Rockwell Automation Allen-Bradley PowerFlex 755T Flux Vector Tuning User Manual

Rockwell Automation Publication 750-AT006D-EN-P - January 2022 27
Chapter 2
Product Features
Torque Scaler
Torque Scaler (K
J
) is a torque loop gain that accounts for load inertia by multiplying by its inverse. Inertia converts torque to acceleration,
then the torque scaler converts acceleration to torque. Scaling torque does the following:
• Makes the velocity loop response match the velocity loop bandwidth
• Allows the velocity loop response to not be affected by motor gain or load inertia
• Calibrates the control loops so that all gains represent physically measurable bandwidths
• Scales the system under control to unity gain
• Acts as an overall system gain
This section includes:
• Explanation of Calculation
on page 27
• Cases of Calculation on page 27
Explanation of Calculation
Torque Scaler is calculated from the following parameters. It is a function of rated motor torque and total inertia.
10:403 [Motor NP RPM]
10:405 [Mtr NP Pwr Units]
10:406 [Motor NP Power]
10:900 [Motor Inertia]
10:901 [Load Ratio]
Torque Scaler is recalculated any time one of these parameters change.
Equations for torque scaler are given:
• When 10:405 [Mtr NP Pwr Units] = 0 and 10:406 [Motor NP Power] are in units of Hp:
- Motor Rated Torque [N•m] = ([Motor NP Power] / [Motor NP RPM]) x 7120.91
- System Acceleration [rev/sec
2
] = [Motor NP Power] /([Motor NP RPM] x [Motor Inertia] x ([Load Ratio]+1)) x 1133.33
• When 10:405 [Mtr NP Pwr Units] = 1 and 10:406 [Motor NP Power] are in units of kW:
- Motor Rated Torque [N•m] = ([Motor NP Power]/[Motor NP RPM]) x 9549.30
- System Acceleration [rev/sec
2
] = [Motor NP Power]/([Motor NP RPM] x [Motor Inertia] x ([Load Ratio] + 1)) x 1519.82
• Torque Scaler [%/(rev/sec
2
)] = 100 / System Acceleration
• Torque Scaler [sec] = [Motor NP RPM]/ (System Acceleration * 60)
Cases of Calculation
This section covers a few cases of calculating Torque Scaler for different types of loads.
Rigid Load
Rigid loads with constant inertia are typically found in high-performance applications. There is a direct coupling to the motor with few
mechanical components. The mechanical components have no flex or twist and there is no misalignment. Figure 25 on page 28
shows a rigid
mechanical load with a load inertia that does not change over time. K
T
is the motor rated torque constant, which is compensated for by block

Rockwell Automation Allen-Bradley PowerFlex 755T Flux Vector Tuning Specifications

General

Brand	Rockwell Automation
Model	Allen-Bradley PowerFlex 755T Flux Vector Tuning
Category	Industrial Equipment
Language	English