User Manual

Chapter 7 Explanation of Functions
7 - 59
<2> DC voltage constant control during nonstop operation at momentary power failure (b050 = 02: no
restoration, b050 = 03: restoration to be done)
- If momentary power failure occurs or the main circuit DC voltage drops during inverter operation, the
inverter decelerates the motor while maintaining the main circuit DC voltage at the level specified as the
target nonstop operation voltage at momentary power failure (0V-LAD stop level) (b052).
- This function starts operating when all the following conditions are met:
-- "02" or "03" has been specified for b050.
-- The inverter is running. (This function does not operate if the inverter has been tripped, is in
undervoltage status or stopped.)
-- The control power fails momentarily or the main circuit DC voltage drops to the DC bus voltage
trigger level during power loss (b051) or less.
- If momentary power failure only lasts a short time, the inverter can continue operation without stopping its
output. Conversely, if momentary power failure causes undervoltage, the inverter stops its output
immediately and ends the operation of this function. When power is subsequently restored, the inverter
operates according to the selection of restart mode (b001).
- When "03" is specified for b050, the inverter can be restored to normal operation if the input power is
recovered from momentary power failure before the inverter stops its output. The inverter, however, may
decelerate and stop the motor if a specific setting has been made for b051. The table below lists the
differences in operation according to the setting of b051.
b050 b051 Operation
02 (No
restoration)
b052 > Main circuit DC voltage at input power recovery
Decelerating and stopping the motor (DC voltage
constant control) (Example 1)
b052 < Main circuit DC voltage at input power recovery Decelerating and stopping the motor (Example 2)
03 (Restoration
to be done)
b052 > Main circuit DC voltage at input power recovery
Decelerating and stopping the motor (DC voltage
constant control) (Example 1)
b052 < Main circuit DC voltage at input power recovery Decelerating and stopping the motor (Example 2)
- When this function operates and the inverter decelerates and stops the motor, the motor is forcibly
stopped even if the FW signal is on. To restart the motor, turn on the FW signal again after confirming the
recovery of inverter input power.
Note 4: Each of the values of b051 and b052 must be the undervoltage 175V(200V class),350V(400V
class)level or more. This function does not operate when undervoltage occurs. The value of b051 must
be less than that of b052.
Note 5: When "02" or "03" is specified for b050, PI control is performed so that the internal DC voltage is
maintained at a constant level. PI-gain (P-Gain,I-Gain) can adjust by b133(P) and b134(I).
(Example 1) (Example 2)
b050=02
(decelerate to stop)
Period of DC voltage
constant control
Voltage across main circuit terminals P and N
Vpn(V)
Time
Time
Output frequency
(Hz)
b050=03(running)
b052
b051
Voltage across main circuit terminals P and N
Vpn(V)
Time

Time
Output frequency
(
Hz
)
P
er
i
o
d
o
f
DC
vo
lt
age
constant control
b050=02,03
(decelerate to stop)
DC
vo
lt
age across ma
i
n c
i
rcu
it
Recovery of input power
b052
b051
DC
vo
lt
age across ma
i
n c
i
rcu
it
Recovery of input power
Recover
y
of in
p
ut
p
owe
r
Recover
y
of in
p
ut
p
owe
r