6 – 196 HEIDENHAIN Technical Manual TNC 426, TNC 430
6.12.5 Volts-per-Hertz Control Mode
In volts-per-hertz control mode (U/f control mode), the motor is speed-controlled
in an open loop. The motor voltage increases in proportion to frequency up to the
break (= threshold rpm for field weakening). Then the motor voltage remains
constant (= rated voltage of motor); only the frequency continues to increase.
Maximum speed in U/f control mode:
n with an integral spindle DSP:
n without an integral spindle DSP:
Volts-per-hertz control mode is only possible on the TNC 426 M and
TNC 430 M. The following PWM outputs may be used:
n TNC 426 M with spindle DSP, TNC 430: X61
n TNC 426 M without spindle DSP: X55, X56
To drive a motor with a U/f component:
7
77
7 In the motor table, enter for your motor in the column Motor model (TYPE)
UASM, in the column Encoder line count (STR.) the value 0, in the column
Type of encoder (SYS) the value 0 and in the column Maximum temperature
[°C] T-MAX the value 255.
7
77
7 The machine parameters for current controller (MP24xx) and speed
controller (MP25xx, MP 26xx) are nonfunctional.
7
77
7 The acceleration and breaking ramp (MP341x) must be set so that the
maximum current is not exceeded.
Since during volts-per-hertz (U/f) control mode no speed encoder is used,
W322 = 0 (actual speed value) supplies the value 0:
7
77
7 Module 9164 can determine the actual speed value while the spindle is
running, but not during the acceleration and braking phases.
U
M
f
M
f
break
U
N
60000
No. pole pairs
-------------------------------------------
rpm
24000
No. pole pairs
-------------------------------------------
rpm
Note
n If the maximum current is exceeded, the inverter switches off and the
spindle coasts to a stop.
n The oscilloscope shows the actual current instead of the nominal current
(I NOML), since there is no nominal current with U/f components.
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