Table of Contents
Advertisement
12 Control of Vibration Amplitude
Power ultrasonic applications can be categorized as either constant mechanical load, or variable
mechanical load. The requirements for both cases are described in the following.
12.1 Constant Mechanical Load
Constant load applications are the simplest case and include, for example, ultrasonic cleaners,
ultrasonic mixers, and any other application where the mechanical load does not vary significantly.
These applications can be operated with constant voltage at either the series or parallel resonance.
12.2 Variable Mechanical Load
Applications with variable mechanical load include ultrasonic drills and cutters where the mechanical
load conditions vary during operation. These applications generally require some form of amplitude
control to maintain vibration amplitude when the mechanical load dissipation increases; and to avoid
vibration amplitude increasing when the mechanical load dissipation is reduced.
To achieve approximately constant vibration amplitude, a transducer can be driven with constant
voltage at the parallel resonance frequency, or constant current at the series resonance frequency.
Constant voltage is the natural operating mode of the PDUS210 but constant current can also be
achieved by enabling the current tracking mode. The operation of current tracking mode is illustrated
in Figure 6. Current tracking mode has the same frequency control loop as Figure 5 but also has an
additional feedback loop that varies the voltage to maintain a constant load current. The current set
point is ��
and the controller is ��
.
������
��
Current tracking mode is most useful for achieving constant vibration amplitude in transducers
operated at the series resonance mode (impedance minima).
Phase
Frequency
Signal
Power
Transformer
Setpoint
Controller
Generator
Amplifier
Transducer
Ground
Connection
Phase and Current Detector
Figure 6. Phase and current control loop in the PDUS210 driver.
PDUS210 V5 Manual
12
Modified 17/12/2022
Advertisement
Table of Contents
