Siemens SINAMICS G130 Engineering Manual page 18

Fundamental Principles and System Description
Engineering Information
Influence of the pulse frequency on motor noise
A higher level of magnetic motor noise is excited when three-phase motors are operated on PWM converters. This is
caused by the voltage pulsing which results in additional voltage and current harmonics.
According to DIN VDE 0530 or IEC 60034-17 "Rotating electrical machines / Squirrel-cage induction motors fed from
converters - Application guide", the A-graded noise pressure level increases in the order of magnitude of between
5 dB and 15 dB when three-phase motors are operated on a PWM converter up to rated frequency as compared to
motors of the same type operating on sinusoidal voltage at rated frequency. The actual values depend on the PWM
method used, the pulse frequency of the converter and the design and number of poles of the converter-fed motor.
In the case of SINAMICS converters operating at the factory-set pulse frequency, the additional noise pressure level
produced by the motor as a result of the converter supply is in the order of magnitude of between 5 dB(A) and
maximum 10 dB(A).
A reduction of the additional motor noise caused by the converter supply can generally be achieved by an increase in
the pulse frequency. It can therefore be meaningful to raise the pulse frequency in order to attenuate the motor noise.
It must be noted that the inverter current may need to be reduced (derated) with an increased pulse frequency and
other limitations may apply with respect to motor-side options such as motor reactors, dv/dt filters plus VPL (Voltage
Peak Limiter) and sine-wave filters.
Correlation between pulse frequency and converter output frequency (fundamental wave frequency)
With space vector modulation, there is a fixed correlation between the pulse frequency and the maximum attainable
converter output frequency (fundamental wave frequency). The pulse frequency must be at least 12.5 times higher
than the required converter output frequency on SINAMICS converters. This means that the maximum achievable
output frequency at a given pulse frequency is limited according to the formula
f = f / 12.5
Converter max pulse
The table below shows the possible pulse frequency settings and the associated maximum achievable output
frequencies for converters and inverters with the factory set pulse frequencies f
pulse frequency setting scale is expanded with firmware version V2.4 and higher.
Units with factory setting f
Pulse frequency
2.0 kHz
4.0 kHz
8.0 kHz
-
Settable pulse frequencies and associated maximum attainable output frequencies on SINAMICS converters
Correlation between pulse frequency and motor-side options (motor reactor and motor filter)
If motor reactors, dv/dt filters plus VPL or sine-wave filters are installed at the motor output, the maximum permissible
pulse frequency and thus also the maximum output frequency are limited by these options. In some cases, a fixed
pulse frequency is specified:
•
Permissible pulse frequency with motor reactor (SINAMICS):
The maximum pulse frequency is limited to twice the value of the factory setting, i.e. to 4 kHz on units with
factory setting 2 kHz and to 2.5 kHz on units with factory setting 1.25 kHz. The maximum output frequency is
limited to 150 Hz independent of the selected pulse frequency.
•
Permissible pulse frequency with dv/dt filter plus VPL (SINAMICS)
The maximum pulse frequency is limited to twice the value of the factory setting, i.e. to 4 kHz on units with
factory setting 2 kHz and to 2.5 kHz on units with factory setting 1.25 kHz. The maximum output frequency is
limited to 150 Hz independent of the selected pulse frequency.
•
Permissible pulse frequency with sine-wave filter (SINAMICS):
Sine-wave filters are available for voltage levels 380 V to 480 V 3AC and 500 V to 600 V 3AC. The pulse
frequency is a mandatory fixed value and equals 4 kHz (380 V to 480 V) or 2.5 kHz (500 V to 600 V). The
maximum output frequency is limited to 150 Hz.
•
Permissible pulse frequency with sine-wave filter (external supplier):
The pulse frequency and maximum output frequency must be set according to the filter manufacturer's
instructions.
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(but a maximum of 300 Hz on asynchronous machines with vector control mode).
= 2.0 kHz
pulse
Max. output frequency
160 Hz
300 Hz
300 Hz
-
= 2.0 kHz or f
pulse
Units with factory setting f
pulse
Pulse frequency
1.25 kHz
2.50 kHz
5.00 kHz
7.50 kHz
= 1.25 kHz. The
pulse
= 1.25 kHz
Max. output frequency
100 Hz
200 Hz
300 Hz
300 Hz