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Conversion of 3ph to 1 ph pulley& motor change 1

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texastom

Automotive
Dec 1, 2003
8
GB
I have a 3 phase single post car lift with a 2.5 HP 3kw 1500 rpm motor which operates a screw rod by a 9.5 inch triple pulley.
There is a 2.5 inch pulley on the motor which drives the large pulley by three V belts.
I need to know what size /single phase motor I need & what diameter pulley is required on the rod to make this work
I have spoken to the maker(Casco) but am unable to get the required information except that the pulley needs to be much larger (possibly 20inches plus).
Is there a formula or can someone advise me of what I need & where I can get the required bits
Thanks in advance
Ian L
Manchester
UK
 
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Ian,

Something here doesn't make sense to me - either you have a 2.5HP (1.85kW) motor, or a 3kW (4.0HP) motor, but not a 2.5HP (3kW) motor.

Having said that, I don't know what `Casco` are talking about. Surely, if a 3kW 3ph (or whatever) motor will do the job now, then it can be replaced directly with a 3kW 1ph motor, and will still do the job. No need to change any pulleys, or anything else for that matter. Provided your electrical system can cope with the change from 3ph to 1ph.

In other words, a 3kW motor in any language will output 3kW, regardless of how many phases it has.

You would need to change motor power and/or pulley sizes (ratio) if you wanted to lift more load than at present or lift the load faster, or both. Or, if either - you need to lift more load at less speed, or less load at more speed.

That is unless I am missing something here!

Hope this helps.

Regards,
Neilmo
 
Neilmo
Thanks you for your help.
The 3ph motor is 3kw My mistake
I have now found out that their 1ph unit uses a 2.2 kw motor for what reason I have no idea & a larger pulley .
Why not a 3kw 1 ph motor as you suggest
If I swap the motors & use a 2.2kw single phase motor what size pulley should I use.
What reason would there be to use a smaller output motor when converting to single phase
Thanks again
 
I would recommend that you buy a retrofit kit from the manufacturer so that they keep the liability for failures. Don't modify the lift with components of your own choosing and get someone hurt as a result of your lack of knowledge on drives and motors. Advice offered based on your limited information will not take into account the full function of the lift.
 
One good reason for using a smaller single phase motor is current draw. The higher current required by the single phase motor means heavier wiring. Reducing the motor size reduces the wiring requirement at the cost of performance.

If your wiring can handle it replace the current motor with a single phase one of the same power. If liability is a real concern get a single phase to three phase converter.
 
Thanks dvd for the advice which was not the information I was looking for. Liabilty for failures will be mine but I will have the lift certificated by the appropriate people after conversion.
I have spoken to the agents who have informed me of the differences between their 3ph & 1ph lifts
That is electric motor, drive pulley, pulley cover,drive belts & altering wiring.The other parts are common to both machines.Buying a retrofit kit is not cost effective & offers no advantages if I can get the correct information. Their costings for 1ph motor & the drive pulley are in excess of £1000 sterling(£670 motor £199 pulley £70 drive belts) which is why I am trying to go it alone(with your help)
Their guys admitted that these cost were very high & said I could source these parts elsewhere.
I have no intention of hurting anyone most importantly myself but thanks for your concern
Thanks & regards
Ian L
 
Hello to Iskit4iam
Thank you for your input & liability is not a concern a s the machine is out of warranty & they will not cover this conversion anyway.
I have nbeen told by various car lift engineers that 1ph to 3ph converters do not work too well with electro-mechanical car lifts. They say that they work well with lathes & drilling machines etc.
You are correct about the reduced prformance as the lifting time is increased from 40 sec to 50 secs with a 2.2kw single phase motor.
I intend to keep the 3ph wiring & and will change the wiring in the transformer from 380v setting to 220v setting
This wiring will cope with the additional current draw & I think I will use s 3kw single phase motor. If I use the same output motor albeit 1ph I may not need to change the pulley
 
Hello Ian,

Iskit4iam has hit the nail on the head, so to speak. He is quite correct in saying, that using a 1ph motor is down to current draw .

If you are still using your existing 3ph supply to run a 1ph motor, then I would suggest to just use a 3kW 1ph motor and change nothing else. However, (and this is what I missed), if you intend running your 1ph motor from a standard domestic supply 1ph 13amp socket (UK), then this limits your motor size to 2.2kW max.

For 13amps at 230volts and an efficiency of say 75%

Output from 1ph socket = 13 x 230 x 0.75 / 1000 = 2.2kW

Because you now only have 2.2kW available, instead of the original 3kW the lift will have to work more slowly to lift the same weight. So replace the 9.5" triple pulley on the screw rod with a 9.5 x 3 / 2.2 = 13" or larger pulley, so as not to overload your 13amp socket.

Hope this helps.

Regards,
Neilmo
 
Thank you for your polite response. Please bear in mind that as you increase the driven sheave diameter that the arc of contact with the driver sheave will be decreased, unless you change the center distance between driver and driven sheaves. This will require a higher belt tension to keep the belts from slipping on the driver sheave. The higher belt tension may result in an overhung load that is more than your smaller frame 1ph motor is designed for. Also if your lift requires a brakemotor the smaller motor may not have the required brake torque. Be careful. Your power transmission distributor will have software that can take all of these factors into consideration and properly size the drive for your lift.
 
Hello Neilmo & all
I am now in position to increase the size of the driven pulley as you have suggested. I have had a 30 amp supply installed so I won't be blowing any fuses

Do anyone know a supplier of triple V belt pulleys & suitable drive belts in the North West. I am in Manchester
Thanks for all your help.
I would not be at this stage without you guys
Regards & thanks again

Ian
 
Hello to all:
If you are having a 30 amp supply installed, Why change anything in the motor?
Besides that if you change your wiring at the transformer from 380 to 220V you are increasing the load on the wires by a 1.73 factor or decreasing the safe load to a motor that is 1.73 times less than at the 380 setting.
Up to now no one has pointed to the fact that probably your up and down switch has to make the motor turn CW & CCW and that requieres a different type of contactor setup, besides that in a 1 phase motor running on one direction you try to invert rotation instantaneously it will keep runing in the same direction unless you have a more sophisticated setup.
If your whole problems is not having three phase you could try the new generation of speed variators which imput 1 phase 220 or 380 and give 3 phase 220 or 380, allowing by the way to make soft starts which will minimize your peak starting current, and also you could adjust for several different speeds and to install end of run microswitches and so on.
To all who read this Just one year ago I didn't even knew that this one to three phases speed variator were availiable but I am using them in industrial enviroments, some even 24 hrs/day and had no problems with them.
One drawback, nothing is perfect right, is that when you use 1 phase input the line will draw 1.73 times the amps that it requieres to work but that can be limited by reducing the output top speed in programing the variator.
Another solution: want to lower amps used and have 3 phase availiable use a 2 HP - 6 pole design motor that turns at 1000 RPM's and you could keep all the pulleys, distances, belts and so on, and if you are lucky the output shaft of the new 2 HP should be the same as your actual 3 HP
 
Hello sacem
Thank you for your valuable input.
I was advised that the clever electrical devices you mention may be unreliable in these applications.
I have now changed the motor fro a 2.2Kw single phase motor so all talk of 3 ph is wasted
3 phase could be installed at a cost of £3500 Sterling +17.5%VAT
I am competent with electrics but not in this situation & was going to get an electrician to do it.
All the switch gear is in place from the 3ph application including end of run microswitches but instantaneous reversal is not a requirement
I need to switch the transformer to 220v & make some alterations as in the makers wiring diagram
I am not sure what the contactor is or does & would appreciate your help.
I can fax or mail you both 3ph & 1ph wiring plan if you can assist
Many thanks
Reagrds
Ian L
 
Hello Ian L.

Glad to help you, I'm on end of year vacations so my fax is not availiable until next Monday 5 if you want to fax my number is (511) 254 2953 you should manually ask for fax tone, maybe its easier to scan and e-mail me at sacem1@terra.com.pe and as soon as I check them I'll send you any observation I think you will need for correct operation.
A contactor is a device for closing an electrical circuit, usually is coil operated has one pair of contact points (from there the name) for every line that it has to control plus usually several auxiliary control lines to make the operation sequence, to keep it in actuated (Currect flowing to the motor) and to control it (interconected to overload relays that can be set for exact desired max load and so on)
They are usually used in industrial enviroments and can be operated from push buttons that can be far from the actual contactor.
The home equivalent would be a switch operated cicuit breaker.

Your decided on the 1 pole 2 Kw motor but for other set ups I can swear by those speed variators here in Peru you can buy one (German made) for up to 2 Kw for about 200 British pounds. I went crazy about your cost of going 3 phase, that change around here would be about 150 British pounds, top, and I thought we had very high installation costs.
Hope to hear from you.
Regards
SACEM1
 
Hello all
I have now fitted all the bits 2.2 Kw single phase 4 pole motor & a 13.5 inch pulley.
I have separated the switch gear contactors and wired in the contactors to switch the lve & neutral so as to produce clockwise & anti clockwise rotation but the motor only rotates one way
That is the ramp will only go up.
I know I have done soemthing wrong but I know not what.
Ithought that swithing Live & Neutral would reverse the rotation
What do I need to do now
Any help would be appreciated
 
HELLO TEXASTOM:

In my answer on Dec 30 I pointed to the fact that you had to turn CW and CCW and that this requiered for some single phase motors a sofisticated setup or control.

Every motor manufacturer states in its conection diagram which wires have to be switched to get the motor to turn CW or CCW they are internal wiring, not external lines like in three phase motors, thats why you have a more difficult set up some times with 2 auxiliary contactors to get the inversion done.

I offered to check your wiring diagram but have not received yet, include the diagram that comes with the motor because its different for every manufacturer and even for different power motors in the same manufacturer.

Lets hope you have not bought a single phase motor wich only turns in one direction and that are intended usually for operating pumps and blowers, that way the end user will not make a mistake when connecting the power and having a pump or blower not working correctly.

Cheers

SACEM1
 
Hello Sacem
Thanks you for your posting but I have no achieved the correct result. I did send the data twice but you obviously did not receive it
The motor does turns CW & CCW but the direction is controlled by two bridges between the terminals in the motor control box. It is made to turn in either direction but not both unless controlled from elsewhere. I removed the bridges & rewired the ramp switchgear via two contactors & the transformer. The left contactot for up movement & the right for down. Switching the transformer from 380v to 220v produced 24v for the control circuit
I used a triple pulley 400mm diameter which was as large as I could fit even though the makers suggested 455mm. The 455mm pulley would haved been in contact with the driving pulley on the motor.
Having said all that it now is working perfectly
Thanks for all your help everyone. Interesting that the guys who sold the motor did not have a clue that it could operate both ways & wanted to give me a full cash refund
Regards
Ian L
 
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