HPS Lighting Load tripping breaker?

[mlagrone]

I have approx. 125 100watt HPS fixtures on a 225 amp 480 volt 3-phase breaker. I am switching a lighting control panel via a contactor. I have about a 145 amp draw across all 3 phases all looks to be normal, however every few days the main sub-feed breaker trips (225 amp 3pole I line breaker...) Someware I have read that the HPS ballasts can draw 20-50X the rated current depending on where it is on the sign wave? has any one heard of this? If this is correct I will need to install a 400amp breaker to prevent this tripping to occur. any advise?

:?

 

[Jraef]

It's called "inrush current" and takes place when the transformers on the front-end of the ballasts are first energized. In that very first instant that the contactor closes, the windings of that transformer are essentially a short circuit. The impedance (resistance to the flow of current) to that inrush is created by the magnetic fields inside of the transformer, but until they are established there is nothing but the natural wire resistance. Depending on the point of the sine wave when the contactor closes and the reaction time of the magnetics, it's true that there can theoretically be a 20X momentary inrush. But we are only talking about fractions of a second; just a few cycles for the magnetic fields to get established. Sometimes however that's enough to trip a breaker or blow a fuse, it all depends. If you increase the size of the breaker you will have to increase the conductor size too. It might be less expensive to split the load between two breakers and use the same conductors with maybe just a new home run for half of the circuit.

 

[jim dungar]

I have approx. 125 100watt HPS fixtures on a 225 amp 480 volt 3-phase breaker. I am switching a lighting control panel via a contactor. I have about a 145 amp draw across all 3 phases all looks to be normal, however every few days the main sub-feed breaker trips (225 amp 3pole I line breaker...) Someware I have read that the HPS ballasts can draw 20-50X the rated current depending on where it is on the sign wave? has any one heard of this? If this is correct I will need to install a 400amp breaker to prevent this tripping to occur. any advise?

:?

20-50X is a bit too much, it is probably more like 15-20x.

However, your problem is the inrush current. Have you checked the adjustable magnetic set point of your breaker (the factory setting is at minimum)?

 

[normbac]

Would it help to have them come on minutes apart per row

 

[ptonsparky]

Yes.

 

[tortuga]

I have approx. 125 100watt HPS fixtures on a 225 amp 480 volt 3-phase breaker. I am switching a lighting control panel via a contactor. I have about a 145 amp draw across all 3 phases all looks to be normal..

Are all 100W lights running off 277V?
Are they all 100W lights? how accurate is the count?
That amp draw seems high for 100W lights on a 277V circuit.
What is the nameplate amps of the 100W HPS ballast?
What are the branch circuits protected at 20,30 or 50A?
What is your voltage drop?
Are you sure all phases are 145A?
Are they on for 3hr or more?
Is the contactor a mechanically held (latching) HID lighting type or is it a magnetically held coil motor control type?

 

[topgone]

20-50X is a bit too much, it is probably more like 15-20x.

However, your problem is the inrush current. Have you checked the adjustable magnetic set point of your breaker (the factory setting is at minimum)?

Agree on the inrush thing. I'd say roughly 30X inrush current is possible. Like what was mentioned, if the breaker has an adjustable magnetic set point, it should turned higher to ride over the inrush.

I see it this way: assuming care had been taken to divide the loads per phase as much as possible equal - (100W X 125)/3 = 4167 watts per phase.
Your line current will be around 4,167/(277 X 0.9PF) = 16.7 amps.
Inrush = 30 X 16.7 = 501 amps, your breaker trips if the magnetic set point was set lower than this. It would be worse if the phase loads are not balanced.

Please refer to the time-current curve of your breaker to avoid nuisance trips.