Functions 09.2008
6SE7087-6QX70 (Version AK) Siemens AG
7-72 Compendium Motion Control SIMOVERT MASTERDRIVES
7.3.10 Harmonic compensation
This function is designed to compensate for torque ripple which has a
functional correlation with an angular signal. This signal can be defined,
for example, by the rotor position, the electrical angle or the angle of
the external encoder. Torque ripple can also occur as a result of the
specific design of a motor.
For torque ripple to be reduced effectively with this function, the ripple
must exhibit the following properties:
♦ Frequency of the ripple must be a multiple of the input signal
frequency
♦ Fourier decomposition of the torque ripple signal must indicate a
dominant harmonic
This function is capable of compensating for two of the dominant
harmonics identified by Fourier decomposition.
For this purpose, a signal in phase opposition is injected in the torque
setpoint channel. The time response of the compensation signal is
configured by means of the following parameters.
P309: Order of harmonic to be compensated (referred to electric
fundamental wave)
(Index 1 – 1st harmonic, index 2 – 2nd harmonic)
P310: Phase angle of harmonic (sine) referred to the start point of the
fundamental wave (sine) in phase U with a clockwise phase
sequence
(Index 1 – 1st harmonic, index 2 – 2nd harmonic)
The time response of the compensation signal defined by these
parameters is mapped at connector K0272.
The severity of the torque ripple can vary as a function of the motor
current. The variation in the compensation signal amplitude can be
quantified in the two parameters below using a square-law growth
function.
P311: Maximum current, i.e. current with maximum torque ripple
P312: R.m.s. value of compensation signal for
P312.1 I
tot
= 0 % * P311
P312.2 I
tot
= 50 % * P311
P312.3 I
tot
= 100 % * P311
(indices 4-6 analogous for 2nd harmonic)
A square-law interpolation calculation is performed between the three
interpolation points. The signal value of the resulting compensation
signal is mapped at connector K0273.
The compensation signal is injected as current upstream of the current
limiter. This means that the configuration must allow for the functional
correlations between torque ripple and compensation current.
The harmonic compensation function block is described in FD630.
Description
Parameters
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