LA1KN11 SQUARE D, LA1KN11 Datasheet - Page 26

• Manufacturer Part Number: LA1KN11
• Description: 92F5946
• Manufacturer: SQUARE D

Specifications of LA1KN11

• Leaded Process Compatible: No
• Peak Reflow Compatible (260 C): No
• Rohs Compliant: No
• For Use With: K-Line Contactors

Long Distance Control Data
26
Residual Current in the Coil Due to Cable Capacitance
When the control contact of a relay is opened the cable capacitance is effectively in series with the coil of the electromagnet. This capacitance can cause
a residual current to be maintained in the coil, with the risk that the relay will remain closed.
This only applies to relays operating on an a.c. supply.
This phenomenon is aggravated by:
- a long line length between the coil control contact and the relay, or between the coil control contact and the power supply,
- a high control circuit voltage,
- a low coil consumption, sealed,
- a low value of relay drop-out voltage.
The maximum control cable length, according to the relay coil supply voltage, is indicated in the graph on page 27.
Remedial action
Various solutions can be adopted to avoid the risk of the contactor remaining closed due to cable capacitance:
- use a d.c. control voltage, or,
- add a rectifier, connected as shown in the scheme below, but retaining an a.c. operating coil: in this way, rectified a.c. current flows in the control circuit
cable.
When calculating the maximum cable length, take the resistance of the conductors into account.
- Connect a resistor in parallel with the contactor coil (1).
Value of the resistance:
Power to be dissipated
(1)
R
PW
=
To avoid increasing the voltage drop due to inrush current, this resistor must be brought into operation after the relay has closed by using a
N/O contact.
---------------------------- -
10
=
3 –
U
------ -
R
2
1
C uF
(C capacitance of the control cable)
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–
2001 Schneider Electric All Rights Reserved
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