Speed Control, Mode, Regulation & Vector Speed Feedback - Allen-Bradley PowerFlex 70 Reference Manual

2-166 Speed Control, Mode, Regulation & Vector Speed Feedback
Speed Control, Mode,
Regulation & Vector
Speed Feedback
The purpose of speed regulation is to allow the drive to adjust certain
operating conditions, such as output frequency, to compensate for actual
motor speed losses in an attempt to maintain motor shaft speed within the
specified regulation percentage.
The [Speed Mode] parameter selects the speed regulation method for the
drive, and can be set to one of 3 choices on the PowerFlex 70/700. The
PowerFlex 700 Vector option has 5 choices. In addition, [Feedback Select]
in the Vector option, chooses the feedback used for the speed regulator.
• Open Loop - No speed control is offered
• Slip Comp - Slip Compensation is active – approximately 5% regulation
• Process PI - The PI Loop sets the actual speed based on process variables
080 [Speed Mode]
Standard
Sets the method of speed regulation.
[Feedback Select]
Vector
Selects the source for motor speed
feedback. Note that all selections are
available when using Process PI.
"Open Loop" (0) - no encoder is present,
and slip compensation is not needed.
"Slip Comp" (1) - tight speed control is
needed, and encoder is not present.
"Encoder" (3) - an encoder is present.
"Simulator" (5) - Simulates a motor for
testing drive operation & interface check.
Open Loop
As the load on an induction motor increases, the rotor speed or shaft speed
of the motor decreases, creating additional slip (and therefore torque) to
drive the larger load. This decrease in motor speed may have adverse effects
on the process. If the [Speed Mode] parameter is set to "Open Loop," no
speed control will be exercised. Motor speed will be dependent on load
changes and the drive will make no attempt to correct for increasing or
decreasing output frequency due to load.
Slip Compensation
As the load on an induction motor increases, the rotor speed or shaft speed
of the motor decreases, creating additional slip (and therefore torque) to
drive the larger load. This decrease in motor speed may have adverse effects
on the process. If speed control is required to maintain proper process
control, the slip compensation feature of the PowerFlex drives can be
enabled by the user to more accurately regulate the speed of the motor
without additional speed transducers.
Default: 0 "Open Loop"
Options: 0 "Open Loop"
1 "Slip Comp"
2 "Process PI"
Default: 0 "Open Loop"
Options: 0 "Open Loop"
1 "Slip Comp"
2 "Reserved"
3 "Encoder"
4 "Reserved"
5 "Simulator"