HEIDENHAIN MANUALplus 620 Technical Manual page 938

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6.16.25 Speed-dependent switching of the PWM frequency

This function is only available when using the CC 61xx, UEC 11x or CC 424

controller unit!

Settings in the configuration editor

ParameterSets

[Key name of the parameter set]

CfgServoMotor

motSpeedSwitchOver

motSpeedSwitchBack

This function is used with high-speed spindle drives. This switchover is only

possible for double-speed control loops. (Software option)

In MP_motSpeedSwitchOver and MP_motSpeedSwitchBack, a speed-

dependent hysteresis for switching the PWM frequency is specified. It only

takes effect if the value in MP_motSpeedSwitchBack is less than the value

in MP_motSpeedSwitchOver.

This function is associated with MP_iCtrlPwmType and MP_iCtrlPwmInfo.

Only if MP_iCtrlPwmType = 2, and MP_ampPwmFreq ≤ 5 kHz, does the

switching of the PWM frequency take effect. Please note that the adjustment

of the current controller (MP_iCtrlPropGain, MP_iCtrlIntGain) is based on

the lower PWM frequency ≤ 5 kHz. Adaptation of the current-controller

parameters and consideration of the power-module derating are performed

automatically.

Using this function provides several benefits:

At lower speeds and therefore a lower PWM frequency, the power module

provides a comparatively high current. This results in a relatively high

maximum motor torque.

On the one hand, losses due to harmonics in the motor become more

important as the speed increases, and on the other hand, the relationship

between the electrical frequency and the PWM frequency worsens. These

two disadvantages can be counteracted by increasing the PWM frequency.

The resulting reduction of the current normally is insignificant, since in part

due to motor characteristics, very high motor currents are mostly no longer

possible or needed at higher speeds.

The speed-dependent switching of the PWM frequency is only permitted

with power modules from HEIDENHAIN.

Speed-dependent switching of the PWM frequency with non-HEIDENHAIN

power modules can lead to malfunctions, and possibly to damage of the

power modules. Therefore, only use this function with power modules

from HEIDENHAIN.

HEIDENHAIN Technical Manual MANUALplus 620