PSCT-75 datasheet(23/44 Pages) ABB

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Spare parts contactors

Classic products

1000

100

(V)

T (s)

1000

100

Surge suppressors for contactor coils

Description

The operation of inductive circuits causes overvoltages, in particular on opening of the contactor coil.

The electromagnetic energy stored in the coil during contactor closing is restored on opening in the form of

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-

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.

k =

in DC: k =

or in AC: k =

Ûc

Uc√2

3500

For example the following is obtained for the above graph: k =

≈ 60

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

For contactors

Rated control circuit

voltage

Type

Order code

Pkg

qty

Weight

(1 pce)

AC DC

EH175 ... EH300, EK100 ... EK210

24...48

●

–

RC-EH300/48

SK829007-A

0.015

110...415

●

–

RC-EH300/416

SK829007-B

0.015

EHDB130 ... EHDB360

110...415

–

●

RC-EH300/415

SK829007-B

0.015

EH370 ... EH800, EK370 ... EK550

48...100

●

–

RC-EH800/110

SK829007-C

0.015

EHDB520 ... EHDB960

–

●

EH175 ... EH800, EK110 ... EK550

24...125

–

●

EH370 ... EH800, EK370 ... EK1000

220...600

●

–

RC-EH800/600

SK829007-D

0.015

EHDB520 ... EHDB960

–

●

PSCT-75 Datenblatt(PDF) 23 Page - ABB

PSCT-75 Datenblatt(HTML) 23 Page - ABB

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