SEAL 44/62 Ultra Plus Spécifications télécharger pdf (Page 23)

580 Eastview Drive Laurel, MS 29443 (800.956.3456)

www.HowardLightingProducts.com

Reignition Phenomenon

HPS and other HID lamps actually turn ON and OFF 120 times per second. Current is cut off for a millisecond

or so at each midpoint, or zero crossing point, of the AC 60 Hertz cycle (Figure 15A). The lamp stays hot

enough to automatically restrike after this very, very short outage. However, if several cycles of the AC power

are lost or drop out due to loose wire connections or shorts, the lamp cools sufficiently to turn OFF and will not

restrike immediately (Figure 15B).

To avoid dropouts due to poor connections, do not pull the wires tight when installing the luminaire or its inter-

nal components such as the ballast, photocontrol, starter or capacitor. The lamp must be screwed into the

socket properly to make a good connection. The coil spring must be compressed completely to

make proper contact at the base of the socket. All of the metal on the lamp’s screw base should be hidden

below the rim of the socket when the lamp is screwed in completely.

The lamp socket center contact and the tip of the lamp base must be in proper contact when the lamp is in-

stalled. If the center contact and lamp tip become misaligned due to a mismatch between the socket contact

and the lamp tip, the lamp may not start due to poor or partial contact between the two. If this problem occurs,

some service technicians may try turning the lamp out 1/2 turn or so. In some cases, the lamp may now light,

but this is not an acceptable solution to the problem. The connection between the lamp and socket is not un-

der full spring pressure, and electrical arcing will occur, drastically reducing lamp life or resulting in socket

burnout.

Vibration Sensitivity

HPS lamps nearing the end of their service lives are very vibration sensitive. Vibration causes a rise in lamp

current above the end-of-life voltage. HPS light color gives a good indication of relative lamp age. Older HPS

lamps give off a whiter light. The color rendition they produce actually is better than new HPS lamps.

Vibration in the lamp due to wind or traffic can cause the lamp to cycle. Vibration-induced cycling is common in

fixtures mounted on bridges. You can simulate this vibration in a burning lamp by striking the mounting pole

with a short length of lumber, or by actually bumping the light fixture or light bulb with your hand. If the lamp

turns OFF when the pole is struck, it is probably vibration sensitive.

The bump test also is a good way to check for intermittent open circuits and poor connections in the lamp and

fixture.

Figure15. (A) Voltage actually is cut to

the lamp every time alternating current

changes direction. This happens 120

times per second with 60 Hertz

AC power.

(B) When several cycles of AC current

drop out or are lost, the lamp with

turn OFF

Page 23

1 2 ... 18 19 20 21 22 23 24 25 26 27 28 ... 39 40

Pas de commentaire

SEAL 44/62 Ultra Plus Spécifications Page 23