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Chapter 4
<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.
- This function operates when the conditions above are met even if the J51 connector cables have been disconnected
from terminals R0 and T0, and cables are connected from main circuit terminal P to terminal R0, and from main
circuit terminal N to terminal T0.
- 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
b052 > Main circuit DC voltage at input power recovery
02 (No restoration)
b052 < Main circuit DC voltage at input power recovery
03 (Restoration to
b052 > Main circuit DC voltage at input power recovery
be done)
b052 < Main circuit DC voltage at input power recovery
- 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 210V(200V class),410V(400V class)level or
more. This function does not operate when undervoltage occurs. The value of b051 must be less than that of b052.
When b051 is much higher proportional gain (b055) results in overcurrent by rapid acceleration after this function
operates.
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.
- Setting a higher proportional gain (b055) results in a faster response. However, an excessively high proportional gain
causes the control to diverge and results in the inverter easily tripping.
- Setting a shorter integral time (b056) results in a faster response. However, an excessively short integral time results
in the inverter easily tripping.
- Setting a lower proportional gain (b055) results in undervoltage trip due to a voltage drop immediately after starting
this function.
(Example 1)
Voltage across main circuit terminals P and N
Vpn(V)
DC voltage across main circuit
Recovery of input power
Period of DC voltage
Output frequency
(Hz)
b050=02,03
(decelerate to stop)
b051
constant control
Recovery of input power
Decelerating and stopping the motor (DC voltage
constant control) (Example 1)
Decelerating and stopping the motor (Example 2)
Decelerating and stopping the motor (DC voltage
constant control) (Example 1)
Decelerating and stopping the motor (Example 2)
(Example 2)
Voltage across main circuit terminals P and N
Vpn(V)
b052
b051
DC voltage across main circuit
Recovery of input power
Time
Output frequency
(Hz)
Time
4-84
Explanation of Functions
Operation
Period of DC voltage
constant control
b050=03(running)
b050=02
(decelerate to stop)
Recovery of input power
b052
b051
Time
Time
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