Single phase motor blows fuses under load

[jraef]

When was the last time you checked your filter to the hydraulic system? You may have a dirty filter causing cavitation and therefore the motor to over torque and send your amperage through the roof.

EXCELLENT point!

Hydraulic pumps on things like lifts are Positive Displacement gear pumps. If the gears are wearing out and shedding metal flakes, the filter gets clogged. Unlike a centrifugal pump that just loses flow so current drops, a PD pump just slugs it out and increases the motor current drastically.

 

[blackbird307]

While performing this test did you notice some of the timing of the details you mentioned.

"The car moved a little" and you mentioned the "motor sounded like it was having a really hard time". Did the car stop moving and then the "hard time" noise start then, or did the motor have the "hard time sound from the beginning?

From the very beginning I noticed it was having a hard time, sounded bogged down. One or two seconds later, fuse blown. I replaced the fuse, drove car off lift, and then started it again. I was able to make the lift move without a problem.

Check the service factor rating on the nameplate. If it is 1.15 or greater and/or the temp rise is 40 degrees C or less, then the overcurrent protection device may be 140% of FLA. All other motors would be 130% FLA. (NEC 2011 430.32 (C). So your fuses could be 21 amps, which are not made, so one is allowed to go to the next size up, which is 25 amps. Get a dual element time delay fuse to help with the inrush. Of course the same math applies to a circuit breaker.

The sad part is that there wasn't even a nameplate... just a sticker with spelling mistakes. Perhaps if I disassemble the enclosure ill see if there is one on the motor.


I took some voltage readings of the extension cord which I am using, there is hardly any voltage drop. I am going to try and see if I can take some current readings today once I pickup my current transformer. That motor should be only pulling around 10-15A at full load (according to some CSA tables). So if I take measurements of current, and it's close to that with hardly anything on the lift, then its definitely a mechanical problem, this may already be certain.

The lift is brand new, I just finished installing it. The instruction manual specifies R&O 32 Hydraulic oil, I put AW32 in because I could not find R&O specifically anywhere, (shouldn't make a difference). I greased pretty much everything. I greased the pulleys, the cables, and even the posts/guides aswell.

I am going to check the entire system for the above mentioned. If I can't solve/find a machanical problem I am going to take apart the motor and see what type of shaft it uses and find a stronger one of same frame.

The one leg of 220V wasn't my idea, I got it from talking to the obviously wrong person.

Thanks for the help.

 

[dlweber]

If it is brand new I would be in contact with the manufacturer before I started tearing apart and end up voiding any warranty there might be

 

[dlweber]

Most decent manufacturers will give some tech support, especially on larger items such as a car lift

 

[jraef]

... The sad part is that there wasn't even a nameplate... just a sticker with spelling mistakes. ...

Not a good sign.

 

[JRB]

You might look for a OPEN run capacitor as a possibility, this will allow the motor to start and run, but it won't be able
to produce the torque necessary when the motor is heavily loaded, and will draw current far beyond nameplate FLA. As the motor
can't maintain speed under load, you may hear what sounds like grinding and humming in the motor. The run capacitor will be
the smaller uF value of the two. If you are not familiar with them, sometimes they are contained in an oversized motor wiring
box, rather than on top of the motor with tubular metal covers. Usually the run capacitor is on the left, looking at the fan
end of the motor. Look for a "blown bubble" in the center of the capacitor. Check it with an ohmmeter for open.

You might also look for any type of flow control valve in the hydraulic system limiting return flow from the lift cylinder/s,
or left closed or partially open from the factory. Limiting return flow can increase motor current because the pump has to lift
the load and overcome return backpressure.

 

[JRB]

Also, because of your motor labeling issue, you might want to check if the motor is actually dual voltage, and currently connected for 230V

 

[blackbird307]

So I drove it back onto the lift, started it up...... now it works. Vehicle up all the way, no blown fuse. I don't know why? Maybe there was an air bubble?

 

[TL140]

Did you change anything since your last post?

 

[blackbird307]

Drove car off, moved it up and down twice. Drove car back on... and it works.

Thanks for the help!

 

[jraef]

Reminds me of that classic Windows programmer joke about restarting his stalled car by rolling the windows down and back up and the cars starts.

 

[mendonsy]

I had a good friend who ran a local repair shop for many years (now retired). He had a similar lift that refused to work several years ago. It wasn't tripping the circuit breaker, but the motor was stalling. It turned out to be a small stone that had become wedged in the scissors track preventing the lift from raising.

 

[DickDV]

While I'm glad its working for you, generally I just HATE it when a problem goes away like this. That's mainly due to the realization that it can come back just about that easy!

 

[ln3grls]

Car Lift

Hello,

I am new to this post and having the same problem with a scissor lift.
Circuit breaker on lift control panel blows. Lift goes up and down with no load, starts and stops as it is suppose to. With a load the lift will rise from a zero start position and lift car once in motion but will not raise car once loaded from a non zero position. I shorted out circuit breaker(on lift control panel) to eliminate the circuit breaker and motor does not blow the 40amp panel fuse nor does motor lift car, motor just hums.

Any help would be appreciated.
Lift is new out of box from China Jun.hv hoist

 

[blackbird307]

I overcame my problem. I gave the cables some small at the bottom and gave the lift a running start. If i stop midway and start again fuse blows. So the load is too large causing the motor to draw monstrously more current.