Rockwell Automation Low-Voltage Switchgear and Controlgear - Manual (Page 15)

mum number of luminescent tubes (including series devices) that can be operated via a single
protective switch.
Lamp type,
(switch) Making
current
peaks
Startup
time
[min]
Starting
current
cos φ Calculation
basis for I
e
Incandescent lamps 15 · I
e
- - 1 ≤ I
eAC-5b
Halogen lamps
- Transformer operation
- ECG
1
operation 10 · I
e
- - 0.95
see Section1.4
≤ 0.7 · I
eAC-3
Luminescent lamps
(choke operation)
- uncompensated
- parallel compensated
- DUO circuit
≈ 2 · I
e
≈ 20 · I
e
≈ 2 · I
e
-
-
- -
-
- 0.5
0.9
0.9
≤ I
eAC-5a
≤ I
eAC-1
, ≤ I
eAC-6b
≤ I
eAC-1
Luminescent lamps
- ECG
1
) operation, AC 10 · I
e
- - 0.9
≤ 0.7 · I
eAC-3
Mercury vapor high
pressure lamps
- uncompensated
- parallel-compensated
≈ 2 · I
e
≈ 20 · I
e
3 – 5
3 – 5 ≈ 2 · I
e
≈ 2 · I
e
0.4 – 0.6
0.9
≤ 0.5 · I
eAC-1
≤ 0.5 · I
eAC-1
, ≤ I
eAC-6b
Halogen metal vapor
lamps
- uncompensated
- parallel-compensated
≈ 2 · I
e
≈ 20 · I
e
5 – 10
5 – 10 ≈ 2 · I
e
≈ 2 · I
e
0.4 – 0.5
0.9
≤ 0.5 · I
eAC-1
≤ 0.5 · I
eAC-1
, ≤ I
eAC-6b
Sodium vapor high
pressure lamps
- uncompensated
- parallel-compensated
≈ 2 · I
e
≈ 20 · I
e
5 – 10
5 – 10 ≈ 2 · I
e
≈ 2 · I
e
0.4 – 0.5
0.9
≤ 0.5 · I
eAC-1
≤ 0.5 · I
eAC-1
, ≤ I
eAC-6b
Dual-source lamps ≈ 1.3 · I
e
≈ 3 ≈ 1.3 · I
e
1 ≤ 0.9 · I
eAC-1
Tab. 1.3-1
Making currents for lamps and notes on selecting switchgear
1
) ECG … Electronic control gear
1.4 Transformers
If a low-voltage transformer is switched on, there is a short-term current surge (rush). The peak
surge currents evoked by field set-up can be up to 30 times greater than the transformer rated
current. The inrush currents vary according to the transformer type. They depend on the
position of the coil, the characteristics of the magnetic circuit and especially on the phase angle
of the voltage during switching on. The switchgear must have a correspondingly high making
capacity in order to avoid contact welding.
IEC 60947-4-1 provides the utilization category AC-6a for switching transformers. The permitted
rated operational current I
eT
(AC-6a) for switching transformers with a making rush factor of ≤ 30
can be determined as per IEC 60947-4-1 (Tab.7b) from the data of the AC-3 switching capacity:
I
eT30
= 0.45 · I
eAC-3
for n ≤ 30
n = peak value of the making current/peak value of the rated operational current
In the case of larger rush factors the following applies:
I
eTn
= I
eT30
· 30/n
The factor «n» should be specified by the transformer supplier. If no specifications are available,
the following guideline values apply for «n»:
LVSAM-WP001A-EN-P - April 2009 1-5