Torque Performance Modes - Allen-Bradley PowerFlex 70 Reference Manual

2-178

Torque Performance Modes

Torque Performance
Modes
[Torque Perf Mode] selects the output mode of the drive. The choices are:
• Custom Volts/Hertz
Used in multi-motor or synchronous motor applications.
• Fan/Pump Volts/Hertz
Used for centrifugal fan/pump (variable torque) installations for
additional energy savings.
• Sensorless Vector
Used for most general constant torque applications. Provides excellent
starting, acceleration and running torque.
• Sensorless Vector w/Economizer
Used in constant torque applications that have significant "idle" time
(time spent at greatly reduced load) to offer additional energy
conservation.
The following table shows the performance differences between V/Hz and
Sensorless Vector.
Torque Mode
Speed Regulation/accuracy (w/
slip compensation)
Operating Speed Range (w/slip
compensation)
Dynamic Speed Accuracy
(speed response to a 95% step
load change)
Velocity Bandwidth (w/slip
compensation and no encoder)
Minimum setting of velocity
bandwidth/slip compensation
Volts/Hertz
Volts/Hertz operation creates a fixed relationship between output voltage
and output frequency. The relationship can be defined in two ways.
1. Fan/Pump
When this option is chosen, the relationship is 1/X
for full frequency, full voltage is supplied and for 1/2 rated frequenc y,
1/4 voltage is applied, etc. This pattern closely matches the torque
requirement of a variable torque load (centrifugal fan or pump – load
increases as speed increases) and offers the best energy savings for these
applications.
Maximum Voltage
Base Voltage
(Nameplate)
Run Boost
Fan/Pump and
Custom V/Hz SVC
0.5% 0.5%
40:1 80:1
0.5% base 0.5% base
speed speed
10 rad/s 20 rad/s (50
rad/s desired)
0.1 rad/s 0.1 rad/s
Base Frequency
Maximum
(Nameplate) Frequency
2
. Therefore;