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Chapter 4
(Example 3) Restarting with active matching frequency
FW
FRS
Output current
Inverter output
frequency
Motor speed
4.2.48 Commercial power source switching (CS) function
The commercial power source switching function allows you to switch the
power supply (between the inverter and commercial power supply) to your
system of which the load causes a considerable moment of inertia. You can
use the inverter to accelerate and decelerate the motor in the system and
the commercial power supply to drive the motor for constant-speed
operation.
To use this function, assign function "14" (CS) to one of the terminal [1] to [8] functions (C001 to C008).
When the CS terminal is turned off with an operation command being input, the inverter waits for the retry wait time
before motor restart (b003), adjusts the output frequency to the speed of the free-running motor, and then
accelerates the motor with the adjusted frequency. (The start mode is the starting with matching frequency.) However,
the inverter may start the motor with 0 Hz if:
1) the motor speed is no more than half the base frequency or
2) the voltage induced on the motor is attenuated quickly.
3) If the motor speed falls to the restart frequency threshold (b007), the inverter will start the motor with 0 Hz. (See
Section 4.2.27.)
Remark) Mechanically interlock the MC3 and MC2 contacts with each other. Otherwise you may damage the drive.
If the earth-leakage breaker (ELB) trips because of a ground fault, the commercial power will be disabled. Therefore,
connect a backup power supply from the commercial power line circuit (ELBC) to your system if needed.
Use weak-current type relays for FWY, RVY,
and CSY. The figures below show the
sequence and timing of operations for
reference.
If the inverter trips because of overcurrent
when it starts the motor with matching
frequency, increase the retry wait time
before motor restart (b003).
For circuit connections and switching
operations, see the sample connection
diagram and timing charts for commercial
power supply switching as shown on the
right.
The inverter can be set up so that it will
automatically retry operation at power-on.
In such cases, the CS terminal (signal) shown
in the figures below is not required. For
details, see the explanation of the reset (RS)
function (4.2.29).
b028
Deceleration according to the
setting of "b029"
Frequency selected as the setting
of "b030"
b003
Sample connection diagram and timing charts for commercial
ELBC
NF
B
4-53
Explanation of Functions
After the retry wait time (b003), the
inverter restarts the motor with the
frequency set as "b030". The inverter
subsequently decelerates the motor
according to the setting of "b029" while
maintaining the output current at the
level specified for "b029".
When the output voltage matches the
frequency, the inverter re-accelerates
the motor up to the frequency that was
set when the inverter shut off the
output to the motor before the restart.
If the inverter trips because of
overcurrent when it restarts the motor
with input frequency, reduce the setting
of "b028".
Related code
b003: Retry wait time before motor restart
b007: Restart frequency threshold
C001 to C008: Terminal [1] to [8] functions
power supply switching
MC
2
MC
R
U
1
S
V
T
W
R0
T0
H
O
L
AL1
AL2
F
AL0
W RV
FW
Y RVY
CS
CSY
CM
1
THR
MC
Y
3
Motor
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