Page 23 - Spare-part-for-contactor

Spare parts contactors
Classic products

(V) Surge suppressors for contactor coils 1
1000
T (s) Description
0
100 The operation of inductive circuits causes overvoltages, in particular on opening of the contactor coil.

1000 The electromagnetic energy stored in the coil during contactor closing is restored on opening in the form of
0 100 surges, the slope and amplitude of which may rise to several kilovolts. A number of drawbacks are observed
ranging from interference on the electronic devices to breakdown of insulators and even destruction of cer-
A884D tain sensitive components.
The graph opposite reproduces the oscillogram showing voltage discharges at the terminals of a 42 V / 50 Hz
coil without peak clipping. The coil was switched by 8 series-connected poles of a contactor relay.

Following a burst of discharges with a very steep slope a damped oscillation emerges with a peak value of
3500 V.

Overvoltage Factor
The overvoltage factor k is defined as the ratio of the maximum overvoltage peak value Ûs to the peak value
Ûc of the coil rated control voltage Uc:

= Ûs max. in DC: k = Ûs max. o r in AC: k = Ûs max.
k
Ûc Uc Uc√2

For example the following is obtained for the above k = 3500 ≈ 60
graph:
42 √2

To reduce the harmful effects of these overvoltages, ABB has developed a range of surge suppressors de-
signed to reduce the k factor defined above and to limit or even completely eliminate the high pre-damping
voltage frequencies.

Each case is different, but the technical data tolerances and the generous sizing of parts have enabled us to
reduce the number of variants.

We have chosen the following solutions: transil diodes, varistors and RC blocks.

Note: A varistor is a resistor whose value decreases to a very large extent when a certain voltage is applied
at its terminals.

Ordering details Rated control circuit Type Order code Pkg Weight
voltage qty
For contactors Uc SK829007-A
SK829007-B (1 pce)
EH175 ... EH300, EK100 ... EK210 V AC DC SK829007-B kg
24...48 ● – RC-EH300/48 SK829007-C 2 0.015
EHDB130 ... EHDB360 2 0.015
EH370 ... EH800, EK370 ... EK550 110...415 ● – RC-EH300/416 SK829007-D 0.015
EHDB520 ... EHDB960 2 0.015
EH175 ... EH800, EK110 ... EK550 110...415 – ● RC-EH300/415
EH370 ... EH800, EK370 ... EK1000 2 0.015
EHDB520 ... EHDB960 48...100 ● – RC-EH800/110
–●

24...125 –●
220...600
● – RC-EH800/600
–●

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