- General Electric Computer Accessories User Manual

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• Chapter 3 Paramters/Functions Innovation Series Medium Voltage GP Type - G Drives GEH-6385
Function description
The Speed Reference Ramp function is part of the Speed Reference Generation
function. It operates on the speed reference after the Critical Speed Avoidance
function and before its use in the Speed/Torque Overview function.
The Speed Reference Ramp function limits the rate of change of the speed reference.
Its input (Speed ref, pre ramp) may experience a step change of large magnitude. Its
output (Speed ref, ramped) has the rate limit imposed on it. The user can disable the
Speed Reference Ramp function by setting Ramp bypass to True.
The input to the Speed Reference Ramp is enabled and equal to Speed ref, pre ramp
when Ramp ref enabled is True. When Ramp ref enabled is False, the input to the
ramp is set to zero and the ramp output is allowed to decelerate to zero. More
information on Ramp ref enabled is available in the Sequencer Status function help.
If the drive is configured for flying restart (when Flying restart is set to Enable fly
restart), then the ramp output (Speed ref, ramped) is set to the speed feedback (Speed
reg fbk) when the reference input to the Speed/Torque Regulator is disabled. The
input to the Speed/Torque Regulator is disabled when Speed ref enabled is False.
This feature allows the speed reference to ramp from the speed feedback to the
specified ramp input when the Speed/Torque Regulator reference input is enabled.
More information on Flying restart is available in the Sequencer Permissives
function help. More information on Speed ref enabled is available in the Sequencer
Status function help.
Two ramp modes are available for the Speed Reference Ramp function: the speed
independent ramp rate mode and the programmed ramp rate mode. The modes differ
in the way the ramp rates are implemented. The modes are selected by Ramp rate
mode. The speed independent ramp rate mode is active when Ramp rate mode is set
to Indep accel/decel. The programmed ramp rate mode is active when Ramp rate
mode is set to Prog accel/decel.
When the speed independent ramp rate mode is active, one acceleration rate and one
deceleration rate are implemented for all speeds. The rate of change of the speed
reference is limited to the acceleration rate when the magnitude of the speed
reference is increasing. The rate of change of the speed reference is limited to the
deceleration rate when the magnitude of the speed reference is decreasing. The
acceleration and deceleration ramp rates belong to one of two ramp rate sets. Ramp
rate set 1 is defined by Acceleration rate 1 and Deceleration rate 1 and is active
when Ramp rate 2 select selects a False value. Ramp rate set 2 is defined by
Acceleration rate 2 and Deceleration rate 2 and is active when Ramp rate 2 select
selects a True value.
When the programmed ramp rate mode is active, the acceleration and deceleration
rates depend on the magnitude of the speed reference. The following table lists the
ramp rates and the regions where they are active.
Ramp rate Active region
Acceleration rate 1 Abs(Speed ref, pre ramp) <= Accel break point 1
Acceleration rate 2
Accel break point 1 < Abs(Speed ref, pre ramp) <=
Accel break point 2
Acceleration rate 3 Accel break point 2 < Abs(Speed ref, pre ramp)
Deceleration rate 1 Abs(Speed ref, pre ramp) <= Decel break point 1
Deceleration rate 2 Decel break point 1 < Abs(Speed ref, pre ramp) <=
Decel break point 2
Deceleration rate 3 Decel break point 2 < Abs(Speed ref, pre ramp)