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Discussion Starter · #1 ·
Ok so I have a hydraulic car hoist with a 240v single phase motor. The motor has no terminal block or labelling but has 4 wires coming from the windings and an earth.

At the moment it is wired and works fine under no load, I can operate the motor switch and the hoist will easily lift a car and stop at any height. The problem is once the motor has lifted a load it will not lift any higher it just stutters. The hoist has to go to the floor again to remove the load on the motor. Or it has to be bleeding down and whilst it's going down the motor will be able to start and lift.

I'm assuming it has to do with the wiring config. I'm a domestic sparky with no motor knowledge.

Help greatly appreciated.
 

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Ok so I have a hydraulic car hoist with a 240v single phase motor. The motor has no terminal block or labelling but has 4 wires coming from the windings and an earth.
How did you determine the proper wiring configuration?
 

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I'm assuming it has to do with the wiring config.
You may be correct, but I don't think I would assume that was the problem.

Does this motor drive a hydraulic pump which in turn operates pistons (the hydraulics that is)?

Since the motor will lift the vehicle when starting without a load or when the load is being lowered, I would take a look to see if the hydraulics is putting back-pressure on the pump which is keeping the motor from starting. If that's the case, then maybe there is a check valve that is sticking open?

We really need more information.
 
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Discussion Starter · #7 ·
You may be correct, but I don't think I would assume that was the problem.

Does this motor drive a hydraulic pump which in turn operates pistons (the hydraulics that is)?

Since the motor will lift the vehicle when starting without a load or when the load is being lowered, I would take a look to see if the hydraulics is putting back-pressure on the pump which is keeping the motor from starting. If that's the case, then maybe there is a check valve that is sticking open?

We really need more information.
Yes youre right about all that. Ive only had a little look at it but before I go back I want to cover all bases. Is there a wiring diagram I can look at or something.
What should I be looking for to fix bsck pressure
 

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Yes youre right about all that. Ive only had a little look at it but before I go back I want to cover all bases. Is there a wiring diagram I can look at or something.
What should I be looking for to fix bsck pressure
It is hard to say w/out looking at the unit. I would get the name of the lift manufacturer and call them. They will usually help you troubleshoot or at least explain the operation of their unit so you can troubleshoot.
 

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[del]Has the wiring been tampered with? or has it worked fine in the past?

Did you test the Cap? measure OK?

Check valves / lack of oil / blockage in hydraulics?

What amperage is the motor drawing in fault condition?

Winding resistance? Does the motor jump from start to run windings? could be issue with centrifugal switch.

Maybe call in an expert? (not having a go at ya, you'd run rings around an industrial sparky in with domestic work, whereas this is bread and butter work for an industrial sparky..)[/del]

Edit: I see it's a brand new installation, whoops, missed that part.

Can you draw the wiring diagram, I'm having a hard time ID'ing the connections on that terminal strip...
 

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Most likely problem.
This is an IEC motor, meaning it was NOT designed for use here in the US. It is rated 240V 50Hz (as far as I can tell, the photo is fuzzy but the nameplate is typical European, no mention of UL etc.). When you apply 60Hz power to a motor designed for 50Hz, the ratio of Volts per Hz is now lower than what the motor was designed for by 20%; it was designed around a ratio of 4.8 V/Hz (240/50), but at 240V 60Hz it is only getting 4.0 V/Hz (240/60). This affects the motor torque output, and most importantly, it affects the PEAK torque output by the square of the difference. So when fully loaded, ie starting with the lift up, the motor is only capable of 64% (.8 x .8) of its rated peak torque (160%-220% of Full Load Torque), right when you need it the most and the motor begins to stall, making the hydraulics stutter. When the lift is lowered and starting with no load, the loss of torque is less significant because the pump has no back pressure yet and it works.

Bottom line, someone got a killer deal on this lift, not knowing it was not designed to work here in the US. Happens a lot. You may need to buy him a new motor that will attach to that hydraulic pump, but that may not be easy if the motor is C-Face with metric dimensions. It might mean getting a US made hydraulic pump, then the hose fittings may need to be adapted.
 

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Most likely problem.
This is an IEC motor, meaning it was NOT designed for use here in the US. It is rated 240V 50Hz (as far as I can tell, the photo is fuzzy but the nameplate is typical European, no mention of UL etc.). When you apply 60Hz power to a motor designed for 50Hz, the ratio of Volts per Hz is now lower than what the motor was designed for by 20%; it was designed around a ratio of 4.8 V/Hz (240/50), but at 240V 60Hz it is only getting 4.0 V/Hz (240/60). This affects the motor torque output, and most importantly, it affects the PEAK torque output by the square of the difference. So when fully loaded, ie starting with the lift up, the motor is only capable of 64% (.8 x .8) of its rated peak torque (160%-220% of Full Load Torque), right when you need it the most and the motor begins to stall, making the hydraulics stutter. When the lift is lowered and starting with no load, the loss of torque is less significant because the pump has no back pressure yet and it works.

Bottom line, someone got a killer deal on this lift, not knowing it was not designed to work here in the US. Happens a lot. You may need to buy him a new motor that will attach to that hydraulic pump, but that may not be easy if the motor is C-Face with metric dimensions. It might mean getting a US made hydraulic pump, then the hose fittings may need to be adapted.
He's out of Australia
 

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bkmichael65 said:
He's out of Australia
Damn. I'm on the iPad ap and it doesn't show location.

Never mind...
 

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Discussion Starter · #16 ·
Hydraulics work perfectly going up and bleeding down. only when under pressure does the motor not start.

Theoretically should the motor be able to start with the full pressure of the hydraulic system against it? Has anyone used a similar setup and found it works fine?
 

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So there's only a problem under mechanical load? Seems JRaef should fit somehow....?

~CS~
 

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Hydraulics work perfectly going up and bleeding down. only when under pressure does the motor not start.

Theoretically should the motor be able to start with the full pressure of the hydraulic system against it? Has anyone used a similar setup and found it works fine?
Well, theoretically, if the motor is sized to start under load, then it should. But we know nothing about the hydraulic system, the pump size or the motor, other than the motor power rating.

Hydraulic pumps are what are called "Positive Displacement" pumps, usually gear pumps (there are meshing gears inside and the gaps between them push the fluid through). Because fluids don't compress, fluid that fails to move is exactly the same as any other mechanically coupled load that fails to move, it locks the motor rotor. When a PD pump is started then, there needs to be either some sort of bypass system for fluid to flow freely for a few seconds so that the motor can accelerate and then gradually increase pressure, or the pump must be over sized so that the initial torque output of the pump is high enough to push the fluid against the full back pressure. That's why I had suspected the loss of motor torque as the problem.

So not knowing what your system is, we can't tell from here if the problem is a bad design such as the motor being under sized, or the fluid bypass system is not working correctly.

Or it might still be a torque problem, if the motor starting capacitor is not providing enough initial voltage boost to accelerate the motor under full load to the point where the centrifugal switch kicks in (assuming here that it's a Capacitor Start single phase motor). That then could be from a poor choice in motors (design problem), incorrect wiring of the capacitor, or a failing capacitor. You're kind of on your own to discover the source of the problem by testing different things. That's probably the basis for the suggestions that you contact the lift supplier, they will know their own product and avoid your learning curve.

Good luck with it.

By the way, regarding the oil level issue:
The hydraulic system usually has some sort of reservoir, or what's called an "accumulator" that provides a place for the oil to go when the pump pumps it, and for the pump to pull from. If the capacity of the accumulator is such that you fill the lift ram before it gets to the top, once it is at the point where the oil runs out, there is nothing more to pump. So it WOULD work just fine UP TO that point.
 

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This might be a safeguard built within the circuitry. Maybe the designer wanted to make sure that there was no chance for the motor to run once the car was at the predetermined height for someone to step under it.

In other words, it might be circuit logic and nothing at all wrong with the components.
 
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