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  1. #16
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    Gearing the motor down 3:1 seems suitable to me. If you can lift x kg as it is then you should be able to get 3x after. It is a matter of time/money. Your choice. If it normally takes 90secs to raise (original motor) then it will take 4.5 mins to raise after conversion. I guess you have to hold your finger on the button all this time? That would probably annoy me pretty quickly, depending on how often it needs to be used.

    Dean

  2. #17
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    Jun 2008
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    The Whitsundays
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    Hi Sossity,

    I'd look at gearing the existing single phase motor down. I have looked at a 4kW single phase motor for an air compressor I bought. 4kw single phase motor has a starting current of around 125 amps! I doubt you want to go there given the likely 60 amp fuse in the service from the street.

    Cheers

    The Beryl Bloke
    Equipment er.... Projects I own

    Lathes - Sherline 4410 CNC
    Mills - Deckel FP2LB, Hardinge TM-UM, Sherline 2000 CNC.

  3. #18
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by Theberylbloke View Post
    Hi Sossity,

    I'd look at gearing the existing single phase motor down. I have looked at a 4kW single phase motor for an air compressor I bought. 4kw single phase motor has a starting current of around 125 amps! I doubt you want to go there given the likely 60 amp fuse in the service from the street.

    Cheers

    The Beryl Bloke
    You fuse should easily cope with that starting current because it should be specifically designed to cope with high start up current for a short period of time. My 2.2kW dust collector registers a start up current of over 60A but it is only connected to a 16A breaker.

  4. #19
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    Jun 2008
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    Default Loadings

    Quote Originally Posted by BobL View Post
    You fuse should easily cope with that starting current because it should be specifically designed to cope with high start up current for a short period of time. My 2.2kW dust collector registers a start up current of over 60A but it is only connected to a 16A breaker.
    The difference being that the service fuse already has all the electrical load of your property on it when you start your 4kw motor, you might get away with it, you might not. Do you know what the average load is in your house at the times you want to run your hoist? How well will you and your family cope if it's 42 degrees outside with the air conditioner & beer fridge not working until someone arrives to replace the fuse? how long will it take for them to get there and what is it likely to cost you in charges? Not to mention that the electricty distribution system in S.A. and NSW really needs extra load just at the moment.

    Cheers

    The Beryl Bloke
    Equipment er.... Projects I own

    Lathes - Sherline 4410 CNC
    Mills - Deckel FP2LB, Hardinge TM-UM, Sherline 2000 CNC.

  5. #20
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by Theberylbloke View Post
    The difference being that the service fuse already has all the electrical load of your property on it when you start your 4kw motor, you might get away with it, you might not. Do you know what the average load is in your house at the times you want to run your hoist? How well will you and your family cope if it's 42 degrees outside with the air conditioner & beer fridge not working until someone arrives to replace the fuse? how long will it take for them to get there and what is it likely to cost you in charges? Not to mention that the electricty distribution system in S.A. and NSW really needs extra load just at the moment.

    Cheers

    The Beryl Bloke
    If the correct breakers are installed they should easily be able to cope with this

    Here's an example of some breaker curves.
    A C type breaker can hold continuity for 7 times its rated current for up to 4 seconds before tripping out.
    At 4 times its rating it can hold continuity for over 10 seconds.

    So a 32A C type breaker should hold 128A for up to 4 seconds, which should cope with start up loads from large motors.

    Screen Shot 2017-02-14 at 6.48.26 AM.png

  6. #21
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    Jun 2008
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    Hi Bob,

    I agree whole heartedly that a 32A Type C circuit breaker would hold 128A for up to 7 seconds assuming there is no derating of the breaker. This will likely require the circuit to be wired in 4mm conductor rather than 2.5mm depending again on any derating factors that may crop up from the installation of said cable. 2.5mm conductor has a current rating of 28 amps (off the top of my head) if run on cable tray or other fully exposed to air situations. The use of a 32A breaker to protect 2.5mm cable would be defectable due to the fire risk involved, i.e. in the event of a fault within the cable or attached equipment, the cable my overheat and start a fire before the circuit breaker trips. Note that 32A is about 10% above the cable rating, this is a minor defect. At 20% above the cable rating it is a serious defect that requires disconnection of supply. The method of installation chosen for the cable run can be critical.

    Non the less, I was talking about the service fuse that is at the point of supply, i.e. out on the street, not the circuit breaker that is protecting the final sub circuit. It is possible that where Sossity lives his distribution entity uses circuit breakers instead of fuses for overload protection. It is possible that Sossity has a 63 amp Type D circuit breaker on his main switch board protecting the distribution entities service and Sossity's mains. It is possible that the distribution entity has used a 45, 50, 63 or 80 amp fuse to protect the service and mains. The service fuse could be on a pole in the street, the fascia or on the main switchboard. I have not been to Sossity's house and don't know which of these scenarios exist. I don't know what size or how long the service is. I don't know what size or how long his mains are. I don't know what sub mains are involved. Nor am I aware of any derating factors that should be applied because of installation methods. I do not know what the loop impedances are.

    Finally, I don't know what load is likely to be drawn by the other electrical items on his property when he turns on his hoist, it could be next to nothing or it could be 40 amps. This load has to be added to the starting current of the hoist for the purposes of circuit protection, voltage drop and cable sizing. It's this load added to the starting current of the 4kw motor, that will determine whether the service fuse blows or not.

    Given my ignorance of all of the above, I am happy to recommend Sossity gears down his 2.2kW single phase motor by say 3:1. I, personally, am not comfortable suggesting he install a 4kw motor. If you have done the necessary homework on this installation, having in place the prerequisite licenses and appropriate insurance, i.e. putting your money and livelyhood on the line, then I am more than happy to agree with your recommendation of a 4kw motor.

    Cheers

    The Beryl Bloke
    Equipment er.... Projects I own

    Lathes - Sherline 4410 CNC
    Mills - Deckel FP2LB, Hardinge TM-UM, Sherline 2000 CNC.

  7. #22
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    Jun 2012
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    melbourne
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    Hi Theberylbloke
    The 4kw motor was my idea and based on the equipment I already use, I thought it would be fine.
    I have a 40amp supply to my shed, which was installed years ago specifically to run a panel beating business until it got too big and he had to move out to a proper business area. It all looks professional and I remember being surprised at the gauge of wire they had used to the shed and it must have been in the days before copper got so expensive. The house itself has an 80 amp switch/breaker connected to the meter, which feeds the distribution board and subsequently the shed. Would that be the power board fuse you refer to?
    I have a 3kw (4hp) compressor which switches on as it pleases. I’ve had more than once where I just turn on the lathe and the compressor fires up too, so that would be a very high startup current combined. You know how these million to one chances crop up 9 times out of ten… Anyway, I always assumed I could do what I want and the 40 amp breaker would trip with no problem elsewhere, certainly not in the power companies side of things? I once tripped the 40 amp RCBO that feeds the shed at the house, but I traced that to the fact the welder torch was touching an earth when I powered up the welder, and its never happened again. God knows what the welder startup current is, I know it sometimes causes the lights to flicker when I switch it on. It’s a cheap Chinese 250amp/60amp plasma with no inrush current protection. Oh, and if the house is using 40 amps, there’s arses going to get kicked!
    We already have so many outages here, up to 15 hours at a time, I have a generator for the aircon and fridges etc. They charge me $3.50 a day for the power connection and I guess at least 10 outages a year - and this is a Melbourne suburb. I thought that was normal for Australia but people at work say they never get an outage.
    The thing I still don't know is, will a 4kw single phase motor have as high a start up torque as a 2.2kw 3phase motor wired in delta? I've not been able to find any figures on that side of motors. I'm also suspicious why my single phase motor can run at full speed as it lifts the wheels clear, then slow down over several inches until it stops suddenly. If it has higher peak torque than 3phase, and its already running at speed, shouldn't it be able to lift the thing? I understand why it ultimately stops quickly, but not why it also slows down slowly from full speed, if you know what I mean. That's my first port of call, to check out that motor physically because I don't think that's right.

  8. #23
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    Kryn, The other point to consider with fitting the VFD is if the motor is suitable?
    Is it an induction motor?
    Is it wired star or delta and can it be changed at the terminal box or will it require rewiring?

    This is all before connecting the VFD which could be considered the easy bit.




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  9. #24
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    Aug 2008
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    Oatley NSW
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    Hi sossity,
    Here is a link to a site that has some info on starting torque.Difference Between Single Phase and Three Phase Induction Motor - Circuit Globe
    Another site that may be of help. https://www.google.com.au/search?sou...+December+2014
    Where you say that it lifts for a bit, slows then stops, is it that the mechanical side, the screw nut and thread is binding causing the motor to draw more current and the overload trips.
    Could be mechanical as well as electrical concerns here.

    Keith.

  10. #25
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    Another good read is found athttp://www.microchip.com/wwwAppNotes/AppNotes.aspx?appnote=en012135
    Download the AN887 pdf.

    Keith.

  11. #26
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    melbourne
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    Thanks for the links keith, there looks to be lots of useful info in there.

    What i was really hoping for was an actual comparison of typical motor real time torque so i could guess if a 4kw 1ph starting torque was anywhere near a 2.2kw 3ph. I had a quick look at your links but couldn't find anything specific, but did you see something in there? I have looked a lot over 5 months and have lost the will tbh. I skimmed that pdf link and I think there is just about every graph except 3ph vs 1ph torque!

    I know exactly what you mean it could be the hoist and I worry about that. I refurbished the whole thing and even made new brass nuts for example. Everything is cleaned and greased. I am as confident there is nothing wrong as I can be I guess. When i manually wind it, the load comes on gradually as the suspension lifts - there is no sudden increase. The fact that its hard to wind up but easy to turn down, i take as a good sign that there is nothing binding more than it should.

    What it does, is with arms below the car on the ground, it will start and the motor picks up to full speed more or less straight away with no load. it will lift the car off the ground, and change pitch as it takes the load. it begins to sound like a car hoist if that doesn't sound daft. But once the wheels are clear of the ground (perhaps even before), it starts to slow audibly, but not a very fast rate of slowing, and it will do this while traveling 2 or 3 inches more. Then it stops with a bang, no slowing down gradually. An induction motor can only stand so much slipping, so no surprises in one way, but still, if it can run the load for several seconds while slowing just gradually, why is it doing that if it has the same average torque (and indeed higher peak torque) than a 3phase motor of the same power? The fact that it can complete even just one revolution but slow down just a bit, to me that means its not the same power as the 3phase one. That's the bit that makes me suspicious of that actual motor. It could be a mechanical problem too, but I can wind it down easily plus spent hours carefully checking everything. Although everything is heavy duty, its a pretty simple thing.

     

  12. #27
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    I don't know if there is a graph that shows both single and 3 phase on the same graph.
    Single phase motor is a two pole motor so to get the rotor turning you have two magnetic fields being generated where in three phase you have four poles so four magnetic fields being generated, this I am sure you have read several times.
    In the current situation you have do you access to a Tong Tester to see the amount of Current Draw you have, at startup, initial raising of the car then as you get higher. This may indicate any binding you get mechanically eg high spots on the tread on the shaft, shaft out of round etc that would cause the motor to stall.
    There then has been a lot said on the 4kW single phase motor option, and you will pull a lot of amps at startup typically 6 to 8 time FLC and because its a two pole the current will still be high if the motor is working under a big load. Remember the Circuit Breaker is only to monitor the Cable and if its a C Type limited inrush capability as show in previous posting, a D Curve Breaker is designed more for Motor Type applications.
    My option would be to look at a VSD as you can get ones with adjustable torque settings, has inbuilt Breaker so to speak and can be programed so you get a Soft-Start Type operation.

    Keith.

  13. #28
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    Hi Keith,
    The current behaves as expected except when it stalls it drops to 4.5amps. The manufacturer said it has a built in overload protection.
    I have mostly ruled out anything mechanical because I can lower the hoist under load fairly easily, but it’s hard to raise. There is no binding. I don’t have anything to compare it to though. At full load I can only just turn the 250mm pulley at the top by using both hands at the top of a ladder. I can lower it easily by just pushing the rim with one hand. Every component has been apart, cleaned and greased.
    I don’t want to use a vfd because my interpretation of AS1418:9 is that it would not meet australian standards and would therefore be non compliant. I can’t remember the details now, but I thought at the time it was pretty clear I wouldn’t be able to use a vfd and keep it within the regulations. I’m not saying it wouldn’t be safe, just that I couldn’t make it meet regulations on technicalities.
    I’ll start a post on this in the future once I get it sorted as I don’t have time right now. It’s a major job to take anything apart because of the weight (750kg) so it has over 600kg on me in a fight. You’ve made me rethink about things though and I can disconnect the chain and load up one side at a time to make sure they both have the same resistance. Other than that, it becomes a major project to check anything.
    Last edited by sossity; 16th Feb 2017 at 08:56 AM. Reason: Quoted wrong standard

  14. #29
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    Hi sossity,
    Understand that your busy and you will be looking at the control issues and motors latter when you have time.
    The Standards for Cranes and Hoists and in particular AS2550.9 for Electrical refers to AS1418.1 and I believe it allows for control where a VSD can be used as long as the circuit is configured so it fails to a safe state.
    For Cranes and Hoists the Standards get a bit messy with a lot of referring to other Standards so can get a bit confusing.

    Regards,
    Keith.

  15. #30
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    Sorry, I had quoted the incorrect standard, but you are right, you end up having to read various other standards. The very reference you mention is one of the points I consider make it non-compliant. How do you ensure a vfd will fail in a safe state? I could not consider a cheap device with logic in it incapable of failing such that it remains driving a motor for instance. In expensive electronics you can have any device monitored by other devices so overall the circuit will fail in a safe state, but as it stands, a vfd does not meet the requirement in my opinion. There are also other standards which dictate the buttons required, and buttons on a vfd do not conform. you can wire out to proper buttons but I don't think its safe to have two sets of buttons for instance. it goes on and on... I've got at least 5 months on you with this project, but you are on the same lines as I was Eventually you will end up going round and round same as me!

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