Interface - PowerTec 2000C Instruction Manual

damaging the transistor or the power supply of the control.
DO NOT USE THE ZERO SPEED RELAY CONNEC-
TION SHOWN IN FIGURE 22 WITHOUT CONNECT-
ING THE DIODE AS SHOWN.
The relay turns on when the motor is turning more
than 10 RPM and stays on until the motor is no longer
turning faster than 10 RPM. There is ahysteresis built in.
The Zero Speed output is useful for determining if
the motor is actually running. The pulses which control the
Zero Speed output come directly from the motor. It is not
necessary to use an external Zero Speed circuit to shut off
the Model 2000C. There is a built in RAMP STOP func-
tion. However, it is sometimes necessary to detect Zero
Speed in a system.
On light loads at very low speed, the motor speed
may change enough to cause the Zero Speed relay to
"chatter", especially with high gain or an incorrect STA-
BILITY adjustment. This is caused by the rapid accumu-
lation and discharge of pulses in the counting circuits
which determine Zero Speed. Chatter does not affect the
internal RAMP STOP function. The chatter is most likely
to occur at low speeds and when things are happening
quickly. As the load increases on the motor, the amount of
chatter will be less.
The chatter may be overcome by using the Zero
Speed output to indirectly control an external relay which
Figure 23: A circuit to eliminate chatter on the zero
speed relay.
will perform the Zero Speed function, shutting off the first
time the Zero Speed relay opens up and requiring some
other signal to turn on again. A typical circuit is shown in
Figure 23.
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Page
4.6 PLC INTERFACE
The interface of the Models 2000C and 3000C with
a process controller is dependent upon the ability of the PC
to handle the required signals. Most of the signals are
+24VDC or +24VDC and -24VDC for control, or +10VDC
for speed. Computer generated frequency signals may also
be used for speed (see Section 4.5.2 and Figures 16 and 17).
Figure 24 illustrates the method for using an open
collector output to sink the input of a +24VDC PC input
Figure 24: SINKING connection to a PLC.
module. There are two types of input modules. A sourcing
connection supplies voltage from the input source, but in
the sinking connection, voltage supplied by the module
and connected (sunk) to common by the connected input
device. Figure 25 shows a sourcing connection.
Figure 25: SOURCING connection to a PLC.
With PLC's, it is recommended that all operation of
the control circuits of the Models 2000C and 3000C be
done with relays. These circuits see 24VDC to ground, but
they operate at 48VDC . RUN, JOG, STOP and EMER-
GENCY STOP operate on +24VDC supplies, but the
circuitry is connected between positive and negative sup-
plies, and it is difficult to make connections which do not
involve both power supplies.
Model 2000C / 3000C Manual