Lights blink every time a motor starts

[hillbilly1]

Five homes is no problem, neither is fifteen if the system is built correctly. :smile:

That was the problem, when the system was originally built, the transformer was sufficient, as more and more loads were added the system was not upgraded. Wired a store that originally had a 400 amp service, the load had grown to 380 amps per leg on the service with the voltage dropping down to a constant 105 volts during peak load, POCO had 4/0 AL service lateral at 200'
Upgraded service to 1200 amp, POCO wanted to install (2)-4/0 service laterals. Load was also being increased due to doubling the size of the store. Met with the engineers and explained the problem they were causing, and they agreed to upgrade to parallel 350 Kcmil and also upgrade transformer size. Voltage now at acceptable levels.

 

[charlie]

. . . Met with the engineers and explained the problem they were causing. . .

Calling and talking with the serving electric utility is key to getting the results you need. Sometimes it doesn't work but most of the time a meeting will work wonders. :smile:

 

[weressl]

Okay........
Exactly how much difference would it make to the voltage dip transient as the motor is started?

Did you run the study or not?

 

[Besoeker]

Did you run the study or not?

You suggested it. Did you run the study?
Anyway, the calculations are quite straightforward.
Why would I need a modelling programme?

But if you want calculations based on your 5kVA transformer, the 3.5kW of heating and lighting and the 2 HP motor, here's where it's at.
You first have to make some assumptions about the motor starting current.
I took it to be six times FLC at a pf of 0.3.
I also assumed a 220V supply but, in percentage terms, that's irrelevant.

So, on that basis, starting the 2HP motor with no other load connected the voltage would drop to 197V
With every other thing connected it would drop to about 196V.

Sure, it IS a difference.
In post #13 I should have said it won't make much difference.
My bad.

 

[weressl]

You suggested it. Did you run the study?
Anyway, the calculations are quite straightforward.
Why would I need a modelling programme?

But if you want calculations based on your 5kVA transformer, the 3.5kW of heating and lighting and the 2 HP motor, here's where it's at.
You first have to make some assumptions about the motor starting current.
I took it to be six times FLC at a pf of 0.3.
I also assumed a 220V supply but, in percentage terms, that's irrelevant.

So, on that basis, starting the 2HP motor with no other load connected the voltage would drop to 197V
With every other thing connected it would drop to about 196V.

Sure, it IS a difference.
In post #13 I should have said it won't make much difference.
My bad.

What is the transformer impedance and what are the supply characteristics?

 

[cschmid]

I agree this is a POCO issue and it could be distance voltage drop as it is the secondary side and their wires are also prone to voltage drop..connection problems would also be a check..I have found no problem dealing with the poco's on issues like this..all you need is some recorder info as to voltage and amperage..and normally you can get poco to put in the recorder to record it..

 

[quogueelectric]

If you have load modeling program you can demonstrate it to yourself.

Try a 5kVA transformer.
Now add about 15-100W lighting load,
Now add a 3kW electric stove,
Now start a 2 HP motor on it and see the voltage stability at each point.

Reverse the order.

It is really elementary.

Come on now throw him some internal xformer impedance and maimum power transfer formulas to really peak his interest.:smile:

 

[DanZ]

Uhm, if it's only one light, or most noticeable on one light, wouldn't it make sense to see what was wrong with that light? Sorry if you already have checked that fixture, but I didn't see it mentioned anywhere.

Is the lamp itself tight, is the fixture wired properly and tightly, is the lamp holder in good working order, is it a defective lamp, is it a CFL, are the connections in the panel tight, do the wires meg properly, etc.

I know it's odd, and a long shot, but I have had loose linear fluorescent lamps (don't ask), dead or dying lamps, loose connections, a cracked lamp holder and bad wires cause flicker problems when loads were placed on a circuit.

 

[Besoeker]

What is the transformer impedance and what are the supply characteristics?

Impedance (ohms) 0.484
Resistance (ohms) 0.11616
Reactance (ohms) 0.46948

 

[ssimpson]

similiar problem

similiar problem

I had have had a similiar problem and had poco use recording meter and check all connections there is another residence on the xfmr with no problem poco said voltage drop was within spec's. Customer not satisfied.