Home Forums General Discussion Technical Questions Persistent Vibration in Mitsubishi Lift

Hello All,

I would really appreciate an insight on the below problem.

We have a Mitsubishi Lift in a 22 story building that keeps having the problem of vibration. It feels like the car is stopping and then moving down or up.

We changed the ropes, the guide shoes of the car and counter weight as well as the pulley. We even tested the motor for vibrations and machined the motor bearing's casing. The motor is fine as we've replaced it with a new element yet the problem still exists.

It's been around a month we are trying to solve the problem and so far we haven't been able to stop this vibration and jerking.

I need help. Has anyone faced this problem before?
Can anyone give me an idea of what to check further?

Many thanks,

Hady

Wow. Who the heck sold you $25,000 worth of needless replacement parts? Where are you located? .

I agree with Philly, you need to isolate the problem. Is it directional? Is it mechanical? Have you gone through the parameters, you may have 1 or 2 out of whack. Is it a vibration in high speed, or does it only happen in a slower speed, have you replaced the velocity tach, I would do that first. you need to get a little more specific. Throwing parts at a problem is fine when you are out of ideas or good trouble shooting options. But you haven't begun to look at all the avenues before you replaced parts.

Hi John,

We have checked all the electrical components including the parameters and all are fine.

The lift vibrates at high speed.

The reason we changed the ropes and sheave is because we noticed that the ropes are twisting and when we release them we can see that they keep rotating till they are aligned again.

We have made all the possible diagnostics we can think of. We even tested the motor on a dynamometer for unusual NVH.

At present we are certainly out of ideas.

Can you think of anything other than a velocity tach? The vibration seems to be vertical as in the lift moves and then suddenly stops and then moves again and suddenly stops.

I really need some help. I am missing something.

Thanks for your reply,

Hady

I've forgotten to mention that the vibration can be felt more when the lift is loaded i.e. when one person is in it, it is not as severe as when 5 people are in.

I am not saying you should actually do this, but I once had a problem that was similar, I could not tell if the problem was mechanical or in the drive, I rode the car with the power off and had my helper lift the Brake by hand so it would drift in the up direction. Of course he dropped the Brake before it over sped. Did you replace the velocity encoder? does it drop the Brake when it stops and starts? Is this a geared machine? Are you registering any drive faults? Have you performed an auto tune? Sometimes a power module in the drive will be flaky and cause this type of problem, an auto tune will identify a bad one. Is the position encoder on the car top or the Governor, if its on the gov. check the rope and all the linkage, as well as the encoder coupling, and the velocity encoder coupling. This sounds like its a geared machine. Is it? what is the FPM of the unit.

Very interesting hady. I would be checking hoist motor supply for irregular voltage, current and frequency(if ac only)to see any abnormal drive supply. You do describe a stop/start action as well so I would've swapped the encoders firstly then the drive before any other action. You have changed guides and sheaves and I hope you also (while your at it) checked all the bearings for any abnormality. Since you have done this are they adjusted correctly and your not getting a safety gear rub? Its unlikely but who knows.

Its a hard fault but to me it indicates a drive or encoder issue particularly if the lift stops and starts.

My initial thought is encoder couplings and encoders. I'm amazed that was not first on the list. Second, if problem still persists, would be to hire a competent troubleshooting company to determine if it's mechanical or electrical by utilizing an oscilloscope and some electrical testing equipment hooked up to the drive. It's very simple to determine if the drive output is consistent with the proper tools. To me it sounds like a bad regen drive or a bad braking resistor. Twisting cables wouldn't cause a drive to shut down at high speed (they could've been un-twisted and properly re-tensioned without replacement) and neither would a bad bearing in any position besides possibly a governor and only if it has a gov encoder. Otherwise swapping the deflector, drive sheave and hoist motor machining/bearing was a really expensive guess. I'd call my company if I were you. Stop spending money until you find the right people for the job !