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Hard start 3 phase motor

Gpzmax

Plastic
Joined
May 2, 2022
I have an old automotive lift that uses a 5hp 3 phase motor. It turns a jack screw to lift the arms. I am running a 10hp rotary to power it. If there is no load, the motor will spin up and lift. IF I stop it and try to lift or lower it the motor will not get up to speed. I think I need to add some start capacitors to get it up to speed when under load. Would I need the caps on all three legs or just the generated one? I was considering using a timer relay set to say 2 seconds. I am looking to you all for your expertise. This 3 phase power is all new to me.
Thanks
 

dalmatiangirl61

Titanium
Joined
Jan 31, 2011
Location
BFE Nevada/San Marcos Tx
Probably best if you give more info on your system, start with power coming into your building (Volts and amps), wire sizes, breaker size, is your rotary just a 3ph motor, or a brand name rpc, etc etc etc. Most likely you need run capacitors. Give more info and some people here might be able to help.
 

Gpzmax

Plastic
Joined
May 2, 2022
Updated/additional information

Probably best if you give more info on your system, start with power coming into your building (Volts and amps), wire sizes, breaker size, is your rotary just a 3ph motor, or a brand name rpc, etc etc etc. Most likely you need run capacitors. Give more info and some people here might be able to help.

The power is coming from the main box, a 200 amp supply. This line is on a 60 amp breaker. From there it is 8 awg to the outlet. From the outlet I am running 10 awg to the 10hp 3 phase motor that I am using as a rotary phase converter. This motor is a 10hp Baldor X70421294010 rated at 28.2 amps. I have it wired for the low voltage, 208-230. I am supplying L1 and L2 with the 220 v from the main supply. I have measured 220v on each 3 legs out of the 10hp motor/rotary converter.
The lift is using a Leeson 5hp 3 phase motor, C184T17WC10A, wired for 230 volt, rated at 12.6 FLA and 14.4 SFA. Th lift is an older, screw lift. The lift motor has a 14 tooth sprocket with chain to a 55 tooth sprocket on top of the main column screw. At the bottom of his screw/leg there is a chain that runs over to the other leg to turn the screw there.
I have RONK static phase converter that I tried to use to power the lift motor. I struggled to get the running amps correct. The Ronk is designed for a constant load, and the motor pulls different amps depending on the weight of the vehicle being lifted. With my Rotary set-up, it lifts if I start the motor with no load on the lift arms. The issue is that once there is a load on the arms and I stop the lift, the motor does not get enough starting amps to get up to speed.
 

SomeoneSomewhere

Hot Rolled
Joined
Dec 24, 2019
Can you measure exact voltages while the lift motor is stalled? Obviously do this quickly to avoid overheating. This will tell us if you've got issues with excessive voltage drop.

#10 to the idler is pretty lightweight, especially if it's run any significant distance.
 

Gpzmax

Plastic
Joined
May 2, 2022
Can you measure exact voltages while the lift motor is stalled? Obviously do this quickly to avoid overheating. This will tell us if you've got issues with excessive voltage drop.

#10 to the idler is pretty lightweight, especially if it's run any significant distance.

Additional information

The 10 awg from the outlet to the rotary motor is about 6 foot in length. Amps that the rotary motor is pulling from the outlet on the 10awg wire to L1 and L2 is 23.3 amps. Voltages from the Rotary 10 hp measured at the Thermal overload for the lift are
L1-L2 = 237v
L1-L3 = 202v
L3-L2 = 208v

It does have 14awg form the magnetic reversing contactors to the lift motor if 5 feet of 14awg.

When I start the lift with no load I get the following readings
197v, 4.6 amp
187v, 16.8 amp
228v, 13.5 amp

When I then attempt to start the lift motor under load I get the following.
149v, 30.9 amp
133v, 71.9 amp
219v 77.7 amp
 

dalmatiangirl61

Titanium
Joined
Jan 31, 2011
Location
BFE Nevada/San Marcos Tx
Additional information

The 10 awg from the outlet to the rotary motor is about 6 foot in length. Amps that the rotary motor is pulling from the outlet on the 10awg wire to L1 and L2 is 23.3 amps. Voltages from the Rotary 10 hp measured at the Thermal overload for the lift are
L1-L2 = 237v
L1-L3 = 202v
L3-L2 = 208v

It does have 14awg form the magnetic reversing contactors to the lift motor if 5 feet of 14awg.

When I start the lift with no load I get the following readings
197v, 4.6 amp
187v, 16.8 amp
228v, 13.5 amp

When I then attempt to start the lift motor under load I get the following.
149v, 30.9 amp
133v, 71.9 amp
219v 77.7 amp

I think your wire sizes are too small, I'm no EE, but think they need to be sized for 3x run amperage to account for starting load. Sounds like runs are short so it should be easy to re-wire and see if that helps.
 

Gpzmax

Plastic
Joined
May 2, 2022
Can you measure exact voltages while the lift motor is stalled? Obviously do this quickly to avoid overheating. This will tell us if you've got issues with excessive voltage drop.

#10 to the idler is pretty lightweight, especially if it's run any significant distance.

Here are screen grabs of videos of the monito panel I created for the lift motor.

Motor started with No load. This will lift the car.
Lift no load pic.jpg

Motor attempted to start under load.
Lift under load pic.jpg
 

Gpzmax

Plastic
Joined
May 2, 2022
Can you measure exact voltages while the lift motor is stalled? Obviously do this quickly to avoid overheating. This will tell us if you've got issues with excessive voltage drop.

#10 to the idler is pretty lightweight, especially if it's run any significant distance.

Here are videos of the motor starting with no load and then it attempting to start with a load.

No load start

Under load attempt to start.
 

SomeoneSomewhere

Hot Rolled
Joined
Dec 24, 2019
220V at the motor on the utility legs with the motor stalled means there's no real concern of undersized cables.

But 140V on the manufactured legs means the RPC simply can't supply enough power. Someone else might comment but I don't think more capacitors can fix this. You need more motor, and probably quite a bit more. RPCs are not good at supplying the sheer current needed to start a motor across-the-line with a lot of torque.

Alternatively, there's a few other options. A bigger reduction ratio in the sprockets is one, but you'll end up with a slower lift.

A clutch between the motor and the chain would allow the motor to spin up unloaded, then have load applied at full speed. This would require some fabrication work.

Dropping the RPC and using a VFD would be ideal, but about $500. You'd also get the advantages of being able to inch the lift very slowly, and run above the normal speed when lightly loaded or descending.

Adding another idler would also be an option.
 

Jim Kennedy

Aluminum
Joined
Mar 16, 2008
Location
Marulan N.S.W. Australia
Hi Gpzmax. I would like some information on your Ronk static converter. Is it the Higher Voltage Autotransformer type with changeable taps and can you connect more or less Run capacitors. A picture of inside this converter would answer the above questions.
And was this hoist ever running with this Ronk connected to this 10 HP Idler Motor or only the Ronk connected to the hoist or only the 10HP as a RPC connected to the hoist.

Jim
 

Gpzmax

Plastic
Joined
May 2, 2022
Ronk Static phase converter

Hi Gpzmax. I would like some information on your Ronk static converter. Is it the Higher Voltage Autotransformer type with changeable taps and can you connect more or less Run capacitors. A picture of inside this converter would answer the above questions.
And was this hoist ever running with this Ronk connected to this 10 HP Idler Motor or only the Ronk connected to the hoist or only the 10HP as a RPC connected to the hoist.

Jim

I am not using the static to run my rotary converter. It is a Ronk 2S, Max HP-15, FLA-60amp, Model 80A, Input 240v, Output 240v.
20210615_173818.jpg20190911_140222.jpg20210916_155255.jpg

I have had it wired and powering the lift motor. I can set it up to run the motor with no load on the lift. I can also get it to lift a small car. But, when I put a greater load, larger car on it, it won't get up to speed. As per the documentation for the converter, I have changed the amount of start and or run capacitors and the tap. If I set it up for a large load then it doesn't act correctly for a light load. I have tried all kinds of different settings for the tap, 1-5, and each of the capacitor banks.

Since I had so much difficulty with this static converter I decided to try a rotary converter set-up. The Ronk was a free :) from a friend so it would be great if I could make it function for this. I have also built a different mount to enable me to utilize a 10hp motor on the lift. My thinking was that this would provide more power and use less of the capacity of the motor and might be easier to balance with the RONK.
 

13engines

Hot Rolled
Joined
Jun 30, 2015
Location
Saint Paul
Not sure if this applies to your rotary setup. Back when I was running a rotary phase convertor, (Store bought not home built) it had a toggle switch on it for starting. Once it was running you turned the switch off. The instructions said if running a heavy load or motor close to the rotary's rating, (like my big ole Shaper) it was best to leave the switch on the whole time. I'm pretty sure it switched in and out some capacitors. If you've got a start switch, try leaving it on.
 

BT Fabrication

Hot Rolled
Joined
Nov 3, 2019
there is a whole lot wrong going on here.
1 the motor is not getting 230V idling. so there is one problem (power caps or motor is dead)
2 the lift is drawing down the power below useable, driving up the amps and thus will fry the motor (too small of wire or converter?)
3 why are you bothering using this old style hoist. they make new modern ones, single phase hydraulic that take almost no power...(used hoists can be had for $1500) cheaper then converting and fixing all this )
 

Tony Quiring

Titanium
Joined
Nov 5, 2008
Location
Madera county california usa
Additional information

The 10 awg from the outlet to the rotary motor is about 6 foot in length. Amps that the rotary motor is pulling from the outlet on the 10awg wire to L1 and L2 is 23.3 amps. Voltages from the Rotary 10 hp measured at the Thermal overload for the lift are
L1-L2 = 237v
L1-L3 = 202v
L3-L2 = 208v

It does have 14awg form the magnetic reversing contactors to the lift motor if 5 feet of 14awg.

When I start the lift with no load I get the following readings
197v, 4.6 amp
187v, 16.8 amp
228v, 13.5 amp

When I then attempt to start the lift motor under load I get the following.
149v, 30.9 amp
133v, 71.9 amp
219v 77.7 amp
77 amps on a number 14 wire....what could go wrong...?

14 is rated for 15 amps.

Your meters are showing a lot of faults.

Unequal voltages and currents.

Step one is rewire.

Rotary is 10 hp supplying for 5 hp motor.

Starting current usually a multiple of normal.

Look up LRA locked rotor or other similar data on motor tag, or just find the largest one at rated voltage.

5 hp is about 16 amps at 240 VAC, Not a 3 phase guy so may be different.

Safe to maybe triple current for starting, so wire for 45 amps.

Number 10 wire on output of converter minimum.

Number 6 maybe on input, others can give better data here.

Our lift is. Hydrolic, large ram on one side chain to other side.

The motor is 3 hp maybe, been too long since we looked, the 1 ho rotary would not even start the motor.

5hp starts it just fine, with F250 on lift it still works well.

Your mechanical drive system will require higher starting current


Sent from my SM-G781V using Tapatalk
 

Jim Kennedy

Aluminum
Joined
Mar 16, 2008
Location
Marulan N.S.W. Australia
Ronk

Hi Gpzmax.
I think you would do best using your 15HP Ronk with proper valuing of the capacitors and transformer taps. The
autotransformer method is by far superior to the Idler type RPC for high torque starting. With starting capacitor values
(in microfarids) if too low it will not allow the motor to start and when too high the amps are excessive for no gain.
The manufacturers name was Add-A-Phase before it was RONK.
And please let us know when you get this sorted out and your hoist working.

Jim
 

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Jim Kennedy

Aluminum
Joined
Mar 16, 2008
Location
Marulan N.S.W. Australia
Ronk

4 more attachments.

Jim
 

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Jim Kennedy

Aluminum
Joined
Mar 16, 2008
Location
Marulan N.S.W. Australia
Hi Gpzmax. I would like to apologise for the attachments being so small, I've had alot of trouble with them, but if you would like to message me your email address I will resend them to you.

Jim
 

thermite

Diamond
Yes, there are electrical issues.. that #14 wire being used as a current-limiter or even "fuse" ....at the top of the list.

:)

That said, I suspect you ALSO have mechanical issues.

Cumulative wear... damage.. lube fail... distortion under load? Something that is causing binding when heavily loaded, such that the actual "present-day, REAL capacity", not the "as new, CLAIMED" capacity .... is being overly stressed mayhap?

"Heavier load" is exactly what it says it is, but there should otherwise not be THAT 'dramatic' a difference between initial lift, and resumed lift.

IF... it needs new parts... or is over-stressed, in general?

A whole 'nuther lift could indeed be cheaper and faster than the cost of f**k-around time and money with this one..

Dig deeper, first, into the source of the difference..

2CW
 








 
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