Page 664 - Motor protection and control Manual motor starters, contactors and overload relays

5/48 ABB MOTOR PROTECTION AND CONTROL

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Surge suppressors for contactor coils

The operation of inductive circuits causes overvoltages, in particular on opening the contactor coil.
(V)
1000 The electromagnetic energy stored in the coil during contactor closing is restored on opening in
T (µs) the form of surges, the slope and amplitude of which may rise to several kilovolts. A number of
0 100
drawbacks are observed ranging from interference on the electronic devices to the breakdown of
1000
insulators and even the destruction of certain sensitive components.
0 100 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
05
peak value Ûc of the coil rated control voltage Uc:
Ûs max. Ûs max. Ûs max.
k = in DC k = in AC k =
Ûc Uc 3500 Uc √2

1SBC101042F0014 For example the following is obtained for the above graph: k = 42 √2 ≈ 60

To reduce the harmful effects of these overvoltages, ABB has developed a range of surge suppres-
RV5 sors designed 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 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.
1SBC101042F0014 For For Rated control circuit Type Order code Pkg Weight

(1 pce)
contactor
voltage - Uc
contactors
qty
RC5-1 relays V AC DC kg
AS, ASL NS, NSL 24...50 ● ● RV5/50 1SBN050010R1000 2 0.015
50...133 ● ● RV5/133 1SBN050010R1001 2 0.015
110...250 ● ● RV5/250 1SBN050010R1002 2 0.015
250...440 ● ● RV5/440 1SBN050010R1003 2 0.015
AS NS 24...50 ● – RC5-1/50 1SBN050100R1000 2 0.012
50...133 ● – – RC5-1/133 1SBN050100R1001 2 2 0.012
1SBC101042F0014 ASL NSL 250...440 ● – ● RC5-1/440 1SBN050100R1003 2 2 0.012
0.012
1SBN050100R1002
110...250
RC5-1/250
●
RT5/32
0.015
1SBN050020R1000
12...32
–
1SBN050020R1002
0.015
50...90
RT5/90
●
RT5 25...65 – – ● RT5/65 1SBN050020R1001 2 2 0.015
77...150 – ● RT5/150 1SBN050020R1003 2 0.015
150...264 – ● RT5/264 1SBN050020R1004 2 0.015
72.5 2.85" 45 1.77" 45 1.77"
Easy connection to the coil terminals
(parallel mounting)
Clip-on for both fixing and connection.
68 2.68" 68 2.68" No additional space
Clipped onto the right side part of the
contactor base without changing con-
tactor overall dimensions and keeping a
1SBC101494S0201
free access to coil terminals.
Main dimensions mm, inches