-blade polarized plugs adopted over the old unpolarized two-blade type at a similar time.

Best regards, Spehro Pefhany

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The US government sometimes takes instrumentation to Europe for various reasons, and brings it back. That is probably where this DMM came from. If it came this way, it is an OPT 345 unit. Make sure that you are using a 250ma fuse on 120V operation. The 120ma fuse it came with as an OPT 345, might not last too long.

Oh, you might want to open it up and check to see if it really has been switched to 120V operation. Some HP gear will work on 120V even when it is set for 240V.

The 50/60 Hz switch is there to improve the powerline noise rejection characteristics of the DMM. It will work in either position, but it will work better in the 60Hz position.

$75, crisp new box, foamed in place, with manual, and works too! Wahoo!

-Chuck Harris

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Thanks. That's what I figured. I removed the fuse and it's a 1/8 amp, which is what's used in the 240V model. It's working okay, tho. I've been perusing the op manual but it has mostly stuff abnout automated testing, not much on manual measurement.

I got out my couple dozen precision resistors, 400 ohms, 0.1%. I measured a few using the 4-wire method and they are about 400.25 ohms, which look like they're within tolerance. I had a few that I had measured on the Leeds Northrup wheatstone bridge, and they were a bit high, so I marked them with paint. I couldn't get an absolute resistance reading with the bridge, I just knew that the bridge was set for 400 and the null meter's needle was off to one side. The Fluke 4.5 digit DMM wasn't much good either beause of test lead resistance. But the 3478A gives 400.71 ohms, which is about .16% higher than 400, so this resistor is out of tolerance.

It's kind of weird watching the microvolts of 'noise' in the DC voltage of an AA cell.

[...]

I have recollections of when Ontario switched from 25Hz to 60Hz during the 50's. Every motor had to be rewound, and mobile crews went from house to house to do the work. This was a huge job, but there were fewer appliances then. My dad was a general contractor and had a large collection of motors salvaged from different work sites. Some of them were huge, but he wanted all of them converted. The hydro truck spent a long time at our place:)

Niagara Power's Rankine Generating Station is required by law to supply

25Hz as long as customers continue requesting it. A steel mill in Hamilton and a few other customers use it, but they will soon have to convert to 60Hz when the water rights expire.

Mike Monett

I guess I understand that if you have a lot of existing big motors or transformers you might not want to switch.

But other than that, is there any advantage to 25Hz? I would think that 60 Hz would be quite a lot more efficient in terms of the size, weight, and cost of motors and transformers, not to mention filter capacitors. Presumably as frequency continues to increase, capacitive losses in power distribution become an increasingly important factor; but that would affect the utility, not the consumer.

I suspect that the only differences are that 25 HZ is more efficient to transport, but that 60 Hz is more efficient to use, generate, and transform.

-

----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

-----------------------------------------------

Is rewinding all it takes? Isn't the number of coils critical?

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There dozens of ways you can fill the slots on an induction motor's field. If you take a 25Hz motor that was wound as a 2 pole motor (most were), and wind it as a 6 pole, 60Hz motor, you get approximately the same rpm and HP. The added advantage is you have an excessively large core, for 60Hz use, and as such it will run cooler, and have more reserve HP than it did as a

25Hz motor.

-Chuck

Thanks for your post, Chuck. I spent some time searching on rewinding motors for different frequencies and found no useful information.

Thanks to you, the mystery is now solved:)

Mike Monett

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But nowadays, with the variable speed controllers, couldn't the motor just be fed the pseudo sine wave that 'looks' like 25 Hz to the motor. Of course that might be more expensive than rewinding or just replacing the motor with a 60Hz one. And one other thought. If the 25Hz motor would run on 60Hz, but at a higher speed, then change the pulley to a smaller size.

Thid brings to mind the Liebert package A/C unit we have in the mainframe computer roon. A few years ago the contractor who maintains it said that the 20 ton unit used relay logic and old technology, and they couldn't get replacement parts for it. So what we did was buy another used but newer model, and over a holiday period we just pulled out the old, and plopped the 'new' one in its place. The boxes look identical on the outside except for the color, and the insides look pretty much the same, other than the control panel, which now has a UC based controller. I would have thought that the whole unit would not need to be replaced, only the controller. But apparently not so in this case.

And many of these motors and units are on roofs and places that need special equipment such as a crane to swap or upgrade them. Rewinding a motor isn't exactly the kind of work you do onsite, and it's not that easy. I thought that the windings on big 'dry' transformers and motors had to be vacuum impregnated with varnish or a newer higher tech equivalent. I'm just curious about this, that's all.

Watson- As you are probably aware CSA is a standards & conformance test lab. Some of there work involves tests on customers products for export to the EU. The DVM you have may have been used in one of the CSA labs where tests are done on those products. Alternatively, the DVM could have been calibrated by CSA for a customer building product for sale in the EU.

CSA was one of my better customers over many years. One of my larger sales at CSA was an EMI test system from R&S.

Cheers, John Stewart

Semiconductors are well on their way to replacing lots of old-school components. I was rather surprised to note that all of the "wall warts" on equipment acquired in the last year or two have miniature switchmode circuits inside the "plug" where there would have been a conventional iron- core transformer just a few years ago. Almost certainly because it is now easier to design and manufacture and cheaper than an old-fashioned iron-core transformer. And the lighter weight makes them cheaper to ship as well.

I believe that a change from 25 Hz to 60 Hz involves much more than just the speed of the motor.

Seems very odd that Liebert wouldn't have some sort of retro- fit scheme. OTOH, they sell more new units that way! :-)

But back on those days (nearly 100 years ago) motors and transformers were larger, more accessible, not potted, etc. And rewinding motors and transformers was a relatively common repair method so there was a source of experienced labor to do it. Rewinding large industrial motors is still done because it is still cheaper than replacement. There are motor rewinders listed in the phonebooks in most larger cities.

So the economics of rewinding on the spot vs. purchasing new replacements was a decision that likely made perfect sense 100 years ago, but wouldn't today.

A motor controller certainly could be used today, but not back in the '60s. Back then, they were either motor/generator units, or rather big SCR based units. Quite noisy, both electrically and sonically, and very expensive. The labor of a technician was cheap in comparison... though they can be rather noisy too ;-) ...

No, not that easy, but rewinding is usually done onsite for the bigger motors, even today. It is rather a chore to move a 2T motor off of the roof of a 10 story office building. The windings are wound with a simple machine that has a variable sized form. A whole set are done at once, with the individual windings daisy chained together. The winder then fits the new windings into the slots in a chained fashion. It goes pretty quick when you are setup to do the job.

I thought that the windings on big 'dry' transformers and motors

Varnish isn't necessary, what was done on the large older motors, was to use a cambric insulated wire, and wooden sticks and wedges to force the wire tightly into the slots. Shellac was often used to coat the wire in the exposed areas. But vacuum impregnation wasn't done. The advantage of shellac, is it can be dried by running current through the windings.

-Chuck Harris

Several years ago, early in the SMPS wall wart era, we got 5V 1A regulated adapters for the Miland 100MB media converters that we used to go from cat5 to fiber optic cable between several bldgs (this was when

3Com wanted a lot more money for a 100MB FO adapter for their switches). A few months later, on occasion we started losing a bldg from the network. We found that the wall warts were dying, so we contacted the company and found that they had to send replacements because the 1A adapters were being run too close their max current and were failing. We were not at all pleased because we would lose hundreds of users when one failed. So these new fangled adapters were _not_ popular with us at that time. But I guess things have improved considerably in that industry since then. [snip]

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Noisewise, _nothing_ could he worse than the controller that's on one bldg at work. The big air handler motor is next door to the telephone room where I have to work, and at certain times, the Danfoss controller is feeding that motor what sounds like a million elves inside, each with a tiny hammer plinking on a small steel anvil. This screaming, ringing sound makes it difficult for me or any of the telephone co techs to hear the tone tracer to trace down a pair of wires.

And then I've found that tracing wires next to a fluorescent light can be a whiny experience with the new electronic ballasts they use. :-O

[snip]

As an other person said it is the same as in the USA except for the higher voltage.

Being tested by CSA doesn't mean that is is used in Canada. It just means that the manufacturer wants to seel the product in Canada and not having his product banned. Usually if you have a product that is certified CSA, it is more secure than an product only certified by UL because CSA is much stricter. There are exceptions though and we can call that bribes. A few years back (in Buffalo) we had a call from someone at an hospital saying that a transformer in one of our microscopes caught on fire. I found that odd because I would do the strict CSA test on them and there was no way that would happen. I would never had let that go to production. We were certified by CSA to do the test in house. I took one identical microscope and did the output short circuit test on the transformer and it caught on fire and had toxic fumes. Normally the transformer is supposed to open somewhere so the power is cut.

In Canada is is illegal to sell products that are not CSA (ACNOR) certified.

The company had started to outsource to China. The microscope had CSA and UL stickers. Thinking that something illegal was going on I called CSA in Toronto (Canada) and was told to mind my own business.

These people at CSA are so strict so I was stunned that this occured. For me when a product comes from China, the UL or CSA sticker doesn't mean shit.

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It's more likely to be valid when you cross-check the file number (there has to be a file number) with CSA or UL and make sure that

a) It's actually a valid number

b) It actually has something to do with the particular company

c) It actually refers to the product line that you found the sticker on

Best regards, Spehro Pefhany

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"it's the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com