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  1. #46
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    Hi sossity,
    I think you need to talk to Tecalemit about their approval and your proposed modification as to whether it would be still valid to their approval. If not then do you want to go through the process of getting a new approval because of a design change?
    One main point in the discussion has been the failure of the drive during the operation of either going up or down, in particular the drive not responding to the input signal and continuing to operate. Some of the other comments have given suggestions on the input to the drive but not addressed the drive not responding to the signal. End limit switches have been discussed but they don’t address the situation of faults occurring between the end limits.
    You have raised the question of the system being failsafe and the drive being failsafe, look at this link where a Schneider drive has the STO features that I mentioned before. These type drives have functions and redundancy inbuilt to allow the drive to be configured into a circuit to achieve the desired safety level. http://www2.schneider-electric.com/resources/sites/SCHNEIDER_ELECTRIC/content/live/FAQS/237000/FA237443/en_US/S1A45606.pdf
    I have not seen the control circuit of your hoist so it’s hard to totally comment on its integrity. Let’s say in its original design for three phase it has two interlocked contactors being up and down with the raise and lower pushbuttons, end limit switches wired into the coils of the contactors and an emergency stop pushbutton wired so it drops power to both coils when activated. This arrangement is not failsafe, either of the contactors can weld and the input switches will have no effect. To be failsafe two contactors or even more would be needed for both the up and down contactors as well as a need for failsafe controllers wired to a control category 4 configuration to achieve this. I doubt that the circuit is configured this way.
    Is all of this doing your head in yet……………..
    Regards,
    Keith.

  2. #47
    Join Date
    Jun 2012
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    melbourne
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    Hi Keith,
    yes, the whole thing goes round in circles in my head and has done for the last 6 months. That Schneider drive looks ideal but being Schneider will cost more than my hoist did. I always said this was not about safety though, only compliance, and this design approval number seems to make it illegal to do any modification. An obvious modification would definitely attract attention, a single phase motor perhaps less so. I'd like to think it would never come to that. I gave it a go last weekend again and my existing motor is now making a clattering noise, not happy at all. I still say a single phase motor already at full speed should raise the hoist especially at less than half load. If I can fix the motor, then the choice is obvious. Tecalemit is an expensive manufacturer. They do have a single phase 4kw motor option, I'm sure they would love to retrofit it for me and then there would be no compliance issue, because they will already have the design approval number.
    On the contactor welding issue, I'm sure I saw a bit in the standard that said switches should be designed to make it impossible for them to weld together. I seem to remember that because I thought, how can something be impossible. Everyone knows a million to one chance crops up nine times out of ten. Anyway, it all comes down to that approval number, they must have convinced the authorities it was safe, and it may be that AS1418 is only a recommendation and not actually a legal requirement. I never found that out.
    I have probably made my hoist illegal by fitting a single phase motor, but if it ever came to it, it might be worth a lawyers time to argue if it was safe. Probably not, I'm not worth very much, I think they would pay out of sympathy.

    To be honest, if the single phase thing doesn't workout, I will use the original motor and a vfd (try for half power full torque at 30Hz, see if that theory works). The thing is just so handy. I did a clutch over xmas - I might have been tempted to try that without the hoist if I didn't already have it, but it would have killed me. Too old, too fat, can't even fit under the car!

  3. #48
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    Hi sossity,
    I think the phone call to Tecalemit to see what they have to say about modifications and their approvals would give you a clear picture of what your options are.
    I would be interested to see a circuit layout of your hoist in its original state so then the suggestions that have been made could be adapted to the circuit with minimum change to original and this just might be ok with them.
    Another option is to ring WorkCover and speak to an inspector, one who knows about Vehicle Hoists and see what they say about modifications.

    Keith.

  4. #49
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    Jul 2006
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    Athelstone, SA 5076
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    Quote Originally Posted by Keith_W View Post
    Another option is to ring WorkCover and speak to an inspector, one who knows about Vehicle Hoists and see what they say about modifications.

    Keith.
    .

    Based on my personal experience, I very much doubt Workcover, the Safework mobs or any other govt department will tell one what to do, what is allowed, whats not etc etc...all they will do is wait for the Sh*& to hit the fan and then find someone to pin on.
    My experience also tells me that that they do not care about near misses either!!

  5. #50
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    Athelstone, SA 5076
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    Quote Originally Posted by BobL;1918443


    [ATTACH=CONFIG
    366732[/ATTACH]
    I hope your going to tidy all that cabling up one day..even a few cable ties wont go astray

  6. #51
    BobL is online now Member: Blue and white apron brigade
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    Quote Originally Posted by eskimo View Post
    I hope your going to tidy all that cabling up one day..even a few cable ties wont go astray
    Yeah its an old photo from when I first set it up. It's all tied down now. I've even covered the mains wires with the missing outer sheath!

    RE: Worksafe.
    Asking for advice will result in being told vague things like you have to comply with the relevant OHS regs.
    If you are not a place of employment they may not even want to know about it,

  7. #52
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    Oct 2015
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    Pallamallawa NSW
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    AS / NZS 1418.9:1996
    2.11 ELECTRICA L EQUIPMENT AND CONTROLS
    Electrical equipment and controls incorporated in vehicle hoists shall comply with the requirements for electrical equipment and controls given in AS 1418.1.

    The operative part here is:

    "Electrical equipment and controls incorporated in vehicle hoists"

    The VFD is not incorporated into the vehicle hoist, it is part of the workshop supply.

    Cheers
    Richard

  8. #53
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    Apr 2014
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    Little River
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    Comparing a 3ph induction motor with a single phase motor, when it is loaded up to above the rated power, both motors will start to "slip" meaning that they will slow down.

    The 3ph motor will inherently try to come back up to speed so it will keep going overloaded but the single phase motor requires a starter winding to be switched on to accelerate it up to speed so it will stall.

    3ph motors can often be run for a short time above their rated power but a single phase motor will stall.

    In the case of a motor that is lifting a car hoist the duty cycle is very short and the manufacturer can overload it just to get a better figure for advertising purposes.

    So if you are replacing a 3ph motor that is run at full power or sometimes slightly above full power then you will require a larger single phase motor just to guarantee that it will keep going.

    To work out how much larger you need to measure the current at max load and from that work out what the true power being used is.

    Another problem is that the motor manufacturer may be going cheap on the amount or quality of steel in the motor so at full power it is already slipping severely and it is border line at rating that they give it.

  9. #54
    BobL is online now Member: Blue and white apron brigade
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    Quote Originally Posted by Bohdan View Post
    3ph motors can often be run for a short time above their rated power but a single phase motor will stall.
    I haven't noticed this with my motor testing where all motors are run to the stall point.
    When an SP motor stalls the centrifugal switch kicks back in anyway.

    Single phase motors can usually easily exceed their rated power and keep working for for just as long as 3P motors.
    Both types of motors will quickly heat up and if a 3P motor has proper over current protection on it this will kick in and turn the motor off.
    Single phase motors usually have thermal cut out on them that will eventually cut their power.

    Here is a HP/RPM curve for a 1490 RPM SP motor rated at 1.3HP.
    The 1.3 HP rating is reached @ about 1425 RPM and by applying more back torque it generated > 1.4HP and would have sat there working away until the thermal cut out had kicked in.
    Applying even greater back torque the RPM dropped to ~1350 PM the power dropped to just over 1.3 RPM and would also have kept working until the the thermal cut out had kicked in
    Screen Shot 2017-08-11 at 3.56.29 pm.png

  10. #55
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    Excuse me for the long story here. I wanted to come back and finish this in case anyone else is having problems with a converted hoist. There was not much on the web about converting hoists form 3phase to single phase, but hopefully this might help anyone who tries this afterwards. What I did find on the web certainly helped me so here's something back.

    I always suspected the motor as being faulty, even though it was brand new and would run and take a fair bit of load. I couldn't get past the fact that power is power, and single phase 2.2kw should lift the same as 3phase 2.2kw, once it is running, so in my mind, power is power, no starting involved. (The hoist takes no load as it starts until the car is lifted off the suspension). Anyway, the reason I was suspicious of the motor was because I had converted my 2.2kw 3Ph star wound mill motor to delta, and when I did that, I could see that one of the poles had never been working. This was because when they welded the copper wires together, one of the wires had burnt back about ¼” and was clearly not joined, not by a mile. I’ve practiced a lot with light gauge welding, and although welding copper wires isn’t hard when you know how, its not something everyone can do. At the time I saw the motor in my 30 year old mill and it had been running all its life at lower power, I though thought there would be quite a lot of motors running out there that are not capable of full power because of bad welding.

    A couple of weekends ago, I finally made the effort to take the motor down off the hoist. It was easier than I thought, although putting it back was just as hard as I expected, because its at the top of one of the hoist posts.
    When I checked out the motor, the run and start capacitors both read the correct uf on a dvm. I came up with the idea of putting the caps on a megger, and the start cap had high resistance after it was charged but the run cap had only 20k and wouldn’t charge over 50V, on the 250V setting. I got a new capacitor. I noticed the motor was hard to turn over by fingertips. If I opened the motor end caps just 0.5mm, it turned over fine. I ended up taking 0.5mm off the inside of the end cap. I also replaced the bearings which were cheap chinese (same as the motor) . The rotor run out was oK at 0.03mm although one bearing also had radial play of 0.03 also (separate to the run out on the rotor), and felt very loose. I suspect its because they were soft metal and had been run with a lot of preload pushing sideways so had worn in just minutes of use.
    The centrifugal switch had welded on one contact and burnt as permanent open on the other. The effect was I got high volts on the start cap even the motor was disconnected which gave me a nice surprise.

    The motor coils checked out ok on a megger, and with u1 to u2 the same resistance as z1 to z2. It shouldn’t have been but I haven’t looked at motor design at all for 30 years and didn’t know better. The wire gauge was the same for the U coil as the Z coil so it seemed reasonable.
    I put it back together and it ran with a horrible shriek. I should go back and say when I first tried the motor to lift a 1.5 ton van, it lifted about 1.2tons by my guess, then gave up. The motor was relatively quiet. As I tested things, after about 20 tests/lifts it began to shriek. This was still there after I fixed the bearings the run capacitor and the centrifugal switch. Even with no load on the bench.
    I thought the shriek was due to electrical imbalance because it went away immediately I switched off even though the motor was still running down.
    So I was back to my original suspicion, one of the windings was not welded correctly which would cause the imbalance. You can see here the motor looks ok when I opened it up. If you think the coils look discoloured or burnt, they definitely don’t in real life. Just like new really. Well, it is a new motor.

    20170914_113127.jpg

    I had to cut all the lacing away and of course it was the last junction I took off that had the problem. This is normal for me. If there are two outcomes, I always get the wrong one first. Lucky people say you make your own luck. People like me say they are tossers. You can see here that one of the junctions covered with fiberglass tube is burnt.

    20170914_121335.jpg

    It turns out I was right, and the welding was pretty bad. Id guess they hadn’t cleaned the enamel off the copper properly at all, and in any case, you need a certain level of skill to weld copper wire this thin. Something like this could not be done by a robot so I think its likely to be done badly in cheap motors. In my opinion, there will be many motors out there that are not running to their full potential due to bad welding, but how many are run at full load to know?
    In the next picture, you can see on the left the colour of the original welds. This is actually after I cleaned it up with a fibreglass pen.

    20170914_123014.jpg

    One wire must not have been connected or maybe originally connected through a very thin section which was heating up and going high resistance and losing power. This was the split phase coil and I suspect would cause an unbalanced ripple current in the capacitor and probably that’s why the capacitor was gubbed. ‘Scuse the photos. I have a cheap old phone as a camera just now and I just couldn’t get it to focus. Later on I put a bit of paper behind it so it would focus a bit better. On the right, you can see my new weld after I cleaned everything. There is no comparison in quality, but you might need to take my word due to the bad photos. After welding the junctions properly, I got 2.4ohms on the split phase coil and 1.6 on the main coil. Initially, I thought that burnt section had burnt the insulation off the side of one of the poles where I couldn’t see it. In the end I used the megger again, with the earth on a metal rod down the side of the pole where the burn would have been, and the positive on the coil. Testing showed no problem with insulation, so no damage elsewhere from that burning. I was not sure about the different resistance values though and thought maybe there was more damage somewhere. I had asked for advice from a member on here and he was sure the coils would not be the same, only on 3 phase would they be the same, and he convinced me to go to the effort of lacing up the coils again and give it a go. I was getting a bit pessimistic after all this I must admit.

    I did lace it all up again. Gives you all sorts of little cuts due to the sharp aluminium and you need to pull the string very tight. Took me about 2 hours to do this and get it all rigid and glued.

    20170915_101619.jpg

    Did it work? Do fish drink water!

    20170916_142104.jpg

    It can lift my 1 ton car no problems at all. The motor doesn’t even slow down as it takes the load. It can even start it when it is already half up. I think with the 1.5ton van, I might be a struggle to start it once its half up, but everyone else I read about that’s converted from 3 phase motor to single phase motor live with that and just lower the vehicle and take another run at it to get it higher.

    I know what you are thinking, if I had a mate we could just lift that wee car onto a couple of boxes, no need for a hoist. What can I say - billy no mates here

    So, I think I can conclude this means power is power and a single phase 2.2kw motor will lift the same thing as a 2.2kw 3 phase motor. It won’t start under as high a load as the 3phase motor though. The moral of the story is if you buy new cheap chinese thing for an unknown system (and not just a direct replacement in a known good system where a fault on new is obvious), you could be causing all sorts of problems making it hard to know what is at fault. I had completely rebuild the hoist and made new nuts for the screws and everything. There was a lot that could be causing the fault and I’d never seen the hoist run. i did a lot of checking of the hoist before taking the motor down because it was so heavy. Turns out it was the brand new motor.

  11. #56
    BobL is online now Member: Blue and white apron brigade
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    Quote Originally Posted by sossity View Post
    I had asked for advice from a member on here and he was sure the coils would not be the same, only on 3 phase would they be the same, and he convinced me to go to the effort of lacing up the coils again and give it a go. I was getting a bit pessimistic after all this I must admit.
    I dont recall saying that I, "was sure they would not be the same", more like "usually not the same".
    Anyway that's splitting hairs a bit and am really pleased you got it working.
    Well Done.

    Have you had a chance to asses the temperature rise of the motor at all?

  12. #57
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    Hi sossity,
    Glad that you have the hoist working as you want it.
    Interesting exercise on fault finding, as the motor is new did you think of returning it or was it out of warranty. Did you inform the place where you bought the motor of the manufacturing faults in their motor and seek some form of compensation for the work and investigations

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