Siemens SINAMICS S120 System Manual page 131

● Corresponding to the selected configuration, the signal sources for the current and
voltage actual values must be parameterized for the cosφ measuring point in p3473 and
p3474.
● The measured value is displayed as amount (r3478) and sign (r3477). Especially for
r3478 = 1, even minimum phase shifts of the currents cause the sign to change. Suitably
selecting the smoothing p3476 can prevent undesirable toggling and/or ensure the
required response time of the measurement.
● Taking into account all dead times and delay times in the current and voltage
measurement is decisive regarding the accuracy of the cosφ display. The measurement
can be adapted using p3479 if a VSM10 is not used to measure the current, or additional
dead times occur as a result of the communication buses.
The cosφ calculation can be simply calibrated without using external measuring devices
by simultaneously using both cosφ displays. The first display r3478[0] uses the current
measurement in the Active Line Module as well as the VSM10 voltages at the grid filter.
The second display r3478[1] uses the application-specific external measurement of the
same currents between the Active Line Module and Active Interface Module, as well as
the same VSM10 voltages in 3-conductor coordinates:
– p3473[0] = r3467[2],
– p3473[1] = r3467[3],
– p3474[0] = default,
– p3474[1] = default,
– p3475[0] = 1,
– p3473[2] = e.g. r5471[0],
– p3473[3] = e.g. r5472[0],
– p3474[2] = r3661,
– p3474[3] = r3662,
– p3475[1] = 3.
When dead time p3479[1] is correctly set, the displays of r3478[0] and r3478[1] are the
same in operation.
Calibration accuracy can be increased when required by using separate external
reference measuring devices.
Calibration parameter p3479 is preset for current measurement with the 10 V inputs of
the VSM10. When correctly calibrated, the cosφ display error is typically <0.01.
Grid infeed
System Manual, 04/2015, A5E03347436A
Commissioning
7.9 Commissioning cos phi display
131