Elevator Phase Converter Large Voltage Drop

Z

zemingduan

Senior Member
Location
Philadelphia,PA
Occupation
Electrical Designer
We have a single phase 200A service for the house panel which feed the 20HP 208V 3ph elevator with 65.4 FLA and 311 LRA. We feed the elevator through the 50HP phase converter (American Rotary AUL - 50) and 30KVA 240V - 208V 3ph transformer. See below single line diagram. The phase converter is sized 2.5 times the motor horsepower for the inrush starting current. The transformer is sized to 125% of the elevator full load amps.

However during testing, the elevator company guy states the voltage drop at the elevator starter during the starting is too large and not acceptable. I think both the converter and transformer sizing are good. Any ideas and solutions?
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So the converter just sits and runs 24/7? IMO, none of this is a very good solution. The converter cannot handle that inrush without significant Vdrop and that's a fuction of those converters due to the capacitor bank. No way around that. You will either need a bigger converter, or I would put the motor on a VFD. Dump the transformer, input single phase to the VFD, and limit output voltage in settings to about 220V. The VFD has to be oversized for this, and it won't be cheap, but the result is a dramatic noise reduction and energy savings.

that converter will be pulling about 1100W continuously. Saves about $110/mo.
 
Here is another idea I thought of. That motor should be swapped for a single phase piece. They do exist. With all the infrastructure that has been added so far, just swapping that motor and making system adjustments seems the right choice. I don't know what system controls are in play, but I would bet this is not the first elevator needing to be installed on 1P power. I'd question the need for 20HP but not enough detail here as of yet.
 
zemingduan said:
Elevator motor data is here. View attachment 2579452
Click to expand...
Why the need for the 240-208 transformer, motor data says the motor is rated 200 230/460?
That transformer just puts more impedance in the supply line which will be at it's worst during motor starting.

I also agree that using a VFD to drive this motor and to do the phase conversion is likely the best route to use. Even if you wanted to run the motor @ 208 volts the drive could be set to do so.
 
That data says the motor is intended for Wye-Delta starting with an LRA of only 104A.

There is no need to oversize the transformer, although you do want to use a standard size, like your 30kVA. The TX has 24/7 losses as well.
 
fastline said:
not the first elevator needing to be installed on 1P power. I'd question the need for 20HP but not enough detail here as of yet
Click to expand...

I've seen passenger elevators running on single phase. also Plenty on DC for that matter. And 20 HP is more than enough for a horse elevator
 
fastline said:
So the converter just sits and runs 24/7? IMO, none of this is a very good solution. The converter cannot handle that inrush without significant Vdrop and that's a fuction of those converters due to the capacitor bank. No way around that. You will either need a bigger converter, or I would put the motor on a VFD. Dump the transformer, input single phase to the VFD, and limit output voltage in settings to about 220V. The VFD has to be oversized for this, and it won't be cheap, but the result is a dramatic noise reduction and energy savings.

that converter will be pulling about 1100W continuously. Saves about $110/mo.
Click to expand...
I sized the converter using the manufacture sizing tool that got the AUL - 50 (50 HP rotary phase converter). I also sent the elevator motor spec to the manufacture and they give the same sizing. This converter is sized based on the across the line starting. I feel wired that the elevator use wye delta starter which only 104A inrush during starting. There should be no issue in my opinion.

Originally we design the single phase elevator since we told the owner you don't have 3ph power. But eventually, the owner bought and install the wrong 3ph elevator with larger horsepower without informing us and want us to fix the issues😂😂
 
kwired said:
Why the need for the 240-208 transformer, motor data says the motor is rated 200 230/460?
That transformer just puts more impedance in the supply line which will be at it's worst during motor starting.

I also agree that using a VFD to drive this motor and to do the phase conversion is likely the best route to use. Even if you wanted to run the motor @ 208 volts the drive could be set to do so.
Click to expand...
The 200V motor and 230/460V motor are different model as indicated in the spec. The one bought is 200V model. The building electrical service is 120/240V 1ph. And voltage output of the phase converter is 240V 3ph.
 
Did the elevator tech describe _when_ excessive voltage drop occurs? Is the problem right at starting (when the elevator motor is in wye) or after the transition from wye to delta?

My hunch is that you might have a system reasonably sized for starting and running the motor but it can't handle the wye to delta transition. But I don't have any experience with wye-delta motor starting.

-Jonathan
 
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