Ive seen the tach on the machine cause this issue-not the Resolver usually, but the tach. I would start there.

are you getting a audible beeps from the drive?

I agree with replacing the Tach, or check the wheel and coupling on the Tach, then if they are ok, replace the Tach.

I dont recall getting any beeps from the drive, but i will check that out. the building has 3 cars and is empty, i only service it once every 3 months, the tach was my first thought, but wanted to ask the Kone guys just to be sure. What is the Resolver, and where is it located? i noticed on the drive cabinet it has the resolver angle written down 53 degrees. i looked at the sheave in the hoist way, and only saw one tach/encoder on the sheave. thanks for the help, i may go there next week to check it out just for the fun of it. ha ha i googled resolver, and found a good article on wikepedia.

It's inside the machine Scott. It's what the tach compares itself too. During the learn process the drive "finds it for the

check gov tach also

thanks guys, finally got to read a short training manual on this drive unit. did a quick read, looks like i will have alot of studying to do. i do have a few questions though. the machine i have is a mx20, it says in the manual that the resolver is built into the machine with no bearings or anything mechanical to wear out. Is this something that fails frequently?, if so, is it easily replaced? another question is, does the resolver also function as the position encoder for the system? I have not read anything about the function of the governor tach as aqua dog indicated. is this more of a safety monitoring device, or does it also work its way into the drive feedback system? another stupid question, while i was inspecting the car, i noticed when i stopped, the machine would move what seems to be a few inches side to side. is this normal? also, vatorman, i read the part in the manual about the audible beeps, that may help you find a problem, i will pay more attention next visit, I am really starting to feel sorry for the young guys, this unit seems to be quite sophisticated, i will have to spend quite a bit of time, studying in order to comprehend all that is going on here. Oh how i long for the days of the 6850 selector. Ha Ha

if I remember correctly the resolver tells the controller exactly where it is pertaining to the 360 degree's on the drive sheave. lets say the resolver is located at 70 degree's, the adjuster at setup will record this in a drive parameter. in machines without the resolver the car will lurch on inspection because it doesn,t quite know where it is until the tach movement tells it.Resolvers rarely go bad.

I had an MX20 that was shorted out internally.

It read only ONE ohm, between each of the motor's three phase legs, when disconnected from the drive. (A good car read well into the megohms, when checked the same way)

When the car ran, (yes, it DID run like this), it set up a tremendous vibration, hammering the cab, machine, control, floor, you name it.

The V3F25 was crowbaring it's output on max current, but as soon as the current flow subsided, it would turn on again, lather, rinse, repeat, lather...you get it. Only this would happen many times a second. So the motor had torque, then none, then torque, then none, all at a high frequency, which set up a resonant vibration throughout the elevator and building. Sounded like a huge jack hammer.

Although the motor was shorted, the short was on the "other side" of some portion of the windings, which meant that there was still some active and usable windings, that would create magnetism when energized, albeit only for an instant before the drive crowbarred off, then on, then off, etc. This allowed the drive to turn the motor, even though the motor was nearly a direct short. Staccato torque! Also, the meter just reads ohms, but since it is an inductive winding with AC being applied, there is then impedance, so that helps limit current flow, of course.

Funny how that drive can limit the current flow, and prevent fuses from blowing.

I don't believe a V2F25 can turn a MX motor without the resolvers' angular position feedback. It needs to know what angle the motor is at. I think it works something like a big stepping motor, where the drive will only alternate phases when it sees the angular rotation of the motor. The drives' output is dependent on the angular info, or it quits playing ball.

And if you connect an MX motor to a standard VVVF drive, I think it might just dither. Just a guess, because I never had a chance to test that theory. We will know more about this, yes, we will..when I have time..hah hah..

All of the kone mrl machines have resolvers. The issue of the car "jumping" on access is because of the brake slide and the result angle being lost. Once the tach, governor and resolver angle are in sync, all is well. Scott, I have only seen a bad resolver once at kone in ten years, and they replaced the whole machine. I do not believe they are replaceable. These systems use a governor encoder, and a tach on the machine sheave for comparison. The resolver is an "extra" necessity for the kone drive. The machine moving back and forth is a bad isolation pad underneath. Have fun changing that. It's a pain in the ass.

One quick check would to be swap the drive boards. Lots of connectors.

If you suspect the resolver is bad, try unplugging it from the drive, see if the problem changes.

When are you going to buy, steal, or borrow a scope? 🙂

Would be great for looking at tach feedback, pattern, motor current, etc.

Please check for o-ring on gov.tach before going nuts, I have several of said units. I always start there. Then tach brushes, bumpy feedback= bumpy ride. Never had resolver issues with any. Peace

8 ball,

Great idea!

Had that gov tach wheel o-ring disintegrate once also.

Good point, always start with the basics. Lest we forget!

thanks guys, i have been in this business for 27 years now, the more I think I know, the less i really know. Luckily the building has been vacant for a few years, the cars rarely run, this will give me the time to experiment when i do go out for service. thanks again i will keep you all posted as to the outcome, as long as i can remember. ha ha