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Connecting to PLCs and Other Devices
Operations
and Monitoring
4–4
Connecting to PLCs and Other Devices
Hitachi inverters (drives) are useful in many types of applications. During installation,
the inverter keypad (or other programming device) will facilitate the initial configura-
tion. After installation, the inverter will generally receive its control commands through
the control logic connector or serial interface from another controlling device. In a
simple application such as single-conveyor speed control, a Run/Stop switch and poten-
tiometer will give the operator all the required control. In a sophisticated application,
you may have a programmable logic controller (PLC) as the system controller, with
several connections to the inverter.
The variety of applications is practically endless, and is beyond the scope of this manual.
It will be important for you to know the electrical characteristics of the devices you want
to connect to the inverter. Then, this section and the following sections on I/O terminal
functions can help you quickly and safely connect those devices to the inverter.
CAUTION: It is possible to damage the inverter or other devices in your application if
the maximum current or voltage characteristics of a connection point are exceeded.
The connections between the inverter and
other devices rely on the electrical input/
output characteristics at both ends of each
connection, shown in the diagram to the
right. The inverter’s inputs require a
sourcing output from an external device
(such as a PLC). This chapter shows the
inverter’s internal electrical component(s)
at each I/O terminal. In some cases, you
will need to insert a power source in the
interface wiring.
In order to avoid equipment damage and
get your application running smoothly, we
recommend drawing a schematic of each
connection between the inverter and the
other device. Include the internal compo-
nents of each device in the schematic, so
that it makes a complete circuit loop.
After making the schematic, then:
1. Verify that the current and voltage for
each connection is within the operating
limits of each device.
2. Make sure that the logic sense (active high or active low) of any ON/OFF connection
is correct.
3. Check the zero and span (curve end points) for analog connections, and be sure the
scale factor from input to output is correct.
4. Understand what will happen at the system level if any particular device suddenly
loses power, or powers up after other devices.
Other device
Input
circuit
Output
circuit
L100 Inverter
Input
circuit
Output
circuit
signal
return
signal
return
P24
1
2
3
6
4
5
L
Input
circuits
+
–
24V
PLC
Inverter
COM
Technologies Inc.
Toll Free: voice: 1-877-539-2542 fax: 1-800-539-2542 www.mgitech.com