Page 194 - Motor_protection_and_control_Manual_motor_starters_ contactors

Surge suppressors for contactor coils

Description
(V)
1000
The operation of inductive circuits causes overvoltages, in particular on opening the contactor coil.
T (µs)
0 100 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
1000
observed ranging from interference on the electronic devices to the breakdown of insulators and even the
0 100 destruction of certain 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.
4 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. Ûs max. Ûs max.
k = in DC k = in AC k =
Ûc Uc Uc √2
1SBC101042F0014 For example the following is obtained for the above graph: k = 42 √2 ≈ 60
3500

signed to reduce the k factor defined above and to limit or even completely eliminate the high pre-damping
RV5 To reduce the harmful effects of these overvoltages, ABB has developed a range of surge suppressors de-
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 ap-
plied at its terminals.
1SBC101042F0014 Ordering details

contactor
qty
(1 pce)
contactors
voltage - Uc
RC5-1 For For Rated control circuit Type Order code Pkg Weight
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 2 0.012
50...133
RC5-1/133
0.012
1SBN050100R1001
●
1SBC101042F0014 ASL NSL 110...250 ● ● RC5-1/250 1SBN050100R1002 2 2 2 0.012
–
250...440
–
0.012
1SBN050100R1003
RC5-1/440
●
1SBN050020R1000
0.015
RT5/32
–
12...32
RT5 25...65 – ● RT5/65 1SBN050020R1001 2 0.015
50...90 – ● RT5/90 1SBN050020R1002 2 0.015
77...150 – ● RT5/150 1SBN050020R1003 2 0.015
150...264 – ● RT5/264 1SBN050020R1004 2 0.015
Main dimensions mm, inches
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
contactor overall dimensions and 1SBC101494S0201
keeping a free access to coil terminals.
4/74 | ABB