Sine-Wave Filters - Siemens SINAMICS G130 Engineering Manual

Fundamental Principles and System Description
Engineering Information
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Sine-wave filters

Sine-wave filters are LC low-pass filters and constitute the most sophisticated filter solution. They are significantly
more effective than dv/dt filters plus VPL in reducing the voltage rate of rise dv/dt and peak voltages V
operation with sine-wave filters imposes substantial restrictions in terms of the possible pulse frequency settings and
utilization of the inverter current and voltage.
As the schematic sketch below illustrates, the sine-wave filter filters the fundamental component output of the inverter
pulse pattern. As a result, the voltage applied to the motor terminals is sinusoidal with an extremely small harmonic
content.
Schematic sketch of the voltage v(t) at the inverter output and motor terminals with a sine-wave filter
Sine-wave filters very effectively limit both the rate of voltage rise dv/dt and the peak voltage V
winding to the following values:
•
Voltage rate of rise dv/dt << 50 V/μs
•
Voltage peaks V
As a result, the voltage stress on the motor winding is virtually identical to the operating conditions of motors directly
connected to the mains supply. Bearing currents are also reduced significantly. Using these filters therefore allows
standard motors with standard insulation and without insulated bearing to be operated on SINAMICS. This applies to
both Siemens motors and motors supplied by other manufacturers.
Due to the very low voltage rate of rise on the motor cable, the sine-wave filter also has a positive impact in terms of
electromagnetic compatibility which means that it is not absolutely essential to use shielded motor cables to achieve
the required standard of EMC.
Since the voltage applied to the motor is not pulsed, the converter-related stray losses and additional noise in the
motor are also reduced considerably and the noise level of the motor is approximately equivalent to the level
produced by mains-fed motors.
Sine-wave filters are available
•
in the 380 V to 480 V voltage range up to a converter rated output of 250 kW at 400 V,
•
in the 500 V to 600 V voltage range up to a converter rated output of 132 kW at 500 V,
To make allowance for the resonant frequency of the filter, the pulse frequency setting for drives with sine-wave filters
is fixed at 4 kHz (380 V – 480 V) or at 2.5 kHz (500 V – 600 V).
For this reason, the permissible output current is reduced to the values given in the table.
SINAMICS Engineering Manual – May 2008
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© Siemens AG
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