Siemens SINAMICS G130 Engineering Manual page 14

Fundamental Principles and System Description
Engineering Information
The following diagram illustrates how the voltages in phases L1 (R) and L2 (S) plus output voltage V
phase voltage) are produced by the method of pulse width modulation and shows their basic time characteristics. The
frequency with which the IGBTs in the inverter phases are switched on and off is referred to as the pulse frequency or
clock frequency of the inverter.
Timing of the gating signal sequence for the IGBTs of the two inverter phases L1 (R) and L2 (S) plus the associated output
voltage V (V- phase-to-phase). The amplitude of the voltage pulses corresponds to the DC link voltage.
RS
The diagram below shows the time characteristic (in red) of the inverter output voltage (phase-to-phase voltage) and
the resulting current (in black) generated in the motor when a standard asynchronous motor with a rated frequency of
50 Hz or 60 Hz is used and the inverter is operating with a pulse frequency of 1.25 kHz. The diagram shows that the
smoothing effect of the motor inductances causes the motor current to be virtually sinusoidal, despite the fact that the
motor is supplied with a square-wave pulse pattern.
Motor voltage (phase-to-phase) and motor current with space vector modulation
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© Siemens AG
(phase-to-
RS