Abstract
The switching frequency of the power electronics in servo drives significantly impacts its power dissipation and process accuracy. To date, a constant high switching frequency is typically used, based on the strictest requirements of the manufacturing process. The novel adaptive PWM approach dynamically adjusts the switching frequency at runtime to reduce switching losses of the power electronics, while maintaining the required process accuracy. The switching frequency is set based on the requirements of the active operating state of the tooling machine. To determine the optimal switching frequency, a holistic understanding of power dissipation in servo drives is required. A novel modulation-frequency-dependent power dissipation model, incorporating the losses in the drive amplifier and in the motor due to current ripple effects, is presented in this paper. The new model is validated over a wide range of parameters, including different motors, voltages and currents. The evaluation of the model results in a better understanding of the modulation-frequency-dependent power dissipation in servo drives and enables the determination of the optimal PWM frequencies. It is shown that higher energy savings can be achieved at higher voltages, while current ripple effects limit the effectiveness of the adaptive PWM approach for motors with lower power ratings.
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