Variable speed hoist

[Stustoys]

Being lazy I wanted a electric crane, but wasnt happy with the way the cranes electric ones I have seen start and stop. So I figured I'd get a 415V 3 phase crane and put up with derating it a little and run it on a 240V VSD. Well what nice people the crane makers are, they bought the star point out for me. I've had it running in Star with the brake removed. The input wires are labeled W1, U1, V1, the star point is W2, U2, V2. Can I pair and "1" with any "2"(other than itself)? or is there a certain order they should be in? Another motor I have is set up W1 - V2, U1 - W2, V1 - U2. Maybe I should just copy that.
The brake solenoid works on 240V but I havent tried it any lower than that.(not sure what to do abut it yet. I'll have to test it to see what its actually for.

Seems to work very well, starts and stops very softly as you'd expect. I'll get it loaded up tomorrow and see how it goes.(and pretty up the wiring :D)

Hope it doees work because it would be a major pain to get it running on 3 phase again.
Stuart

[jhovel]

Just use a multimeter to confirm both ends of each of the three coils and then connect them in delta.
Joe

[RayG]

Hi Stuart,

If it's wrong, it wll just run backwards, and you will have created an anti-gravity machine... :)

Swap any two windings to restore normality to the universe...

Regards
Ray

[Keith_W]

Hi Stustoys,
I have attached a pdf on Motor Terminal Markings as well as some data on a Leroy Somer Brake Motor that you may find useful.

Regards,
Keith_W

[Stustoys]

Thanks guys. Strangely the motor runs much faster in Delta. I've not seen this before on motors I've changed.(maybe I don't have the VSD set correctly)
Worked out the brake is needed(not very surprising really), I just didn't have enough load on it yesterday to make it free wheel.
The motor will turn with the brake on, but even for me that's a little rough. I wired the brake across two phases but even at full speed it doesn't pull all the way in. So things aren't going to be as simple as it was looking in the beginning.

Nothing special in the other end Joe.

Stuart

[jhovel]

Stuart, just a thought (way of of my area of expertise):
what if you put a diode ir even a bridge rectifier in line with the brake solenoid?
Firstly that would increase the voltage applied and secondly it would provide a fixed direction magnetic flux field. My instinct tells me that a magnetic force which doesn't have to reverse 100 time a second could be stronger than one that does....
Joe

PS: many thanks or an enjoyable hour in your workshop and your company this afternoon! and for the presents!

[Stustoys]

Hi Joe,
Sounds like a plan. I'll have to see if I have a bridge/diodes with high enough V, current shouldn't be a problem. If the brake drags a little on start and stop I don't think I'd let that worry me. I'll just have to check what the minimum Hz is that fully closes the solenoid.

I've had a thought about the motor running slow in star. I think it might be something to do with the brake, it needs very little pressure to work and as the hoist was on its side the brake may have been on a little. Not that it matters, to fast is a problem easily fixed.

Was good to catch up. Now I have a little more shed space lol

Stuart

[Ropetangler]

Stuart, just a thought (way of of my area of expertise):
what if you put a diode ir even a bridge rectifier in line with the brake solenoid?
Firstly that would increase the voltage applied and secondly it would provide a fixed direction magnetic flux field. My instinct tells me that a magnetic force which doesn't have to reverse 100 time a second could be stronger than one that does....


Joe if I understand what you are saying, the bridge rectifier should marginally drop the voltage, but only by about 0.6 V, however a DC voltage will allow a much higher current, because the solenoid has inductance as a major part of its impedance. The impedance of an inductor rises with frequency, so if you insert a diode bridge, you will have pulsating ripple, but a predominant DC current, which will also likely saturate the inductance, and IIRC, when that happens, the impedance drops dramatically, and you will most likely burn out the solenoid in the absence of any current limiting. I may be mistaken, but I would hesitate to make that mod without the advice of someone who knows whats what.
Stuart it sounds like a great project. With most electric cranes these days, there is no gentle acceleration up to speed and a gentle decelleration to stop at the end. It could be incorporated I would have thought with inverter drives, but I have not seen it except in the older cranes with DC traction motors, and for big heavy loads they were the cats whiskers, they could lift off very gently, and place down a 30 tonne load as gently as a feather.
To try to achieve the same effect with the usual controls you have to keep dabbing the down button (say) as you set the load down. The problem with heavy loads, when the brake comes off, the load comes down and hits hard because the brake takes a finite time to activate, and the load is momentarily in a semi out of control mode till the brake comes on again and halts the now fairly quick descent of the load. I wish you well with your project, and look forward to hearing of your solutions
Rob.

[jhovel]

Rob,
as I said, this is way out of my area of actual knowledge.
Thanks for some of the insights.
I actually thought the voltage would go UP with a bridge rectifier not down (my experience). However, the issue with current limiting and inductance evade my understanding.... so Stuart, please look further into it before trying it - unless you can measure the current that is meant to go through the coil (e.g. on your 415V VFD) and then check that it doesn't go any higher on 240V fed DC. checking the pemperature is probably a good idea in any case - given that the brake may be off (solenoid on) for lengthy periods while you are lifting a load up high.
In any case, don't do anything to harm this piece of good gear on the mere basis of my 'gut feelings'!
Cheers,
Joe

[Stustoys]

impedance, inductor, saturate the inductance,

I remember why I hate AC now ;).


To try to achieve the same effect with the usual controls you have to keep ..................

Hi Rob,
I was thinking along these lines and a dragging brake on start and stop may turn out to be a good thing. I know I cant use "coasting stop" as of course the brake comes straight on and I'm back the the sudden stop(though likely you'd slow it down with the speed pot normally). I'll have a play with ramp times with a load on the hoist to see what the shortest ramp I can use is.

I had a good go at pulling a building down with "dabbing" the button. I was lifting about 2.2t and had the control box on the load, pressed the down button, load goes down switch opens, load stops with a bounce, closes switch, load goes down, opens switch. repeat at the freq the building is bouncing at... things really started to rattle around very quickly.(I guess there would be a "dont rest the contorl box on the load" rule somewhere)

Stuart

[Stustoys]

Hi Joe,
*As I understand it* AC voltages are normally giving in RMS. To get the peak voltage, RMSV x 1.414, so 240VRMS becomes 339Vpeak. So the number has gone up but its the same thing.... if that makes sense? Roughly, there is likely more to it but that about as deep as I go(and I may even have it completely wrong).
I'd thought about measuring current but I've no idea how AC current of a coil relates to its DC current carrying.
And to think 24 hours ago it was looking like I'd be finished by now lol

Stuart

[Combustor]

Hello Stu,
My limited understanding of the windings in AC solenoids, contactors etc. is that they are a centre tapped winding, and that one side of the AC supply will go to the centre tap and the other side will connect to both outer ends of the coil which are paired together, so that there is always one half of the AC cycle holding the coil in. Not sure what the effect of a diode in the circuit would be, but it may create two opposing DC fields in the coil. Guess there is one way to find out, so put a light fuse in the line and proceed with caution. Just my thoughts, Combustor.

[Ropetangler]

Rob,
as I said, this is way out of my area of actual knowledge.
Thanks for some of the insights.
I actually thought the voltage would go UP with a bridge rectifier not down (my experience).
Cheers,
Joe
Joe the voltage will rise higher if the output of the bridge rectifier is fed into a capacitor. As Stuart has said, AC voltage waveforms normally have their voltages expressed as RMS volts, which is the DC voltage which would have the same effect in a purely resistant load. For a sinusoidal waveform the RMS voltage is 0.707 of the peak voltage above or below 0V. In other words, half the peak to peak voltage X 0.707.
When a capacitor is charged by the output of a bridge rectifier, it will charge to the peak voltage, which is 1.4 X the RMS voltage (√2) X RMS.
There is a small voltage drop of around 0.7V per conducting diode, in a normal bridge rectifier there are 4 diodes, but only 2 conduct at any one time. the first pair conduct on the +ve half cycle and the other pair conduct on the -ve half cycle. This is much more significant at low voltages , but is less significant in power circuits. Clear as mud I dare say:wink:. Regards,
Rob.

[Ropetangler]

Hello Stu,
My limited understanding of the windings in AC solenoids, contactors etc. is that they are a centre tapped winding, and that one side of the AC supply will go to the centre tap and the other side will connect to both outer ends of the coil which are paired together, so that there is always one half of the AC cycle holding the coil in. Not sure what the effect of a diode in the circuit would be, but it may create two opposing DC fields in the coil. Guess there is one way to find out, so put a light fuse in the line and proceed with caution. Just my thoughts, Combustor.
That does not sound right to me Combustor, you would just have 2coils in parallel. When the voltage went through the zero point, both windings would have the same 0 volts across them.
This is not my field of expertise, and I may well be wrong, now where is RayG when you ant him?:D

[Ropetangler]

I remember why I hate AC now ;).


Hi Rob,
I was thinking along these lines and a dragging brake on start and stop may turn out to be a good thing. I know I cant use "coasting stop" as of course the brake comes straight on and I'm back the the sudden stop(though likely you'd slow it down with the speed pot normally). I'll have a play with ramp times with a load on the hoist to see what the shortest ramp I can use is.

I had a good go at pulling a building down with "dabbing" the button. I was lifting about 2.2t and had the control box on the load, pressed the down button, load goes down switch opens, load stops with a bounce, closes switch, load goes down, opens switch. repeat at the freq the building is bouncing at... things really started to rattle around very quickly.(I guess there would be a "dont rest the contorl box on the load" rule somewhere)

Stuart
Hi Stuart, that is an intriguing problem, you want slow ramp up and ramp down times, with the brake only activating when the motor has power cut, and releasing when power is applied. A relay with n.o. contacts to release the brake should do it as long as it still worked satisfactorily at the lowest frequency your inverter runs. It would be better if there was an output available which was active only when power was being output to the motor, say +5v or +12v, which would remove the frequency variation from the equation. I don't know enough about inverters to know if there is any such output available.
On the matter of resonance, it is indeed a powerful force, now Stuart I hope that you weren't riding that load of 2.2t were you:no:
Cheers,
Rob.:D

[Combustor]

May have omitted something there. In effect the 2 halves of the winding are wound in opposite directions. If you put AC power across a single coil, all you have is an 'effing big vibrator. Combustor.

[jhovel]

Rob and Stuart,
the Huanyang VFD has a 240V AC output - I think for a coolant pump. It completerely slipped my mind... You may be able to program that to be on while there is a three-phase output and off when not. From memory, it can be programmed to come on before or after the 3-phase starts or stops. Check your manual.
Cheers,
Joe

[Stustoys]

Hi Rob,
I didnt get time to test anything today but I think I'll need the brake to drag a little at start and stop.
I might be able to up the output V a little and if I drop the base Freq a little it will get to max V earlier....... might work, have to check the manual.

Hi Joe,
Trying to get my head around the manual now.

Stuart

[RayG]

Hi Stuart,

I have a friend who does crane control systems, and I could ask him what the control principle is if you like, but I seem to remember they us some kind of torque control to maintain the cable tension rather than straight out V/F style speed control.

Regards
Ray

[Stustoys]

As the saying goes, "first understand what the manufacturer intended"
I'm having third thoughts about how this brake does its thing. It must drag all the time or any large load would freewheel down as soon as the down button was pressed(unless its using the grid as a speed control with some regen braking?).

Hi Ray,
Any info would be great, though likely over my head.

Hi Joe,
Wow these manuals are bad. I think some of the 240V circuits might come in handy though. If I can just work out what goes where. One part of the manual says output, another part says input, terminals I cant find etc etc fun fun


Hi Rob,
No I wasnt riding on it, if I was I would have gone down along with the button so my finger wouldnt have come off and all would have been fine...........there you go, "its safer to ride the load" :wink:

Stuart

[Stustoys]

While talking with Phil about this on Saturday I had an idea that "maybe the brake isn't "off" when then load is being lowered. I was able to reconstruct the factory wiring enough to see that it would indeed be "off", pity.

Having done some testing with loads. Up to about 27kg the brake isn't needed and can be "off"* all the time. Above that the load start to free wheel. As I see it this leaves me with four or so choices.
1. Leave the brake "off", Derate the hoist to 25kgs(or 50kgs doubled) and call it done.
2. Leave the brake on and drive the load up and down against the brake. While this works I have no idea how long the brake will put up with this sort of thing.
3. Leaving the brake "off" and control lowering by lifting slow enough that the load still goes down. This seems to work but I've no idea how long the motor would put up with this sort of thing.(I've ordered some 4 turn 10k ohm pots which will hopefully increase control)
4. A bit of all the above with a switch that lets me use the brake as "normal", "always on" or "always off".

I haven't checked any further about current needed to switch the brake at 240V.

There seems to be a function on the VSD which might allow moving from for ro rev with the pot. Though I haven't got my head around it yet and maybe misunderstanding it.

*off brake wise, on electrically

Stuart

p.s. I'll have to redo the 27kgs brake "off" test as I dont think I removed the brake pack so it may have been dragging even thought it was "off"

[shedhappens]

"I haven't checked any further about current needed to switch the brake at 240V."

Stuart if you know the volts and can measure the ohms then won't ohms law tell you the current ?

[Stustoys]

Stuart if you know the volts and can measure the ohms then won't ohms law tell you the current ?
The short answer. In a solenoid I'm believe not.

Long answer. Has something to do with air gaps, reluctance and inductance........:D. Which I sort of have a handle on, but only just.
I found this link useful.
1 (http://robots.freehostia.com/Solenoids/SolenoidsBody.html)

Stuart

[shedhappens]

Stuart I have a clamp meter you can borrow if you like, it's nothing fancy (Jaycar) but it will do AC and DC, if your interested PM me

john

[Stustoys]

Hi John,

Thanks for the offer but I finially got around to testing it this evening.
444ohm coil which with simple ohms law would give me 540mA
Measured with wood holding the solenoid "open" 380mA.
"closed" 30mA. It buzzes pretty loud but holding it closed tight doesnt effect the current.
I'm pretty happy that wont burn the coil out(the good thing is if the coil burns out the brake comes on)

Tested with the brake plates removed completely. Now it free wheels down with almost no load.

I also tied out the reversing with the pot idea. doesnt seem to work(yet). Its 0Hz with the pot in the middle of its travel and goes to 50Hz either side, the leds change from Fwd to Rev but the motor runs the same way :( (hope that makes some sense)

More thinking.

Stuart

[shedhappens]

Good luck with it Stuart, sounds like a headache :doh:

give me a worm and wheel winch any day

[Ropetangler]

Hi John,

Thanks for the offer but I finially got around to testing it this evening.
444ohm coil which with simple ohms law would give me 540mA
Measured with wood holding the solenoid "open" 380mA.
"closed" 30mA. It buzzes pretty loud but holding it closed tight doesnt effect the current.
I'm pretty happy that wont burn the coil out(the good thing is if the coil burns out the brake comes on)

Tested with the brake plates removed completely. Now it free wheels down with almost no load.

I also tied out the reversing with the pot idea. doesnt seem to work(yet). Its 0Hz with the pot in the middle of its travel and goes to 50Hz either side, the leds change from Fwd to Rev but the motor runs the same way :( (hope that makes some sense)

More thinking.

Stuart
Hi Stuart, I think that it would be pretty common for a crane brake to drag a considerable amount when in the released position. This is what you have found to be the case with your project, and I feel it is quite normal. It is enough to hold in the case of your winch, 27kg, but you have to remember that the brake will be on the high speed side of the gearing, and due to the low duty cycle of most cranes, any subsequent heating will be minor and wear won't be much of an issue either, as the actual drag is not that much, it gets increased effect from the high ratio of the gearing.
What makes you think that the brake needs to drag when starting and stopping? I would have thought that when stopped you want it to fully activate, (but not necessarily instantly, because it is preferable to come to a gentle stop rather than a sudden, hit the wall type stop, which would put more load on the whole crane and lifting gear). This is often achieved by brake adjustments which allow the brake drum to make a turn or two as it brings the hoist to a stop, but still is on hard enough to hold the maximum load of the crane, and to stop that same load from its fastest decent speed in a timely manner.
Do you still think a relay which activates the brake mechanism when power is cut from the winch motor, and also releases as soon as power is applied to the winch motor, would cause operational issues, because it would seem to me to be easily done with minimal parts, if it works properly. I cant' see any potential issues, but that doesn't mean there aren't any:wink: Regards,
Rob

[Stustoys]

Thanks John,
I do have a chain block, but the chain is a pain. I also have a crank cable hoist but its damn slow*and fairly short travel*.

Hi Rob,
I'm coming around to your way of thinking re the brake and brake wear.

What makes you think that the brake needs to drag when starting and stopping? Depending on ramp times and what Hz you have the VSD on, with a load above 27kgs when you start to lift the load may freewheel until the VSD is up to speed and if the speed is set low enough it may keep going. I'll test full load with a manually switched brake(as I'm yet to work out how to use the 240V 3A terminals on the VSD) and see what happens



Do you still think a relay which activates the brake mechanism when power is cut from the winch motor, and also releases as soon as power is applied to the winch motor,
I'm not sure I understand this. Do you have it backwards? Power is applied to the brake to make it come off.

Current thinking is "normal mode" fast full speed movements with brake opperating as normal and a "slow mode" where the brake is left on and the vsd drives against it.
Subject to the test above.

Stuart

[Ropetangler]

Thanks John,
I do have a chain block, but the chain is a pain. I also have a crank cable hoist but its damn slow*and fairly short travel*.

Hi Rob,
I'm coming around to your way of thinking re the brake and brake wear.
Depending on ramp times and what Hz you have the VSD on, with a load above 27kgs when you start to lift the load may freewheel until the VSD is up to speed and if the speed is set low enough it may keep going. I'll test full load with a manually switched brake(as I'm yet to work out how to use the 240V 3A terminals on the VSD) and see what happens


I'm not sure I understand this. Do you have it backwards? Power is applied to the brake to make it come off.

Current thinking is "normal mode" fast full speed movements with brake opperating as normal and a "slow mode" where the brake is left on and the vsd drives against it.
Subject to the test above.

Stuart
G'Day Stuart, I will assume for the sake of this discussion, that we have a 50kg load which is suspended above ground level. I think that you are concerned the load may fall on initial powering of the motor in either the upward or downward directions. In the case of a gentle ramping up of frequency, I gather that you feel that gravity may overcome the winch motor, before it gets up to speed. I doubt that this will happen as although the motor is slowly ramping up, it will still be locked to whatever the instantaneous frequency is, and therefore it should not free-wheel. It is not like putting a very low voltage on a D.C. motor in a similar situation, in that case, the motor could be overcome by the forces against it until the voltage rose to the point that enough torque was produced to stop the run-away. With a VFD producing a low frequency output, there should be enough torque to stop any running away, provided that you don't go below 25 - 30 Hz if you are using the simpler V/Hz inverters, but if you use vector inverters, you could go right down to about 5Hz or even lower.
I would think that 25-30 Hz would give a smooth enough lift off considering the low ratio gearing involved.
on the other point you raised, I was referring to the brake mechanism, not the power to control it. As you say it is powered off, and applied by spring in the case of a brake on a crane, which is to provide some measure of "fail safe" braking. I might add, even this is not 100% foolproof, as an ex workmate of mine found to his surprise one day. He was controlling a big gantry crane with 3 hoists on it. Luckily he was using the pendant control for the crane this day, he could have been in an operators box, just below the gantry, at about maximum hook height, but on this day his Guardian Angel was on the job. He had just lifted out a large bronze roll weighing IIRC between 25 and about 33 tonnes, from a paper machine. The reason for the 3 winches, was to be able to pass the roll out through the paper machine frame. The process started with the gantry over the roll, and the 2 left hand winches took the weight of the roll, with the extreme left hand winch being up against the inside of the frame, on the LHS and the centre winch being about 1/4 of the way toward the LHS from the inside of the RHS frame. The roll was lifted, and moved right till the centre winch ropes were against the RH frame. The RH winch which was outside the frame , then took the weight of the RH end of the roll, and the centre winch was disconnected. The roll was then moved further out, till it was mostly out, and the centre winch hook could now go up and over the frame, ready to take the weight of the LH end of the roll when the LH winch ropes reached the inside of the RH frame. The LH end of the roll was transferred to the centre winch, run out into the centre of the machine hall, and then my workmate travelled it down the length toward the end of the building. When he went to stop it though, it kept going. He hit the emergency stop, and it still kept going. He then ran for all he was worth to the crane isolator switch, which thankfully stopped it all about 9 feet from the end of the tracks. We'll never know, but many thought it may have gone clean out of the building with that load on. The problem was that the main contacts had welded together, and the emergency stop was a magnetic no volt switch, but it could not stop it with the welded contacts. A good result in the end, but a very close shave.
Nighty Nite,
Rob

[PDW]

Good luck with it Stuart, sounds like a headache :doh:

give me a worm and wheel winch any day

Agree. I love the self-locking feature of them. Unless something shears, with a decent reduction ratio, you can't back-drive them.

I picked up a nice little 1/2HP 3 phase motor with integral planetary g/box over 20 years ago and I've kept it all this time awaiting the right project. As it can be jumpered to work off of 240V 3 phase, I may have found a role for it.

Powered anchor winch on my boat.

Note that I won't be relying on the planetary g/box to hold the load, it will (might) drive the manual anchor winch, which has pawls on the chain gypsy.

PDW

[Stustoys]

Hi Rob,

I think that you are concerned the load may fall on initial powering of the motor in either the upward or downward directions.
Thats it.


provided that you don't go below 25 - 30 Hz
I'm talking about much much slower than that.(or at least testing, what I end up with we'll have to wait and see)
With a load of over 27kgs and the brake "off", the load is lowered by lifting slowly enough that the motor slips backwards against the VSD(if that makes sense). I'll try some lowering tests at higher "down" speeds and see if I get any locking.


Stuart

[Ropetangler]

Hi Rob,

Thats it.


I'm talking about much much slower than that.(or at least testing, what I end up with we'll have to wait and see)
With a load of over 27kgs and the brake "off", the load is lowered by lifting slowly enough that the motor slips backwards against the VSD(if that makes sense). I'll try some lowering tests at higher "down" speeds and see if I get any locking.


Stuart
O.K. Stuart, I stand corrected then, I would not have thought that the motor would slip backwards against the VFD, even at low frequencies, as long as they were not so low that you lost stability of control. IIRC I have read somewhere the simpler VFDs work well down to around 25 - 30 Hz, and the vector types work down to 3 - 5 Hz, and in my mind I had thought that 30 Hz would give a pretty gentle deceleration or acceleration of the load, bearing in mind the final ratio of the gearing, and the fact that it works satisfactorily for most users at 50 Hz.
Do you have a vector drive you can try, that would let you set the low speeds much lower, and I suspect that it would be much harder for the motor to "slip" against it, than it might against a simple V/Hz inverter. I have not studied inverters all that much, but I imagine that there must be torque curves vs frequency published which should provide you with a fair idea of your chances of success. It is obviously more difficult than I thought it would be that's for sure. Cheers,
Rob.

[Stustoys]

Some numbers before I forget them

With an 80kg load the motor needs to be lifting at 15Hz to hold the load with the brake off. It loses about 3mm on start up, of course timing is everything I have the ramp set on 4 seconds*. While the load is 80kgs(on bathroom scales) it creeps, so I must be a little over its limit. I'll have to leave it now until I get the brake working with the VSD. Maybe all thats needed is a momentary switch to hold the brake "on" while the VSD gets up to speed in case you ever backed yourself into a cover where load was within 3mm of being down and you've stopped. But how often is that likely to happen?

Some of the time just being able to switch the brake "off" would allow you to lower the load fairly slowly. Of course you need more then 27kgs.

Stuart

*Since I wrote this I changed the ramp to 2 seconds and things not surprisingly improved but its hard to tell. For all I know even on 415V 3 phase the load may go down a little on start up?

[Stustoys]

As I understand it, simpler drives lose torque as the Hz gets lower, Vector drives dont lose as much.
30Hz isnt all that gentle, this thing moves! (I could get 25Hz effect by doubling the chain)
A vector drive might be part of the answer but I dont have one.
What I'm after is something that can do inches a minute not meters.

Also there is stopping. I have it set on coasting stop. A short ramp might be good for slow speeds(depending on how the brake ends up being set up), but that could be an issue are higher speeds. Although if you are lowering very slowly its likely the weight will be off the hoist before you stop anyway.

Will have to wait and see.

Stuart

[PDW]

As I understand it, simpler drives lose torque as the Hz gets lower, Vector drives dont lose as much.
30Hz isnt all that gentle, this thing moves! (I could get 25Hz effect by doubling the chain)
A vector drive might be part of the answer but I dont have one.
What I'm after is something that can do inches a minute not meters.


Worm or planetary gearbox driven by your electrical motor. Also gives you torque multiplication rather than subtraction.

Sounds to me like you're indulging in the 'I have a hammer to hand so everything needs to be a nail just because I have a hammer....'.

What problem are you trying to solve? Raising/lowering a load at slow speed under fine control, or trying to see what is possible with a VFD and a box of other electrical components? If it's the latter, fine, go for your life. I'm kind of planning on the same thing for my boat when experience tells me to just use hydraulics.

PDW

[Stustoys]

Yes it could be done with gearing......... then I dont have high speed.(though I could double the chain and run try running the motor at 100Hz) As yet I dont see that I need more torque.

In this case I bought the hammer to see if it is a cheap mod that can be done to other larger hammers.

The former with the later.

Stuart

[PDW]

Yes it could be done with gearing......... then I dont have high speed.(though I could double the chain and run try running the motor at 100Hz) As yet I dont see that I need more torque.



No but you said you wanted inches per minute, now you say that you also want high speed. Just what is your SOR for this device?

You simply are not going to get that speed range without gearing or some type of expensive control system - big DC motors and controls for example. You've already found the lower Hz limit of your existing setup and the speed is too great, plus (IIRC without reading back) you're still getting some sag. Since you can't go slower, you either have to increase motor torque by increasing size/HP to get more at a lower Hz, or go to gearing. There's no free lunch.

Like Rob I've had some exposure to 'real world' cranes where equipment had to be lowered or raised from a surface moving in 3 dimensions while the crane was also moving somewhat independently in 3 dimensions. Those cranes are seriously expensive. Your problem is a lot simpler but that doesn't mean that it's easily solved.

Even hydraulics have their limits. We once had an oceanographic winch installed that in practice had nothing like its rated pull as installed. We found this out *after* spooling out 1.5km of 12mm cable with over $100K of equipment on the end. Getting it all back aboard was not fun. Worked fine with only 400m of cable out which is what we did when we tested the damn thing in the Derwent before going to deep ocean.....

PDW

[Stustoys]

Bad thread name maybe. "Variable speed hoist"* may have been better. Want I want is everything, from full speed to hover, its yet to be seen just what I will end up with.

I have the speed range, its the starting that is currently the issue(and then only if you above 27kgs. At full load you need to have stopped where sagging about 3mm would be a problem), though the shorter ramp time seems to have improved that. If I can get the VSD to control the brake and if that control can be done with "Set freq reached", then I think it will be all good. I'll have to wait and see on that one until I get it wired up. I may even leave the brake on for very slow movement.. I'll see. Another option is the up and down switches are two stage, I could wire the brake to the second stage so it stays on until the button is presses right down.

As I said earlier I cant recall how much "real" cranes sag(if any). Though I do recall that they bounce that far when you take your finger off the button.

Stuart

*Ok now that just looks silly now that the threads name is "Variable speed hoist". I got up this morning and thought I was losing it and had to go back through my emails to be sure it had been "slow speed hoist" :rolleyes:. Thank you Mr Mod

[GuzziJohn]

As I understand it, simpler drives lose torque as the Hz gets lower, Vector drives dont lose as much.
30Hz isnt all that gentle, this thing moves! (I could get 25Hz effect by doubling the chain)
A vector drive might be part of the answer but I dont have one.
What I'm after is something that can do inches a minute not meters.

Stuart
Hi Stuart.

While a vector drive with a shaft encoder would be the ultimate solution you may be able to achive a suitable outcome with you existing drive. It seems as if the VSD may be configured for a variable torque aplication eg a fan or centrifugal pump. In this mode the available torque from the motor is greatly reduced as the speed is lowered.

For hoisting use you always need the same torque regardless of the speed ie constant torque mode.

Most modern drives can be setup in either configuration or somewere in between.

If you have a manual there may be parameters which will increase the volts/Hz ratio at lower speed to achieve this.

John

[Stustoys]

Hi John,
Thanks, I'd forgotten about those settings. I'll have a go at them when I get the brake set up, though I havent had a lot of luck with those setting on my other VSD....... but that doesnt mean much lol

Stuart

[Stustoys]

Success!!!!!!!! or at least I can see the light at the end of the tunnel*.
I've gone from Up/Down buttons with a pot for speed control to a Run button with the pot controlling both FWD(up)/REV(down) and speed.
Finally worked out the terminal switching(or at least enough so I can get the VSD to do what I want it to do) so the brake .
Time to make a new pendant, clean up the wiring and mount the VSD.

I hope the only thing left to decide whether the brake should be set to come of when the VSD gets a run command or when the VSD gets to it set Freq. Set freq is good except if you change the speed to fast the brake comes on until the VSD is back at speed. Not sure its a huge deal either way.

One last problem is the travel limit switch. The way is was set up it would inhibit running in one direction but allow it in the reverse direction at both ends of the chain. depending on the switches in the hoist I think I can sort it with one extra DPST button.

Stuart

* hope its not another train

[Stustoys]

Well its ungly but it works.
Sorted the over travel problem without having to add another switch, so all thats left is the small matter of cleaning up the wiring and mounting the VSD.

Stuart

[Stustoys]

Well its pretty much finished. Though the controls aren't.

174meg video (on its side, with crappy lighting... sorry but you'll get the idea) This is a full 80kg load. It will hoover cant get much slower than that ;)
vsh - YouTube (http://youtu.be/8v4XjnuPs34)

I have a 10 turn pot on it ATM which seems to work ok.

There is an issue below about 2hz, the motor cant hold the load so it starts to freewheel. Playing with settings should fix that(fingers crossed).

The only thing I really don't like and cant see a away around is if you lose a speed pot wire or the pot goes south, the VSD either goes to full speed up or full speed down.................

Stuart

Noticed something in the old wiring, it appears the primary of the transformer was wired to earth. (maybe that's it was for sale?) strange as it appears to be 415V.