Speed Reference - Allen-Bradley PowerFlex 70 Reference Manual

Speed Reference

2-171
Speed Reference
Operation
The output frequency of the drive is controlled, in part, by the speed
command or speed reference given to it. This reference can come from a
variety of sources including:
• HIM (local or remote)
• Analog Input
• Preset Speed Parameter
• Jog Speed Parameter
• Communications Adapter
• Process PI Loop
• Digital Input MOP
Selection
Binary Logic
Some references can be selected by binary logic, through digital inputs to
the terminal block or bit manipulation of the Logic Command Word in a
communications adapter. These sources are used when the drive is in
"Auto" mode. The default reference is from the source selected in [Speed
Ref A Sel], parameter 90. This parameter can be set to any one of the 22
choices. If the binary logic selection is zero, this will be the active speed
reference.
Auto/Manual
Many applications require a "manual mode" where adjustments can be
made and setup can be done by taking local control of the drive speed.
Typically, these adjustments would be made via a "local" HIM mounted on
the drive. When all setup is complete, control of the drive frequency
command is turned over to automatic control from a remote source such as a
PLC, analog input etc.
The source of the speed reference is switched to one of two "manual"
sources when the drive is put into manual mode:
1. Local HIM
2. Analog Input to terminal block
If the selection is the HIM, then the digital or analog speed control on the
HIM provides the reference.
If the switch to manual mode was made via a digital input, (parameters
361-366 set to "18, Auto/Manual") then the source for the reference is
defined in [TB Man Ref Sel], parameter 96. This can be either of the 2
analog inputs or the digital MOP.
When the drive is returned to automatic mode, the speed reference returns to
the source selected by the binary logic. Also see Auto/Manual on page 2-27.