Rockwell Automation 1503 IntelliVAC Contactor Control Module - Series C and later - Manual (Page 25)

3-12 Installation and Wiring
1503-UM052D-EN-P – June 2013
Control with Solid-State Devices
If control devices that employ electronic or suppressed output circuits are
used in the rung(s) that control the inputs to the IntelliVAC, alternate
arrangements may be required. Devices employing transistor or triac
output circuits have finite impedance and allow a leakage current to flow
in the blocking or off state. Some PLC and I/O modules with relay
outputs also have R-C snubber circuits across the contacts to suppress
noise generated during contact opening. The impedance of these circuits
also allows leakage current to flow when the contacts are open. The high
impedance input circuits of the IntelliVAC may be triggered by this
leakage current or residual terminal voltage, causing unintended
operation of the contactor, or maintenance of the closed state when the
control signal is removed.
This situation can be prevented by consideration of the control devices
when designing the control system. If PLC or similar control devices are
to be interfaced to the IntelliVAC, consider using relay outputs with no
suppression devices across the contacts (the IntelliVAC inputs are a high
impedance, resistive load). If this cannot be done, consider the leakage
current of the device to see if it is compatible with IntelliVAC inputs (see
Table 1.A). If not compatible, consider using an interposing relay
connected as shows in Figure 3.6.
- +
3
2
12
11
AUX
MOV
M
TCO
5
6
-
+
1
EC
CCO
4
9 10
M
CLOSE
N
G
OVERLOAD
*
CONTROL
POWER
FUSE
CONTROL POWER
M
M -IV
M -IV
L
CR
CR
SOLID STATE
OUTPUT
INPUT POWER
* Refer to Table 3.A for recommended fuse sizing.
Figure 3.6 – Control with Solid-State Devices