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274
Special operation and frequency control
4.21.2
Bypass-inverter switchover function (pr. 57, Pr. 58, Pr. 135 to Pr. 139, Pr. 159)
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⋅ When the motor is operated at 60Hz (or 50Hz), more efficient operation can be performed by the commercial power
supply than by the inverter. When the motor cannot be stopped for a long time for the maintenance/inspection of the
inverter, it is recommended to provide the commercial power supply circuit.
⋅ To avoid commercial power supply being applied to the inverter output side when switching between inverter
operation and commercial power supply operation, provide an interlock which the MC of the commercial power
supply side turns ON only when the MC of the inverter output side is OFF. Using the electronic bypass sequence
function that outputs the timing signal for operation of the magnetic contactor, a complicated commercial power
supply switchover interlock can be provided by the inverter.
The complicated sequence circuit for bypass operation is built in the inverter. Hence, simply inputting the start,
stop or automatic switchover selection signal facilitates the interlock operation of the switchover magnetic
contactor.
Parameter
Number
Name
Initial
Value
Setting
Range
Description
57 Restart coasting time 9999
0
⋅ 1.5K or lower.....................................................0.5s,
⋅ 2.2K to 7.5K
.................................................1s,
⋅ 11K to 55K
...................................................3.0s,
⋅ 75K or higher ....................................................5.0s,
The above times are coasting time.
55K or
lower
0.1
to 5s
Set the waiting time for inverter-triggered restart after an
instantaneous power failure.
75K or
higher
0.1
to
30s
9999 No restart
58 Restart cushion time 1s 0 to 60s Set a voltage starting time at restart.
135
Electronic bypass sequence
selection
0
0 Without electronic bypass sequence
1 With electronic bypass sequence
136
MC switchover interlock
time
1s 0 to 100s Set the operation interlock time of MC2 and MC3.
137 Start waiting time 0.5s 0 to 100s
Set the time slightly longer (0.3 to 0.5s or so) than the time
from when the ON signal enters MC3 until it actually turns
ON.
138 Bypass selection at a fault 0
0 Inverter output is stopped (motor coast) at inverter fault.
1
Operation is automatically switched to bypass operation
at inverter fault (Not switched when an external thermal
relay operation (E.OHT) or CPU fault (E.CPU) occurs).
139
Automatic switchover
frequency from inverter to
bypass operation
9999
0 to 60Hz
Set the frequency to switch inverter operation to bypass
operation.
Inverter operation is performed from a start until Pr. 139
is reached, and when the output frequency is at or
above Pr. 139, inverter operation is automatically
switched to bypass operation.
9999 Without automatic switchover
159
Automatic switchover
frequency range from
bypass to inverter operation
9999
0 to 10Hz
Valid during automatic switchover operation (Pr. 139 ≠
9999)
When the frequency command decreases below (Pr. 139
- Pr. 159) after operation is switched from inverter
operation to bypass operation, the inverter automatically
switches operation to inverter operation and operates at
the frequency of frequency command. When the inverter
start command (STF/STR) is turned OFF, operation is
switched to inverter operation also.
9999
Valid during automatic switchover operation (Pr. 139 ≠
9999)
When the inverter start command (STF/STR) is turned
OFF after operation is switched from inverter operation
to bypass operation, operation is switched to inverter
operation and the motor decelerates to stop.
The above parameters can be set when Pr. 160 User group read selection = "0". (Refer to page 201.)
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