Section 5: Configuration of the frequency converter
5.9. Motopotentiometer
The motopotentiometer is an "increase-decrease" system designed to control
the electric motor speed by means of two monostable switches connected to
the digital inputs. To use the motopotentiometer function:
•
connect two monostable switches to any two digital inputs, e.g. DI5 and
DI6.
The use of other digital inputs is possible after making sure that they do
not perform other functions:
◦
DI4 input is by default used as external fault reset (par. 3.70)
◦
DI1, DI2, DI3 inputs can be used as Start / Stop signal sources and
direction changes (par. 2.08) when the frequency converter is con-
trolled from the control terminal block, i.e. for control from the place
A: par. 2.04 and 2.06 = "0"-DI, and for control from the place B: par.
2.05 and 2.07 = "0" -DI;
•
set the motopotentiometer as a speed referencing-unit; depending on the
control place selected in parameter 2.01 (by default, it is control A: par.
2.01 = "0" – Disable), set
par. 2.02
(for control A) or
2.03
(for control B)
to the value
"5" -MotPot;
•
set as the signal source "increase" (
par. 2.20
) and "decrease" (
par. 2.21
)
digital inputs DI, to which monostable switches have been connected.
The possible settings of par. 2.20 and 2.21:
"0" - off, "1" - DI1, "2" - DI2.."6" - DI6.
Four modes of operation are possible (
0, 1, 2, 3
):
0:
stopping the frequency converter operation (STOP) causes
resetting of the motopotentiometer setting;
1:
after stopping the frequency converter operation (STOP), the value
of the motopotentiometer setting will be stored and it is not possible to
change the motopotentiometer setting during standstill.
2:
the value of the current referencing-unit setting is monitored by the
motopotentiometer, which enables a gentle switching from the current
referencing-unit to the referencing-unit from the motopotentiometer.
3:
after stopping the frequency converter operation, the
motopotentiometer setting value will be saved, it is possible to change
the motopotentiometer setting during standstill.
An example of how to connect the "increase" and "decrease" buttons is
shown in Fig. 5.5a. The operation of the system is illustrated in Fig. 5.5b.
38
TWERD Power Electronics
