Yaskawa VS-626 MC5 - Manual (Page 146)

Advanced Operation
7.1.4 Operation Selection when Output Voltage Saturated
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7.1.4 Operation Selection when Output Voltage Saturated
The Inverter cannot output a voltage that is higher than the input voltage. If the output voltage command
to the motor (monitor constant U1--06) exceedes the input voltage in the high--speed region, the output
voltage will become saturated, and the control unstable with open loop vector control.
Select one of the following methods to prevent this unstable condition.
J Limited Output Voltage Operation: C3--06 (for SPEC: F)
User
Change
during Setting Factory
Valid Access Levels User
Constant
Number
Name
during
Opera-
tion
Setting
Range Unit
Factory
Setting Open Loop
Vector
Flux Vector
C3--06
Limited output voltage
operation
0 1 1 0 A A
D Settings
Setting Function
0 Disables limited output voltage operation.
1 Enables limited output voltage operation.
D If the limited output voltage operation is disabled and output voltage becomes saturated, slip com-
pensation is automatically disabled to prevent instability.
The output current does not change when the slip compensation is disabled, however precise speed
control is no longer possible. Enable limited output voltage operation if precise speed control is re-
quired.
D If the limited output voltage operation is enabled, the magnetic flux current of the motor is automatical-
ly controlled, and the output voltage command itself is limited, which maintains precise speed control.
Check the Inverter current margins as the output current will be maximum 10% higher (with a rated
load) than when limited output voltage operation is disabled.
Note 1.C3--06 does not need to be changed if the Unit is used only at medium or low speeds, or
when the power supply voltage is 10% or more higher than the rated voltage of the moror,
or when speed precision in the high--speed region is not required.
2. When the power supply voltage is too low for the rated motor voltage, speed control will
not be precise even if limited output voltage operation is enabled.
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