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

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wyreman

wyreman

Senior Member
Location
SF CA USA
Occupation
electrical contractor
Sure that was the first measurement
212v on nominal 208v drops to
194v at entrance on inrush

194/208=%/100

= -6.73% typical at Srvc conductors
Poco measured different =)

Very similar #s at elevator room

Still vd could be for the first reason
W soft start configured wrong
Great
Easy fix (by others)

Or
Too small Xfmr. Expensive
Or
$rvc conductors ($mall pipe)
Or
Loose nuts at the origin
Possible but
Only for big 3phase load? Goose chase
 
H

Haji

Banned
Location
India
If the service conductors are too small, they would be heated up along their entire length at the end of full day operation of the elevator. Have you checked it up? Are the conductors insulation a bit too warm to touch?
 
H

Haji

Banned
Location
India
To rule out any maloperation of soft starter:Is the lights dimmìng present only during starting of elevator or throughout the elevator operation?
 
H

Haji

Banned
Location
India
wyreman said:
Sure that was the first measurement 212v on nominal 208v drops to 194v at entrance on inrush 194/208=%/100= -6.73% typical at Srvc conductors Poco measured different =)Very similar #s at elevator roomStill vd could be for the first reason W soft start configured wrong GreatEasy fix (by others)OrToo small Xfmr. Expensive Or$rvc conductors ($mall pipe)OrLoose nuts at the origin Possible butOnly for big 3phase load? Goose chase
Click to expand...
One more solution option:In the elevator motor starting current, there is a large reactive current component and if a thyristor controlled capacitor is used to compensate it, voltage drop could be reduced and light dimming problem solved.
 
wyreman

wyreman

Senior Member
Location
SF CA USA
Occupation
electrical contractor
wyreman said:
View attachment 13541
It was just green tagged about 5 yrs ago so the 600a Srvc should be sized right
It's a 120/208 3p 4w

Waiting for poco log of brown outs and will ask mapping Dist to Xfmr
The voltage is steady except for each and every time elevator starts Going up
Click to expand...

Wow, a capacitor! What a great idea!
If the soft start is not it and
other Srvc issues too hard to fix,
what an Excellant idea?
 
T

topgone

Senior Member
wyreman said:
Wow, a capacitor! What a great idea!
If the soft start is not it and
other Srvc issues too hard to fix,
what an Excellant idea?
Click to expand...
Be careful with entertaining that idea. There should be no capacitors installed near softstarter units or even at the motor terminals. If capacitors will have to be installed at the softstarter input side, place those capacitors as far upstream from your softstarter unit/s. You will destroy your softstarter's SCRs if a capacitor in very near your unit.
 
Jraef

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
topgone said:
Be careful with entertaining that idea. There should be no capacitors installed near softstarter units or even at the motor terminals. If capacitors will have to be installed at the softstarter input side, place those capacitors as far upstream from your softstarter unit/s. You will destroy your softstarter's SCRs if a capacitor in very near your unit.
Click to expand...
Sage advice. If your capacitors are for running power factor correction, you can (should) isolate them off-line while the soft starter is ramping them add them when running. That however does nothing for you with regard to voltage dip at start-up. Trying to accomplish Capacitor Assisted Starting is tricky at best, and never someting I would recommend using when any kind of solid state equipment is involved.

wyreman, did you try the soft starter settings I suggested yet?
 
wyreman

wyreman

Senior Member
Location
SF CA USA
Occupation
electrical contractor
Going there today or tomrw
To check all else
Conference call with Otis Tuesday or Wednesday

I could download the manual and just
Review the ramp and current limiting settings Menu
As configured now
Before the call
 
wyreman

wyreman

Senior Member
Location
SF CA USA
Occupation
electrical contractor
Going there today or tomrw
To check all else
Conference call with Otis Tuesday or Wednesday

I could download the manual and just
Review the ramp and current limiting settings Menu
As configured now
Before the call
 
wyreman

wyreman

Senior Member
Location
SF CA USA
Occupation
electrical contractor
I'm actually wondering
If the poco
Size this Xfmr image.jpg for 400 A
Because the underground lateral pipe run
Is a single pie
When their own specs
Call for parallel conductors
For 600 A
 
H

Haji

Banned
Location
India
Beware it may be a double or triple whammy: in addition to service conductors being too small, POCO service transformer too small or loose connections or all together may also be present.
 
Jraef

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
About 20 years ago I did a pump station out in Tracy that had 2 big soft starters on it, totaling 500HP. The service was supposed to be 1000A, 480V. I thought the pad mount transformer looked too small, but you can't see anything from the outside, just the physical size. Nothing I could do would allow the soft starters to start without a severe voltage drop that all of the nearby residences noticed. After months of denial by PG&E about the transformer size, finally one day the power failed and I traced it to being a connection or fuse inside of the transformer cabinet, so PG&E had to come out. When their tech opened it up, the terminal had melted off. I was standing right there when he opened it and saw the nameplate saying it was a 500kVA transformer. I told him there was no way, even under utility rules, that a 500kVA transformer could provide a 1000A service. He refused to accept it and reconnected the transformer. When I started the pumps and he saw the VD, he called an engineer at PG&E, who continued to deny anything was wrong. Only when he actually came out and saw it did he realize they had put in a 500kVA transformer when it was supposed to have been a 1500kVA. Deny, deny, deny... That's their way, so be ready for that.
 
wyreman

wyreman

Senior Member
Location
SF CA USA
Occupation
electrical contractor
Finally met with Otis and the current was set to
185% we move that to 250% of fla
Result : voltage dropped lower from
193 to 185 out of 208 nominal


Can't find the parameter to change the length of ramp time

There's an on delay
Which I don't understand what that means
Also off delay both set to zero

That's the ramp time which were trying to minimize but it doesn't seem to say that in the enclosed spec
 
wyreman

wyreman

Senior Member
Location
SF CA USA
Occupation
electrical contractor
image.jpg

We couldn't find anything in the parameters menu that would allow you to change the ramp up time.
The delay is just how long the pump is delayed on or off after the motors

Couldn't find the time


Looks like those empty pipes in the meter cabinet where there for a reason.
Poco wire is undersize although they do deny it
 
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