ZES ZIMMER LMG450, User Manual

Page: 68 / 306

Instrument controls LMG450
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4.4.4.2.15 Example 6: Calculation of the efficiency of a motor with torque and
frequency input
For the measurement of the efficiency of a motor you can use the analogue and the frequency
inputs. To input the torque of the motor use the analogue input (e.g. 1) and for the frequency
use the digital frequency input (e.g. card1 Pin 12). For calculation of the efficiency you can use
the following formula:
M=Ain:1;
n=DigFrq:1;
Pmech=M*n;
eta=Pmech/P:13*100;
Important Note: The motor frequency connected to the frequency input (No.1) has to be
counted and scaled in Hz. Then you get a result in percent.
4.4.4.3 Printing scripts
You can printout the scripts you have set-up (see 11, ‘Logging of values to drives, printer and
interfaces’). Please note, that the complete script editor is printed out, not only the visible part.
4.4.4.4 Speed and torque calculation (option MotorTorque-SOFT)
This option provides two functions which calculate the values speed and torque from motor
current and voltage. The motor must be a three phase asynchronous standard motors according
IEC. There are just some information from type plate or catalogue data necessary. There is no
need of a torque measuring shaft or a speed sensor. The motor can be connected to the lines or
to a frequency converter.
Measuring error between no-load operation and 1.5 fold nominal torque typical below 2% of
nominal torque resp. rotation speed for motors from 1kW to 100kW nominal power and
rotation speed between -40% to +20% of nominal speed. The calculation is also possible with
other nominal power, but with increased error.
For the calculation, following requirements must be met:
•
Wiring
3+1, U
∆
I*->U*I*
•
Filter
Smaller than half clock frequency. So just the fundamental must be measured, the clock
ripple must be rejected.
•
Signal coupling
AC
•
Sync
Such, that the fundamental frequency is displayed (e.g. I1, LP<300Hz)