HEIDENHAIN TNC 426 PB/M Technical Manual page 798

6 – 468
Note
A reduction of the PWM frequency has no effect on the maximum speed,
but it means that the axis and the spindle without integral DSP must be
commissioned again.
For the commissioning of new machines, HEIDENHAIN recommends
adjusting the PWM frequency to fit axis modules (normally 4 kHz, see
SIEMENS documentation). If the power module of the spindle gets too warm
in spite of a reduction of the PWM frequency from 5 kHz to 4 kHz, then the
reference value for the I
be reduced.
Reduction of the reference value for the I
current I
N
The reduction of the rated current I
2
datum value for I t monitoring can be calculated from two values (X1, X2) that
are given in the SIEMENS documentation.
The percent reduction of the rated current can be calculated with the following
formula:
X [%] = 100
R
n
X1 = Reduction factor of the current in % at a PWM frequency of 8 kHz
n
X2 = PWM threshold frequency in kHz at which the electrical power
reduction begins
n
f = PWM frequency in kHz set in MP2180.0-8
PWM
This results in the reference value for I
X [%]
R
X = 1 ------------------- -
–
B
100
Example for a 50-A power module:
n
Axis power module with 50 A, PWM frequency of 5 kHz, X1 = 40 %, X2 =
4 kHz
(
æ
100 40
X [%] = 100 – --------------------------------------------------------------------------------------- -
è
R
15
X B = 1 ----------- = 0 85 ,
–
100
n
Spindle power module with 50 A, PWM frequency of 5 kHz, X1 = 40 %, X2
= 3.2 kHz
(
æ
100 40
X [%] = 100 – --------------------------------------------------------------------------------------- -
è
R
22,5
X B = 1 – ------------- = 0.78
100
2
t monitoring (MP2303) or the rated current I
2
t monitoring or the rated
of the power modules, as well as the
N
( ) 8 kHz f ⋅ (
100 X1
–
æ
------------------------------------------------------------------------------------------- -
–
è
8 kHz X2 –
2
t monitoring:
) 8 kHz 5 kHz ⋅ ( )
– –
8 kHz 4 kHz
–
) 8 kHz 5 kHz ⋅ ( )
– –
8 kHz 3,2 kHz –
HEIDENHAIN Technical Manual TNC 426, TNC 430
N
)
–
ö
PWM
+ X1
ø
ö
+ 40 = 15 %
ø
ö
+ 40 = 22,5 %
ø
must