Rockwell Automation 1746-QV,D17466.18 OPEN-LOOP VELOCITY CONTL - Manual (Page 20)

4–4 Setting Up the Hardware
Publication 1746-6.18 April 1998
Application of the
"15V Power Supply
The module uses the
"15V dc power supply to drive the "10V dc
valve output and to power the LDT. The module detects loss of
"15V dc with its internal LDT diagnostic. The diagnostic
concludes loss of
"15V when it detects loss of LDT magnet.
Partial failure of the
"15V dc power supply may cause limited
machine operation when the LDT continues to operate properly. Some
LDTs will operate with its supply voltage down to 12V. If you monitor
the
"15V dc with SLC diagnostics, you can enable a blocking valve
to lock the actuator in its last position upon detection of:
•
e-stop
•
power loss
•
low voltage condition of the
"15V dc supply
ATTENTION: If you provide a system e-stop circuit and design the
system to manage power to the SLC chassis and
"15V dc supply, in
all cases DO NOT connect the e-stop to ac power for power supplies.
ATTENTION: We recommend using reasonable methods to assure
that unintended motion does not cause machine damage or create a
safety issue with personnel who will operate the machine.
(Chapter 5 covers testing for proper system operation.)
•
Use a proportional valve that does not respond to voltage spikes
created by power supply operation.
•
Shut down the hydraulic system upon loss of ac power and
automatically vent pressurized fluid back to the tank.
•
Provide ladder programming that interlocks the operation of the
power supply with permissives to run the hydraulic pump.
•
Connect a high-speed relay between the module and the valve
amplifier to drop-out the valve signal upon loss of ac power.
Other Design
Considerations