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  1. #46
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    Jun 2005
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    Helensburgh
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    Just for giggles this is a current table I compiled today. My system is 150mm on the main duct and to my mitre saw and two ducts which are not are 125mm and 100mm because the machines cannot be altered to accept 150mm without huge internal changes or in one case (the overhead hood) the machine simply won't work with anything else which is a pain.

    Current Table.png

    It can be seen that the current draw does not appear to have peaked at 70hz but I am not pushing it any further. I am not qualified in VFD's or electrical matters and cannot comment on whether there are any differences between a single phase and three phase supply and what that may do to the results above but mine is three phase in and out.
    CHRIS

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  3. #47
    Join Date
    Jun 2010
    Location
    Canberra
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    769

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    I'm currently (no pun intended) waiting for one of these bad boys to turn up:
    Qingdao Hantek Electronic Co., Ltd.

    Good up to 20kHz they claim, although I think there's a thread on the EEV Blog that goes further into the actual bandwidth of the thing.

    Had ordered it to check the behaviour of my new TIG machine, but also might throw it on the odd VFD...

  4. #48
    Join Date
    Aug 2007
    Location
    Saskatoon, SK, Canada.
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    Gentlemen are surge suppressors required/advised for these VFD's? The question is prompted because I'm listening to lots of thunder in the distance and a spark to the lines this side of a fuse could fry things.

    Pete

  5. #49
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    Feb 2006
    Location
    Perth
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    Quote Originally Posted by QC Inspector View Post
    Gentlemen are surge suppressors required/advised for these VFD's? The question is prompted because I'm listening to lots of thunder in the distance and a spark to the lines this side of a fuse could fry things.

    Pete
    Surge protector are designed to protect against some hundreds of excess V in the supply but their effectiveness against lightening strikes is limited.
    The smaller and cheaper the suppressor unit the less likely it is to provide any sort of protection and there have been many cases of equipment still being damaged without the suppressor being affected, damaged or activated.
    Sometimes it's because that the suppressor was just junk, but another reason is because lightening can strike the ground or your home and generate electrical fields in air or on the ground large enough damage your hardware without going through the supply lines.

    I worked in a lab full of expensive and sensitive electronic gear where we had 2 x 20KvA suppressors and line conditioners to tidy up the mains power. About 10 years ago I was in the lab when lightening hit the carpark immediately outside the lab windows generating a dinner plate size crater and a puddle of molten asphalt around that. There was an almighty bang and a sheet of blue flame arced across one end of the lab. There was no visible damaged but it became quickly apparent that some sensitive stuff was toast and we managed to claim that on insurance. Other stuff seemed fine but over time that too started playing up but it was too late to claim that on insurance. Eventually we started having earthing problems and when we went to check on the earth strap (a copper strap with about a 25 x 10 mm cross section attached to the university copper mains water ring main pipes) immediately outside the lab we could see it was scorched. What we now believe happened is the lightening came back into the lab via the earth strap!
    In the end we had so much trouble with the the gear we retired it and ended up giving the gear to the Uni of Toronto geology department who came down and painstakingly took the gear apart and kept all the spare parts that they found useful and the rest got trashed. I still have the HD feet of the electronics racks in my shed.

    If you require lightening protection you should be using a specially lightening arrestor system

    VFDs are designed to protect themselves against some level of over voltages in the supply so they may cope with that to some extent without a surge suppressor. If VFDs are installed in a fully earthed metal enclosure with shielded cables that will provide some protection

    My recommendation is if you already have have a surge suppressor that is up to spec then use it otherwise I would not go out and buy one specifically for this purpose

  6. #50
    Join Date
    Jun 2010
    Location
    Canberra
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    769

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    I have a drive in a bore shed that has its own transformer hanging off the passing HV lines. That has a set of MOVs on the switchboard - I did look at more comprehensive protection, which involves spark gaps and delay elements, but it was suggested that the existing surge mitigation in the HV network and the lack of exposed LV wiring between the transformer and shed meant that it wouldn't be of much benefit. Not sure if that was entirely true, but anyway...

    The drive had a pressure sensor down the bore to sense the depth, the idea being that if the water level dropped too far while pumping, it'd wind back the speed to prevent pumping it dry. On one occasion there was an electrical storm many kilometers away - no strikes anywhere in the proximity of the shed - but the depth sensor and analogue input to the drive got zapped, my guess being that there was a surge carried through the aquifer from a strike far away.

    The moral of that story is that lightning does strange, unexpected things, and it's not a bad idea to use isolators for signal inputs.

  7. #51
    Join Date
    Aug 2007
    Location
    Saskatoon, SK, Canada.
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    I checked the panel (new house) and there doesn't appear to be any surge protection here unless it is in the meter box outside. I'm not going to sweat it for the moment. Next time I see the neighbour electrician I'll ask him what he thinks. With most every appliance in the house including the water, air and heat having tons of electronic controls in them it's a wonder why they aren't self protected. Or maybe they are and I don't know it.

    Pete

  8. #52
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    Quote Originally Posted by QC Inspector View Post
    I checked the panel (new house) and there doesn't appear to be any surge protection here unless it is in the meter box outside. I'm not going to sweat it for the moment. Next time I see the neighbour electrician I'll ask him what he thinks. With most every appliance in the house including the water, air and heat having tons of electronic controls in them it's a wonder why they aren't self protected. Or maybe they are and I don't know it. Pete
    Do you get much lightening your way?

    The fact that so little electronics has built in surge protection is an indication of the risks. Some areas are more risky that others when it may be worth spending the money on getting something but as what happened to us in the lab you can spend many thousands and still not be risk free.

  9. #53
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    Jan 2014
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    Sydney Upper North Shore
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    IMG_0704.jpg

    On page 4 of the manual, it states;

    "Lightning surge protection - the series inverter is equipped with lightning over current protection device, so it has the ability of self-protection to lightning induction. For the area where lightning is frequent, user should install extra protection in the front of the inverter."

  10. #54
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    Aug 2007
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    Saskatoon, SK, Canada.
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    I got my 4 K VFD last night and read that when I was skimming the manual. One of the few things I understood. I'll be getting one for the panel to protect the house. We get lightning often enough that it's justified I think. Sparking again yesterday and the thunder claps were only a few seconds after the flashes. Power flickered a few times. Now that I have the VFD to drive the CV-Max I can start putting the dust collection together between honey do tasks.

    Pete

  11. #55
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    Feb 2006
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    Perth
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    In the SAJ manual its says;

    "Thunder Stroke Protection
    Even there is protection device to protect inverter from induction thunder stroke, it's necessary for users in frequent thunder stroke area to install other protective device."

    The HY and Honeywell don't say anything about lightening strike.

  12. #56
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    Jan 2014
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    Sydney Upper North Shore
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    Default Number of poles

    Are most 2.2kW (3hp) 3 phase Motors 2 pole?

  13. #57
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    Perth
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    Quote Originally Posted by Lappa View Post
    Are most 2.2kW (3hp) 3 phase Motors 2 pole?
    Not necessarily, In my shed the 2.2kW BS is 1450 rpm (4 pole), the belt sander is 2900 rpm (2 pole), the 2 other 3HP motors I have are 4 pole.

    Pumps, dust extractors, table saws and some compressors usually use 2 pole.

    Air cons, BS, DPs, and lathes usually use 4 pole,

    One advantage of a 4 pole is you can get a better overall speed range with them than a 2 pole.

  14. #58
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    Jan 2014
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    Sydney Upper North Shore
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    Are those you mention, that you have in your shed, all 415v 3 phase?

  15. #59
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    Perth
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    Quote Originally Posted by Lappa View Post
    Are those you mention, that you have in your shed, all 415v 3 phase?
    They were but now they are 240V 3Phase.

    I have total of 17, 3 phase motors in my shed and all expect 3 have been converted to 240V 3P.
    One is a 415V 3P ∆ that cannot be converted to 240V ∆ with a complete rewire, one is a pump motor I got for free and is not in good shape so I might just dump that one, and one is part of a closed loop coolant system which will be converted WIGRTI.

  16. #60
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    Jan 2014
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    Sydney Upper North Shore
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    Default Wiring box on 3 phase motor

    I'm interested in a 3 phase motor which is some distance away. I've asked the guy to take a picture of the motor plaque but he says it's unreadable. He took the cover off the connection box and sent me this photo.
    Can you tell from this whether the motor can be easily converted to delta?.
    TIA
    IMG_0709.jpg

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