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#128447 - 03/19/03 12:35 AM start up current inrush
payday Offline
Junior Member

Registered: 03/19/03
Posts: 1
Loc: u.k.
Can anyone tell me what the startup inrush current of a 400w lowbay metal halide would be running on 240v.

I've been trying to find this out for a while.

#128448 - 03/19/03 02:58 AM Re: start up current inrush
Joe Tedesco Offline

Registered: 10/07/00
Posts: 3324
Loc: Boston, Massachusetts USA
Try this, I didn't look through the pages for the specific answer to your question, but felt that this information would be helpful.

Perhaps someone will have the time today to review the mateial here.
Joe Tedesco, NEC Consultant

#128449 - 03/19/03 06:09 AM Re: start up current inrush
sabrown Offline

Registered: 12/12/02
Posts: 294
Loc: Ogden, Utah, USA
In looking at Lithonia's Metal Halide 480 VAC Ballast Data the starting current ranges from .4 to .85 amps depending on the ballast with an operating current of 1 amp. I will have to look at the above paper mentioned by Joe to see if there is any difference with an in-rush figure as in-rush could be significantly different and you probably already know the figures I gave above.

#128450 - 03/21/03 02:01 AM Re: start up current inrush
Scott35 Offline

Broom Pusher and

Registered: 10/19/00
Posts: 2722
Loc: Anaheim, CA. USA
Transient Inrush on most Reactive devices like these Ballasts would range from 400% of rated high-end current, to as much as 1000% of high-end current. Time frame would be maybe for only 10-20 cycles for highest draw, tapering down to like 200-300% by the time a full 60 cycles has passed.
I need to check into this and verify data, but it "seems" this would be accurate.

The use of Inverse Time Trip Breakers or Time Delay Fuses is important here.
MCCB with the notation of "HID" usage have this characteristic, plus offer "Switch" duty and designed to deal with quenching a more stable arc, from opening HID Ballasts' circuits during operation.
I'll paste some data regarding HID duty MCCBs later.

Basically, the inrush should not normally trip a properly designed circuit - unless there is component failure or some Ballasts are Resonating the circuit big time (Capacitors mix-matched or incorrectly connected to Reactor Core/Coils, causing hard starts), or there are simply way too many Ballasts on a circuit.

Keep circuits from being max'd out, plus compensate for long circuit runs by upsizing conductors.

Another concern is bouncing harmonics around a 4 wire wye multiwire circuit, where ØA, ØB and ØC have an odd number of different type HID Ballasts. Could result in very wierd initial inrush levels.

Let me verify all this stuff first, then get back with conclusions.

If you are looking for Highest Starting Current / Highest Load Current for the Ballast, this is totally different than what has been listed above!

Ballast for a normal "Probe-Start" M59 Lamp (400 watt Metal Halide Probe Start Lamp) would be a common Constant Wattage Autotransformer configuration (CWA). These have an almost unchanged input line current level from when the arc is first struck across the tube (starting), to driving a stable lamp's full output (running).

Input KVA is adjusted to fit per available voltage levels (within a small tolerance, usually within 10% +/-).

For an ANSI M59 driven by a properly connected and functioning CWA Ballast, the high line current at 240 VAC would be 2.0 Amperes - unless the circuit's power factor is offset (shorted capacitor), then would be more in the 4.0 or higher range!

Properly functioning Ballast would have an apx. power factor of 0.8334 (83.34%), or simply one Ampere per 100 watts, per 120 VAC

(400 watt lamp @ 120 VAC: 4 amps, 400 watt lamp @ 480 VAC: 1 amp, 250 watt lamp @ 120 VAC: 2.5 amps, 250 watt lamp @ 240 VAC: 1.25 amps).

That above example is not universal to all HID Ballasts, only a "Ball-Park" figure for CWA Ballasts.

If the lamp is a 'Pulse Start" type ANSI M135 Metal Halide, the high end current should be the same - 2.0 amps @ 240 VAC.

Hope this helps!!!

Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

#128451 - 03/21/03 02:07 AM Re: start up current inrush
Scott35 Offline

Broom Pusher and

Registered: 10/19/00
Posts: 2722
Loc: Anaheim, CA. USA
Here's the Schematic for a CWA Ballast, which should be the one used to drive your M59 Lamp (400 watt Metal Halide Lamp):

If different than what is in your fixture(s), please let us know!

Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!


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