6-20
Preventing Overvoltage During Deceleration
(Stall Prevention During Deceleration Function)
This function automatically lengthens the deceleration time with respect to the DC-bus voltage to avoid over-
voltage tripping.
Related Constants
Setting the Stall Prevention Selection During Deceleration (L3-04)
There are four different settings selectable for L3-04.
L3-04=0: This setting disables the stall prevention function during deceleration. The motor will be deceler-
ated using the time set in C1-02 (C1-04). If the load inertia is very high and an OV fault occurs dur-
ing deceleration a Braking option has to be used or the time has to be lengthened.
L3-04=1: This setting enables the stall prevention during deceleration. The inverter tries to decelerate within
the set deceleration time. It also observes the DC bus voltage. If the DC bus voltage reaches the
stall prevention level the deceleration is stopped and the output frequency is held. When the DC
bus voltage falls below the stall prevention level the deceleration will be continued.
L3-04=2: This setting enables the stall prevention during deceleration. The deceleration time set as C1-
is taken as reference. The function automatically tries to optimize the deceleration time by observ-
ing the DC bus voltage and shortening the deceleration time. The function does not lengthen the
deceleration time, i.e. if C1- is set too short OV may occure.
Setting Example
An example of stall prevention during deceleration when L3-04 is set to 1 is shown below.
Fig 6.20 Stall Prevention During Deceleration Operation
Con-
stant
Number
Name Description
Setting
Range
Factory
Setting
Change
during
Opera-
tion
Access
Level
L3-04
Stall prevention selection during
deceleration function selection
0: Disabled (Motor decelerates according to setting.
When the deceleration time is too short, there is a risk
of DC bus overvoltage (OV) occurring.)
1: Enabled
2: Optimum adjustment
If using the dynamic brake option (braking resistor units
and braking units), be sure to set constant L3-04 to 0.
0 to 2 1 No A
Deceleration time controlled to
prevent overvoltage
Deceleration time
(set value)
Time
Output frequency
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