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Thread: strange voltages

  1. #1
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    strange voltages

    UPS tests.

    I connected the major tech MT250 to the UPs to get an idea of how long the batteries would last with a 50 watt lamp connected.

    This is where it got interesting ... I got some really strange reading on the display... take out the good old fluke meter and check... voltage is not a problem - 230 VAC on the fluke display ... however the major tech unit has voltages ranging from 165 - 186 VAC ... checked live to neutral ...neutral to earth ...live to earth ... then i realised it was a modified sine wave UPS.
    Comments are based on opinion...not always facts....that's why people use an alias.

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    A true RMS meter should pick up the correct voltages and I see they advertise as True RMS
    I would ask for my money back from Major Tech as it cannot be true rms -

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    It is not worth the hassle... this is why i dont waste my money buying major tech ...unless it has a K in the model number.
    Comments are based on opinion...not always facts....that's why people use an alias.

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    The fast rise time of a squarer waveform might not be compatible with the input circuitry of the MT250, I doubt they'd outright lie about it being true RMS if it wasn't but never say never. I think you've just got to be aware of the limitations of any particular tester your using and the suitability of it for the particular test you're doing. I've seen a couple of occasions where people got a whack from or caused flash damage to lighting on dimmer circuits because of the high frequencies of the power waveform being misinterpreted by the tester they were using.
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    I looked at the replacement value of the MT 250 (over R4k) ...i decided to send it to major tech workshop... lets wait and see what they say.

    Its handy for those silly jobs where you just need to monitor the geyser load for example or as in my case battery life of a UPS or inverter.

    I have considered purchasing an owl energy monitor ... not for accurate true RMS reading... but more logging and load profiles.
    Comments are based on opinion...not always facts....that's why people use an alias.

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    Hi
    I recently (feb) bought a 3 phase logger and was tossing between the different makes and types.Thought I had thought of everything but once I got it and played discovered I had not.
    If I had known covid was going to destroy cash flow I might have left it.

    I decided to not get one with a screen .Find a screen is an attraction to theft vs a box lying in a panel. Tossed between single and 3 phase and decide to go 3 phase as the price did not seem that much more until I decided to buy and extra set of CT's to measure between 1 and 100 Amps - Most came standard with higher rated CT's
    Ended up close to 60K
    What I should have checked is that it is 4 quadrant because with solar and batteries feeding back to grid the readings are a challenge to separate. The extra CT's will be useful and I still would stick to something without a screen if you are going to leave it in a panel to measure over a period of time.

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    Diamond Member AndyD's Avatar
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    I have a Chauvin Arnoux 3-phase data logger I paid over 60K for and that was a good few years ago but I rarely use it simply because of the high replacement price and being scared of it getting stolen when it's left on site to log. I also have a Zaptronix Lambda 4 quadrant meter and several sets of split CT's which make it capable of logging 3-phase supplies between 10Amps and 1000Amps, it costs about a tenth of the price of the Chauvin Arnoux but it's more than capable of high accuracy logging over a period of several weeks and I don't lose sleep when I leave it on site. As with you GCE, lessons learned the hard way.
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    I bought a fluke 435 back in 2006 ...thought it was gona take my business to another level ... when i started asking questions about the setup and parameters ... I realized nobody could answer ... I was the only person in SA with such a fancy meter which was capable of way more than anyone could figue out... it took me a couple of years to work it all out ... there was a small market for it ...electromechancia flooded the market with free testing and entry level testers ... made it impossible for me to charge for testing services ... I hear it didnt work out for them ...i started getting calls for testing again ... what I have found ... you need to be and electrical engineer with years of experience to figue what to do with the test results.

    The risk of connecting the neutral clamp at the back of a live 3000 amp panel in a sugar mill for example ...because you couldn't switch off ... also helped with the decision to can that idea ... just too risky for the peanuts they were prepared to pay... i recall the one day sweating and the droplets of sweat were dripping out the back of my rubber gloves onto the buzzbars ... for R2000 ... sorry mate i dont have a death wish anymore ...those days of thrills and spills ... trying to connect current clamps with my arms in the panel with just a pair of rubber gloves ... riding my motorbike at 300 km/hr ... dont happen unless the compensation is worth the risk.

    I have a few very expensive pieces of equipment (thermal imager and a fluke 435 PQA ...metrel PQA) which i only use for my current client base ...i no longer offer service to just anyone ...it is not worth risk leaving the equipment on site ... then you have to consider insurance.

    Personal i dont see a market in this country for accurate expensive PQA unless you work for big industrial companies who pay a retainer for your services.

    you know what is sad ... big companies watch me working with my equipment ...read my reports and think ...why pay for the services when they can do it themselves ...they go out and blow R100 k on the equipment ... they dont send staff for training ... realize how risky it is connecting the equipment ... have no idea how to set it up or what to do with the data ... then they call me and want a discounted price for me to use their equipment to do load profiles or PQ tests ... I give them the middle figue and move on.

    A lesson i have learnt over the years ... it takes years to learn stuff ...dont just give away your time ... it is the most valuable asset you have ... dont allow people to take advantage... people say but a doctor earns R2000 an hours because they have a degree... so how much is 20 years of experience worth ? We need to stop this belief that artisans are workers and dont deserve to be paid for their knowledge and experience ...but more important stop giving it away ... stand up for your rate.
    Comments are based on opinion...not always facts....that's why people use an alias.

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    Diamond Member AndyD's Avatar
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    Quote Originally Posted by ians View Post
    ...........The risk of connecting the neutral clamp at the back of a live 3000 amp panel in a sugar mill for example ...because you couldn't switch off ... also helped with the decision to can that idea ... just too risky for the peanuts they were prepared to pay... i recall the one day sweating and the droplets of sweat were dripping out the back of my rubber gloves onto the buzzbars ... for R2000 ... sorry mate i dont have a death wish anymore ...those days of thrills and spills ... trying to connect current clamps with my arms in the panel with just a pair of rubber gloves ...
    Open circuit CT's are killers, it wouldn't be unusual to see several kV on the unshunted secondary when it becomes fully saturated. They often breakdown completely and flash damage will occur which is almost guaranteed to ruin your day if you're in close proximity.
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    Quote Originally Posted by ians View Post

    A lesson i have learnt over the years ... it takes years to learn stuff ...dont just give away your time ... it is the most valuable asset you have ... dont allow people to take advantage... people say but a doctor earns R2000 an hours because they have a degree... so how much is 20 years of experience worth ? We need to stop this belief that artisans are workers and dont deserve to be paid for their knowledge and experience ...but more important stop giving it away ... stand up for your rate.
    Excellent post and exactly my view from experience. I used to be part of a energy management and control company. We actually wired up normal Enermax meters capable of recording kVA and kVAR. The connecting of CTs was very dangerous and thinking back it was among the most stupid things I've done in my life.

    Being a very analytical person I loved working with the data though because I loved working with Excel and drawing up graphs.


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