xfmr stiff enough... Elevator soft starts - lights dim

[wyreman]

If all three phases behave the same with resistance test, then I would suspect the load. The motor looks quite classic. Have you done AC resistance test on all the windings? You apply a few volts at 60 Hz on each winding and test the amps and verify that no one winding stands out.

How do you do an AC resistance test? ??? I have an old variac but I don't want to get in the elevator cabinet... too much
Plus I'd really have to think what I would do with it - just hook it up as a star or a wye and let a few volts flow while measuring the current... I don't think Otis would be happy

I have a fluke 289, that should be, ohm, ok enough at the uv&w terminals, dont you think? its got a bunch of AA's in it

 

[wyreman]

 

[wyreman]

required minimums
http://www.pge.com/tariffs/tm2/pdf/ELEC_RULES_2.pdf

 

[Electric-Light]

Nearly zero to 300A is quite the load step and your interpretation of 95% floor conditions do not extend to motor starting conditions. See the last sentence in the first paragraph. Changing the ramp rate won't change the amount of drop but can change the visual disturbance.

http://www.pge.com/includes/docs/pd...ergystatus/powerquality/voltage_tolerance.pdf

I would say the L1-N, L2-N, L3-N light bulb is the first thing to check. It's quite unlikely that loose connection is equally loose on all connections.
For practical purposes, light bulbs are faster than test equipment except for power quality test equipment. This mostly has to do with transfer function in converting the electrical fluctuation to something we can sense.

Once you identify it, you use the load bank. Measure the voltage as close as possible to the utility side and not at the load cable, So if L1 is 120v no load and 117v at 30A, that's 0.1v/A. If one phase has significantly more drop than the rest and it is consistently with the previous 3-bulb test, I would say supply side. If you get more or less the same drop on each phase, then I would say its sagging due to heavily biased loading and I think this is what the PoCo is suggesting. Something you would be able to see right away if you rent a proper three phase instrument. This is just like the mechanical analogous. You're sagging. You have a defective suspension or your load is horribly uneven.

How do you do an AC resistance test? ??? I have an old variac but I don't want to get in the elevator cabinet... too much

Good point. The DC ohm is next to just about zero for a 50 hp 200v motor, so you have to use a motor winding test equipment.

No I didn't bother as each time the problem was found before the meter.

I am not saying the problem isn't on their end but don't jump the gun yet. It could be due to excess connection resistance on their stuff or it could be load conditions causing excess unbalanced load.

Your charts are too tiny to see.

 

[wyreman]

yes on the powersight logs I posted it looks like the current is unbalanced during runtime - i'll have to clamp that side next time with the small wires and compare min max flow to the three legs

 

[wyreman]

heres maybe a better view at the powersight charts,
its not a real proper power quality meter, just a data logger - and kind of old too....

https://1drv.ms/f/s!AkuU8mYuf3eEf0nElde4MKltTXw

its just because of the slow sampling rate , the quickest is every 1 second!

i really have to go back and get better Elevator min max reading with a finer grain of detail
individual reading on the parallel conductors

you can see the amps vary from 314 / 342 /333
while the volts show 185/ 190 / 197
but that is due to the sampling interval of 1sec...

I should be able to prove its on their side of the line-
prove that my load is balanced
- by showing good balanced or bad rickety instantaneous amp draw and voltage sag with a 100kW load bank at the mains [i'll use both the data logger and some clamp meters]
but its $500-$1000 to rent it for a day

- by showing bad inferred voltage at the mains with small [30a] load and precise volt measure
That's just not as convincing]

what will the 3 lightbulb test actually prove?
helps narrow it down to one leg
If all legs dip down -that much... in the same moment - then it must be their problem because there is no imbalance

I know the voltage sags and the lights dim when the elevator rises
The only convincing way is to
not use the elevator and pull a big balanced load on the line conductors -
I have just been avoiding the obvious expense of renting the load bank because it seems so obvious to me that it must be their problem because its on their side of the meter and my load cant be that out of whack

-

 

[mbrooke]

What is the voltage, at the service, at light load/no load between L-G and L-L across all the phases?

 

[gar]

170223-0846 EST

wyreman:

Several points.

Electric-Light's suggestion of connecting three light bulbs to the circuit is very useful and virtually no cost. Bulbs are too bright to look directly at so use the lowest wattage you can get. 15 W might be appropriate.

From the information you have provided your power system, PG&E, source is three single phase transformers connected as a wye secondary. We don't know how the primaries are connected. Each transformer is now 100 kva with a secondary voltage of 120 V. Thus, current rating is about 800 A. If you assumed a 3% impedance transformer, then the approximate transformer voltage drop at full load is 120*0.03 = 3.6 V (800 A).

When I run a quick test with a 15 W bulb on 120 V with a 2.2 V change I notice a small flicker, not objectionable.

Because you have a wye source you should be measuring the line to neutral voltages instead of line to line voltages. This will more directly point you to the single line that is your biggest problem.

You are measuring line current, and that is also the transformer secondary current.

When you connect your logger to measure voltage line to neutral we can fairly easily estimate the source impedance as seen at the meter point back toward PG&E. My rough guess at this time from your data is about 4.5 V (when translated to 120 V base) at 100 A or 0.045 ohms. This includes all PG&E primary impedance, transformer impedance, and the line and neutral from the transformer to the meter. At 800 A this would be a voltage drop of 36 V out of 120 or 30%, at 300 A, your approximate peak, 30*3/8 = 11%.

It would appear that you get very short 300 A current pulses, but not at the start of every 100 A pulse, and the more steady current pulse is about 100 A.

From your previous comments one of the PG&E source lines has a greater voltage drop than the other two, but there does not appear to be more than about a 2 to 1 ratio difference. I am not using the word phase here because it is hard to know what it means. For example you are measuring a line current and associating that with a line-to-line voltage which are not directly related together.

Knowing what the wires are from the transformers to the meter and the distance you can estimate resistance and and expected voltage drop for a given current.

Change your logger voltage connections and provide some new plots.

You do not need to buy or rent other equipment at this time. It is providing useful information.

The 300 A short pulses are some sort of inrush that is random in occurrence. Not all 100 A pulses have a 300 A pulse. What do the 5 100 A pulses represent? There are always 5 that occur equally spaced in time over about 1 minute.

.

 

[Ingenieur]

sorry, :ashamed::dunce:
does that mean that two conductors are better than one, even tho one is big and one is small?
:ashamed::slaphead:

yes
if it was the same size 50% Vdrop reduction
since it is only 1/2 the originals size only 1/3 less Vdrop (10 vs 6.7 in my example)
but still an improvement

what are your actual cable sizes?

 

[Ingenieur]

Ingineur, I Googled the controller. It's like a three phase ceiling fan speed controller with a computer controlled slider. Upon reaching full speed, it gives "ready" signal at which point the elevator controller opens ascend valve.

Have you done the three light bulb test?
You connect a filament light bulb (28 or 40W) L-N on each phase. Three of them lined up, side by side simultaneously. This is still the best way to prove flicker complaint unless you have a THREE PHASE instrument with flicker test capability. If this doesn't pass, you have to see if it's line or load side
Light bulbs are in sync and you are watching to see if one bulb flickers significantly more than the other two.
An array of three single phase meters are not in sync and digit readouts are not appropriate for this kind of test on their own

If you have a 4 3/4 digit meter like 289, you could apply a 20A heater L-N on each phase one at a time and compare loaded vs unloaded and expand and it would be a good way of narrowing down suspected loose phase connection. 2.22v drop at 20A = 22.2v at 200A. A loose connection likely won't coincide to the same drop on all three phases. The test load is selected to balance between getting good enough readability and ease of handling. 2A on a 200A circuit likely won't produce strong enough signal.

If all three phases behave the same with resistance test, then I would suspect the load. The motor looks quite classic. Have you done AC resistance test on all the windings? You apply a few volts at 60 Hz on each winding and test the amps and verify that no one winding stands out.

could you please post the link to the controller?

thanks

 

[Bugman1400]

Did the POCO ever do a Flicker Study? If so, please post results. Also, please post source impedance (r+jX) from POCO of service delivery point at delivery voltage base.

 

[mbrooke]

Did the POCO ever do a Flicker Study? If so, please post results. Also, please post source impedance (r+jX) from POCO of service delivery point at delivery voltage base.

Now your talking! :happyyes:

 

[wyreman]

going back tuesday, God willing I'll post new findings then.
Also will get an email out to poco hopefully today thx guys!

 

[mbrooke]

This might help:

https://www.powermonitors.com/download/file/WP61

I do not have the PDF, but if anyone does I think it is a good anchor to measure up against.

 

[gar]

170224-2130 EST

I don't think that wyreman needs much more test equipment than what he already has. But his logger voltage measurement does need to be connected line to neutral.

There does appear to be a moderate difference in line current between the three phases. May or may not be important. Could be a result of the difference in source impedances of the three phases. When you make use of the data from the about 100 A pulses the pulse duration is long enough that you can estimate the source impedance of each phase. With a useful min-max current meter you can probably catch the peak value of the shorter transients, I believe wyreman has done this.

I would like to know how or why this elevator produces the group of 5 about 100 A pulses. Are these 5 starts and stops of the elevator or something else? Is the load simply an induction motor with an electromechanical contactor or something else?

.

 

[Ingenieur]

What type of driving machine? Traction? Etc
under what conditions does it happen?
ascending loaded
ascending unloaded
descending
etc
accel or decel

has fla under worse case been measured and compared against nameplate?
have rate of accel and decel been measured/adjusted?

 

[Electric-Light]

http://www.aesupply.com/pdf/Class72G_Instruction Guide1_01_21_20053-3.pdf
Controller manual. It can be wired for in-line but the given the size and voltage it looks like in-Delta as Jraef commented.

Ingineur, according to that manual it implies he's talking about hydraulic

If close to half your load is one large motor....then you are going to experience a voltage dip on starting.

There's really no escaping relative size effect. One seat for adult is one seat but there is nothing you can do to expect a six person personal craft to have the same steadiness as one of those Vancouver Island ferries when you jump around on it. Relatively speaking the 0 to 300A is huge for the size of transformer. If each circuit was a branch, the service size is like a set of seats setup for your party. The entire watercraft(transformer and the service it is supported) dictates stability. You could talk all day about how you can jump around on the ferry and feel like you're on a slab of concrete but nothing you can do to get the same stability on a small boat.

Single ended service from a small(load or service vs transformer size) transformer is the least stiffest compared to a large multi-point with multi-point feed.

 

[wyreman]

170224-2130 EST
...

I would like to know how or why this elevator produces the group of 5 about 100 A pulses. Are these 5 starts and stops of the elevator or something else? Is the load simply an induction motor with an electromechanical contactor or something else?

.

I assumed the five pulses are the result of
going over to the garage elevator door and pushing the buttons for all 5 floors.
the elevator goes up, unloaded, stops doors open and close, and then it moves to the next floor,

but now that you mention it, i think these are one second intervals... it must take at least twenty seconds - prob more- for the elevator to do its business at each floor.

one more thing to check!

 

[wyreman]

What type of driving machine? Traction? Etc
under what conditions does it happen?
has fla under worse case been measured and compared against nameplate?
have rate of accel and decel been measured/adjusted?
#unknown

What type of driving machine? Traction? Etc
#not checked
under what conditions does it happen?
#ascending --- every time


has fla under worse case been measured and compared against nameplate?
#yes --- as expected

have rate of accel and decel been measured/adjusted?
#unknown

 

[wyreman]

the uploaded photos are all too small
this may work better

photo album
https://1drv.ms/f/s!AkuU8mYuf3eEaUawuT2w6biKbG4




http://reliableplant.com/Read/4288/motor-defects-fault-zone