Efficiency Optimization - Siemens SINAMICS G120C USS/MB Operating Instructions Manual

6.29

Efficiency optimization

Overview
The efficiency optimization reduces the motor losses as far as possible.
Efficiency optimization functions under the following preconditions:
● Operation with an induction motor
● Vector control is set in the inverter.
Active efficiency optimization has the following advantages:
● Lower energy costs
● Lower motor temperature rise
● Lower motor noise levels
Active efficiency optimization has the following disadvantage:
● Longer acceleration times and more significant speed dips during torque surges.
The disadvantage is only relevant when the motor must satisfy high requirements relating to
the dynamic performance. Even when efficiency optimization is active, the inverter closed-loop
motor control prevents the motor from stalling.
Figure 6-66
The three variables that the inverter can directly set, which define efficiency of an induction
motor, are speed, torque and flux.
However, in all applications, speed and torque are specified by the driven machine. As a
consequence, the remaining variable for the efficiency optimization is the flux.
The inverter has two different methods of optimizing the efficiency.
Efficiency optimization, method 2
Generally, energy efficiency optimization method 2 achieves a better efficiency than method 1.
SINAMICS G120C converter
Operating Instructions, 09/2017, FW V4.7 SP9, A5E34263257B AF
Efficiency optimization by changing the motor flux
Advanced commissioning
6.29 Efficiency optimization
311