Rockwell Automation 20B PowerFlex 700 AC Drives Vector Control (v4.001 and up) - Manual (Page 118)

118 Rockwell Automation Publication 20B-UM002G-EN-P - July 2014
Appendix C Application Notes
When encoderless TorqProve is enabled, the drive cannot hold the load at zero
speed. Parameter 606 [Float Tolerance] will then define the speed at which the
brake is set.
Micro Position
Micro Position refers to rescaling of the commanded frequency by a percentage
entered in [MicroPos Scale %], parameter 611. This allows for slower operation
of a lift which provides an operator with better resolution when positioning a
load. Micro Position is activated only when the drive is running at or near zero
speed. This can be initiated by a digital input configured as Micro Pos or through
a communication device ([TorqProve Setup]) which is the same digital input
which signals the float condition. To allow the Micro Position digital input to
change the speed command while the drive is running, enter a “1” in Parameter
600, Bit 2 “MicroPosSel.” A “0” will require drive to reach zero speed for micro
position speed to become active.
Fast Stop
Fast Stop is intended to stop the load as fast as possible then set the mechanical
brake. The Fast Stop can be initiated from a digital input or through a
communication device through [TorqProve Setup]. The difference from a
normal stop is that the decel time is forced to be 0.1 seconds. When the Torque
Proving function is enabled, the Float time is ignored at the end of the ramp. This
feature can be used without enabling the Torque Proving function.
Limit Switches for Digital
Inputs The PowerFlex 700 includes digital input selections for decel and end limit
switches. These can be used for applications that use limit switches for
decelerating near the end of travel and then stopping at the end position. The end
limit switch can also be used for end limit stops as many hoists require. These
inputs can be used with or without TorqProve enabled.
Decel Limit for Digital Inputs
Decel Limit is enabled by selecting “Decel Limit” as one of the digital inputs in
[Digital In1-6 Select], parameters 361-366. When this input is “low” (opposite
logic), the speed reference command will change from the selected reference to
the value in [Preset Speed 1], parameter 101. The deceleration rate will be based
on the active deceleration time. This limit will be enforced only in the direction
the drive was running when the switch was activated (momentarily or
continuously, see “B” in
Figure 8 ). The opposite direction will still be allowed to
run at the selected reference speed. No speed limitation will occur between the
limit switches (“A” in
Figure 8 ).
Two different switches can be connected in series to one digital input to provide a
decel limit at both ends of the application (that is, lift, conveyor, etc.). With
proper set up, the drive will automatically apply the speed reduction based on the
direction of the load even though only one digital input is being used. See “B” in
Figure 8 .