SJ700-2 Instruction Manual NT204DX - Hitachi America, Ltd.

Chapter 4 Explanation of Functions
(Example 3) Restarting with active matching frequency
Output current
Inverter output
frequency
Motor speed
FW
FRS
b003
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).
NFB
b028
Deceleration according to
the setting of "b029"
Frequency selected as the
setting of "b030"
ELBC
FWY
RVY
CSY
MC2
MC1
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
Sample connection diagram and timing charts for
commercial power supply switching
R
S
T
R0
T0
H
O
L
FW
RV
CS
CM1
U
V
W
AL1
AL2
AL0
MC3
THRY
Motor
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