HARDWARE MANUAL Document reference MAMPS-HW/E
VM600 machinery protection system (MPS) Edition 18 - March 2022
9-38
Channel inhibit function
CONFIGURATION OF MPC4 / IOC4T CARDS
reference/return is known as RET and is available on Connector J3, Terminal 8
(see 9.1 Definition of screw terminals on the IOC4T card).
NOTE: The common reference/return (RET) signal has a voltage limit of ±2V and a
current limit of 100 mA.
Accordingly, it is recommended to use galvanic separation between the RET on
the IOC4T card and any circuitry connected to the discrete signal interface (DSI)
inputs if the potential difference between RET and the external circuitry could be
greater than 2 V.
For further information on the Danger Bypass function, see 4.6.5 Danger Bypass function
and for further information on the Direct Trip Multiply function, see 4.6.4 Direct Trip Multiply.
9.8 Channel inhibit function
The channel inhibit function can only be activated using software, that is, there is no
equivalent DSI input.
The channel inhibit function is activated when one of the VM600 MPSx software packages
(MPS1 or MPS2) is used to send channel inhibit commands to individual MPC4 channels
(Communications > To MPC > Channel Inhibits).
Alternatively, Modbus can be used to control the channel inhibit function for a networked
VM600 machinery protection system (containing a CPUM card).
For further information on the channel inhibit function, see 4.6.6 Channel inhibit function.
9.9 Slot number coding for IOC4T cards
IOC4T cards use an electronic keying mechanism to help prevent them from being installed
in the wrong slot of a VM600 rack. Each IOC4T card has a bank of micro-switches that are
used to assign a slot number to the card, stored in the slot number (address) assignation
register.
The IOC4T card compares its slot number with the rack’s slot number (see Figure 2-2). The
result of the comparison is displayed on the SLOT ERROR LED on the cards panel:
• If the codes are identical, the LED is green.
• If the codes are not identical, the LED is red.
9.9.1 VM600 system rack (ABE04x)
When an IOC4T card is installed in a VM600 system rack (ABE04x), the micro-switches on
the card must be configured to match the rack slot (slot number) being used (see 2.1.1.1 Slot
number coding for cards in the rear of a VM600 system rack).
The example in Figure 9-27 shows the micro-switch settings required for an IOC4T card
installed in slot 11 of a VM600 system rack.
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