Danfoss VLT Micro Drive FC 51 Programming Manual page 24

Parameter Descriptions ®
VLT Micro Drive FC 51 Programming Guide
4.4.4 3-4* Ramp 1
A linear ramp is characterized by ramping up at a constant
speed until the desired motor speed has been reached.
Some overshoot may be experienced when reaching
speed, which may cause speed jerks for a short while
before stabilizing.
An S-ramp accelerates more smoothly thus compensating
for jerks when the speed is reached.
See Illustration 4.6 for a comparison of the two ramp types.
Speed
Ramp (X) S-Ramp
Ramp (X) S-Ramp
Ratio at Dec.End
Ratio at Accel.End
Ramp (X)
Ramp (X) Linear
S-Ramp
S-Ramp
Ratio at
Jerk compensated
Ratio at
Dec.End
Accel.End
Ramp (X)
Ramp (X)
Up Time
Down Time
Illustration 4.6
Ramp Times
Ramp up: Acceleration time from 0 to nominal motor
frequency (1-23 Motor Frequency).
Deceleration time from nominal motor frequency (1-23
Motor Frequency) to 0.
Limitation
Too short ramp up time can result in Torque limit warning
(W12) and/or DC over voltage warning (W7). Ramping is
stopped when the frequency converter has reached Torque
limit motor mode (4-16 Torque Limit in Motor Mode).
Too short ramp down time can result in Torque limit
warning (W12) and/or DC over voltage warning (W7).
Ramping is stopped when the frequency converter reaches
the Torque limit generator mode (4-17 Torque Limit in
Generator Mode) and/or the internal DC over voltage limit.
3-40 Ramp1 Type
Option: Function:
[0] * Linear Constant acceleration/deceleration.
[2] S-ramp Smooth jerk compensated acceleration/
deceleration.
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3-41 Ramp1 Ramp-up Time
Range: Function:
Size [0.05-3600.00 s] Enter ramp-up time from 0 Hz to
related rated motor frequency (f ) set
*
M,N
in 1-23 Motor Frequency.
Choose a ramp-up time ensuring
that torque limit is not exceeded,
see 4-16 Torque Limit in Motor
Mode.
3-42 Ramp1 Ramp-down Time
Range: Function:
Size [0.05-3600.00 Enter ramp down time from rated
related * s] motor frequency (f ) in 1-23
M,N
Motor Frequency to 0 Hz.
Choose a ramp down time that
does not cause over-voltage in
inverter due to regenerative
operation of motor. Furthermore,
regenerative torque must not
exceed limit set in 4-17 Torque
Limit in Generator Mode.
4.4.5 3-5* Ramp2
See parameter group 3-4* Ramp 1 for a description of
ramp types.
NOTE
Ramp2 - alternative ramp times:
Changing from Ramp1 to Ramp2 is done via the digital
input. See 5-1* Digital Inputs, option [34].
3-50 Ramp2 Type
Option: Function:
[0] Linear Constant acceleration/deceleration.
*
[2] S-ramp Smooth jerk compensated acceleration/
deceleration.
3-51 Ramp2 Ramp-up Time
Range: Function:
Size [0.05-3600.00 s] Enter ramp-up time from 0 Hz to
related rated motor frequency (f ) set
*
M,N
in 1-23 Motor Frequency.
Choose a ramp-up time ensuring
that torque limit is not exceeded,
see 4-16 Torque Limit in Motor
Mode.
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