for the user to adjust the performance of the controller. The following is a guide to setting the gains for different applications.
Current limit operation
The current limits will normally operate with an integral term only, particularly below the point where field weakening begins. The proportional term is
inherent in the loop. The integral term must be increased enough to counter the effect of the ramp which is still active even in current limit. For example,
if the drive is operating at constant frequency and is overloaded the current limit system will try to reduce the output frequency to reduce the load. At the
same time the ramp will try to increase the frequency back up to the demand level. If the integral gain is increased too far the first signs of instability will
occur when operating around the point where field weakening begins. These oscillations can be reduced by increasing the proportional gain. A system
has been included to prevent regulation because of the opposite actions of the ramps and the current limit. This can reduce the actual level that the
current limit becomes active by up to 12.5%. This still allows the current to increase up to the current limit set by the user.
However the current limit flag (
Current limit active
(10.009)) could become active up to 12.5% below the current limit depending on the ramp rate being
used.
Torque control
Again the controller will normally operate with an integral term only, particularly below the point where field weakening begins. The first signs of
instability will appear around rated frequency, and can be reduced by increasing the proportional gain. The controller can be less stable in torque control
mode compared to when it is used for current limiting. This is because load helps to stabilise the controller, and under torque control the drive may
operate with light load. Under current limit the drive is often under heavy load unless the current limits are set at a low level.
Supply loss and standard ramp
The d.c. link voltage controller becomes active if supply loss detection is enabled and the drive supply is lost or standard ramp is being used
(
Ramp Mode Select
(02.004) > 0) and the motor is regenerating. The d.c. link controller attempts to hold the d.c. link voltage at a fixed level by
controlling the flow of current from the drive inverter into its d.c. link capacitors. The system is forced into current control mode and the output of the d.c.
voltage controller is fed into the current controller as shown below.
Although it is not usually necessary, the d.c. link voltage controller gain can be adjusted with the
Voltage Controller Gain
(05.031). However, it may be
necessary to adjust the current controller gains to obtain the required performance. If the gains are not suitable it is best to set up the drive in torque
control first. Set the gains to a value that does not cause instability around the point at which field weakening occurs. Then revert back to open loop
frequency control in standard ramp mode. To test the controller the supply should be removed whilst the motor is running. It is likely that the gains can
be increased further if required because the d.c. link voltage controller has a stabilising effect, provided that the drive is not required to operate in torque
control mode.
Parameter
04.001
Current Magnitude
Short description
Shows the instantaneous drive output current
Mode
Open
‑
loop
Minimum
−VM_DRIVE_CURRENT
Maximum
VM_DRIVE_CURRENT
Default
Units
A
Type
32 Bit Volatile
Update Rate
16ms
Display Format
Standard
Decimal Places
2
Coding
RO, FI, VM, ND, NC, PT
Current Magnitude
(04.001) is the instantaneous drive output current scaled so that it represents the r.m.s. phase current in Amps under steady state
conditions.
Parameter
04.002
Torque Producing Current
Short description
Shows the instantaneous level of torque producing current
Mode
Open
‑
loop
Minimum
−VM_DRIVE_CURRENT
Maximum
VM_DRIVE_CURRENT
Default
Units
A
Type
32 Bit Volatile
Update Rate
1ms
Display Format
Standard
Decimal Places
2
Coding
RO, FI, VM, ND, NC, PT
Torque Producing Current
(04.002) is the instantaneous level of torque producing current scaled so that it represents the r.m.s. level of torque
producing current under steady state conditions.
Torque Producing Current
(04.002) is proportional to the torque produced by the motor provided field
weakening is not active. For field weakening operation the
Torque Producing Current
(04.002) is boosted for a given level of torque to compensate for
the reduction in the motor flux. The sign of
Torque Producing Current
(04.002) is defined in the table below.
The Rated Torque Producing Current for the motor is given by:
54
Unidrive M200 Parameter Reference Guide
Issue: 01.05.00.10
Summary of Contents for unidrive m200
Page 1: ...Parameter Reference Guide Unidrive M200 Open loop Mode Issue 01 05 00 10 ...
Page 30: ...30 Unidrive M200 Parameter Reference Guide Issue 01 05 00 10 ...
Page 83: ...Enable logic Unidrive M200 Parameter Reference Guide Issue 01 05 00 10 83 ...
Page 125: ...Unidrive M200 Parameter Reference Guide Issue 01 05 00 10 125 ...
Page 145: ...Unidrive M200 Parameter Reference Guide Issue 01 05 00 10 145 ...
Page 204: ...204 Unidrive M200 Parameter Reference Guide Issue 01 05 00 10 ...