Elevator Drive

[brian john]

I have a customer that recently updated their elevator system. They went from AC/DC motor generators to AC/DC drives.
This building is on the fringe of the utility service and has overhead distribution, so they experience numerous voltage sags. These voltage sags result in the drives for the elevators shutting down, they reboot and are operational again.

He has several frequency drives in the building and these all ride through these voltage sags.

I have asked him to verify with the elevator contractor the LV and UV settings.

But short of installing a UPS for these drives, is there anything others have run into that may minimize this issue?

I had a hydraulic elevator in the same neighborhood, that with the manufactures help we installed a UPS on the controls only and this resolved the voltage issue. So I am just looking for ideas.

 

[iwire]

It seems that if the elevator guys were cooperative (and they are not in my area) that they could simply widen the perimeters of the shutdown programing.

 

[dbuckley]

Bring back the motor generators! They had rotational inertia which reduced the sag

 

[iwire]

Bring back the motor generators! They had rotational inertia which reduced the sag

Yeah, they goofed things up bringing in the electronics. :grin:

 

[Electric-Light]

Check these out:

http://www.mceinc.com/DMS/Article\Tom\static_drives.pdf

http://www.elevatordrives.com/pdfs/replacing_motor-generator.pdf

Static drive can replace MG-set if the line can handle the sudden rise in current upon acceleration, but if it can't the flywheel effect is hard to replace.

 

[dbuckley]

Really interesting papers.

I thought the MG motor drive was ancient history, but one of those papers suggests you can still get that stuff.

As a kid I was facinated by the lift control panels at a railway station, these panels had many (brass!) buttons, and at the bottom of the panel was the start and stop buttons for the Ward-Leonard set , along with a lovely dark blue pilot light. Needless to say, finding out about Ward Leonard would have to wait till I was at tech college...

 

[brian john]

Check these out

Static drive can replace MG-set if the line can handle the sudden rise in current upon acceleration, but if it can't the flywheel effect is hard to replace.

Excellent THANK YOU

 

[charlietuna]

Are there line reactors installed on the drives?

 

[brian john]

I do not know, would this be a benefit?

 

[charlietuna]

We worked a large office building elevator conversion project and we had to add line reactors to help compensate the voltage drop. We ended up purchasing the reactors from the drive manufacturer and they doubled the warentee on the drives.

 

[wirenut1980]

I do not know, would this be a benefit?

Not for voltage sags. I would try to get a look at the parameters. If you are sure voltage sags are the culprit, try to see if there could be a time delay before trip programmed in for the undervoltage of around 1 second. If that cannot be done, I would try either an online UPS or CVT for the controls, but if the drive itself is susceptible to voltage sags, controls only mitigation probably is not possible, which will jack up the price of the mitigation.

 

[Electric-Light]

Not for voltage sags. I would try to get a look at the parameters. If you are sure voltage sags are the culprit, try to see if there could be a time delay before trip programmed in for the undervoltage of around 1 second. If that cannot be done, I would try either an online UPS or CVT for the controls, but if the drive itself is susceptible to voltage sags, controls only mitigation probably is not possible, which will jack up the price of the mitigation.

Let's just say you've got a car without enough horsepower to get over the hill, but you can do it by getting up to speed and using the momentum. That's exactly what the flywheel effect of MG-set does if the line can't provide the sudden load.

By using a static drive, you're basically stripping the car from the engine, so there is no momentum to help you up the hill.

 

[dbuckley]

There are companies out there that make rotating energy storage devices which can be used for this sort of application, commonly for the train operators, where they use the stored energy to get a train to move without drawing too much power from the utility.

In one of the papers linked to above (the second I think) there's a graph of current usage of a MG set and a static set overlaid, and its very demonstrative of the issue the OP faces.

As a possible suggestion to the OP's problem; could the elevator guys not set a slower acceleration on the lift?

 

[Electric-Light]

There are companies out there that make rotating energy storage devices which can be used for this sort of application, commonly for the train operators, where they use the stored energy to get a train to move without drawing too much power from the utility.

In one of the papers linked to above (the second I think) there's a graph of current usage of a MG set and a static set overlaid, and its very demonstrative of the issue the OP faces.

As a possible suggestion to the OP's problem; could the elevator guys not set a slower acceleration on the lift?

The adverse affect on functionality can be VERY substantial if these elevators make frequent stops.

 

[dbuckley]

The adverse affect on functionality can be VERY substantial if these elevators make frequent stops.

I'd certainly agree with that, the reduction in acceleration will mean less feet traveled per hour.

Depending on the OP's application, that may, or may not be an issue. But something has to give, and dropping performance on a lightly used lift may be more acceptable than spending money to fix the problem. Its a business decision.

For the customer, this must be a right growler: he's spent a good probably $$,$$$ for an "upgrade", and now the elevator is less good than it was prior to the "upgrade". And the chances are someone is going to want $,$$$ (or maybe even $$,$$$) to make it work again.

A building I worked in once had a UPS for one of the elevators, the one that the firemen may want to use, and some of the emergency lighting. I never took much notice of this UPS, as it wasn't one of "my" UPSs, but i don't recall it was anything special, just a standard double conversion UPS. I guess it was sized to comfortably take the loads including, for the elevator start current, as semiconductor UPSs really don't like step changes in load that take them near their maximum output.

It was fed via an ATS from the genset, so it in theory the UPS only had to paper over the gap betwixt utility failing and genset coming on line.