Load Current Influence - ABB i-bus KNX Product Manual

®
ABB i-bus KNX
4.1.1

Load current influence

© 2008 ABB STOTZ-KONTAKT GmbH
Planning and application
The electronic ballast is a device for operating gas discharge lamps, e.g.
fluorescent lamps. During normal operation the electronic ballast converts
the mains voltage to an optimum operating voltage for the gas discharge
lamps.
With the original choke/starter circuitry the lamps switched on consecutively,
with the electronic ballast all fluorescent lamps switch on practically
simultaneously. If switch on occurs at the mains voltage peak, the buffer
capacitor of the electronic ballast cause a high but very short current pulse.
With the use of several ballasts on the same circuit, the simultaneous
charging of the capacitors may result in very large system switch on currents
(inrush current peaks I ) flowing.
p
This peak inrush current I
contacts as well as by the selection of the respective circuit protection.
In the following the effects of the electronic ballast peak inrush current
and the associated limitation of the number of electronic ballasts in the
Switch/Dim Actuators are examined.
The inrush current of the electronic ballast depends not only on the power
consumption but also on the type, the number of elements (lamps) and on
the manufacturer. For this reason the given maximum number of connectible
electronic ballasts per output can only relate to a defined type of electronic
ballast. For a different type this value can only represent an estimation.
In order to properly estimate the number of electronic ballasts, the peak
inrush current I with the respective pulse width of the electronic ballast
p
must be known.
In the meantime, these values are stated by the manufacturer in
the technical data or are available on request.
Typical values for single element electronic ballasts with T5/T8 lamps are:
Peak inrush current 15 A to 50 A with a pulse time of 120 μs to 200 μs.
Every relay in the output of the Light Controller features the following
maximum switch on values:
Maximum peak inrush-current I
Maximum peak inrush-current I
Maximum peak inrush-current I
If these limit values are exceeded the relay will be destroyed, e.g. it will weld.
Example
ABB EVG 1 x 58 CF:
Peak inrush current Ip = 33.9 A (147.1.μs)
For the LR/S 4.16.1 Light Controller this means:
Maximum number of electronic ballast per output = 400 A / 34 A = 11
electronic ballasts
is to be considered when designing the switch
p
LR/S x.16.1
(150 μs)
400 A
P
(250 μs) 320 A
P
(600 μs) 200 A
P
102