# PDUS210 – 210 Watt Ultrasonic Driver

The PDUS210 is a complete solution for driving precision and high-power ultrasonic actuators. The amplifier includes high-speed resonance and anti-resonance tracking, power control, and functions such as impedance and frequency response analysis. The PDUS210 is well suited to both OEM product integration and laboratory use for research and development. Applications include ultrasonic drilling and cutting, medical devices, dental devices, ultrasonic testing, liquid cavitation, and vaporization.

The PDUS210 is controlled via USB and the included software package. An RS485 interface also provides a straight-forward method to control and monitor the amplifier for automatic test and OEM applications.

The PDUS210 generates a pure sine-wave output which avoids the excitation of secondary resonance modes by the drive harmonics. This makes it ideal for operating at the electrical parallel resonance, or “anti-resonance”. This operating point is close to the mechanical resonance frequency but is less sensitive to changes in load dissipation, which is useful in precision machining applications where constant vibration amplitude is desired.

The PDUS210 is available with standard output voltage ranges from 17 Vrms to 282 Vrms, and current ranges from 0.7 Arms to 11 Arms. These ranges are optimized for load impedances ranging from 1.5 Ohms to 400 Ohms at resonance.

### Ultrasonic Drive Methods

For an introduction to driving ultrasonic transducers, refer to Introduction to Ultrasonic Drivers

### Resonance Tracking

The following figure plots the mechanical and electrical frequency response of an ultrasonic transducer. The impedance minima at $f_{s}$ is known as the series resonance, which is approximately equal to the mechanical resonance frequency. At this frequency, the phase response has a high slope and value of zero degrees. Resonance tracking is achieved by varying the drive frequency to regulate the phase to zero. Alternatively, the phase set point can be selected to operate slightly above or below resonance, which may provide higher immunity to load variations at the expense of electrical efficiency. Furthermore, systems with low quality factor may have phase responses that are non-zero at resonance, particularly for the parallel resonance. In such cases, an impedance response should be performed to identify the desired operating point.

Electrical and mechanical response of an ultrasonic transducer.

The resonance tracking system of the PDUS210 is described in the diagram below. A phase detector (M) measures the impedance phase angle between the primary voltage and current. The phase controller $C_{\theta}(s)$ varies the drive frequency to maintain a constant phase set point $\theta_{ref}$.

Phase control loop in the PDUS210 driver.

The electrical response also exhibits an impedance maxima, known as the parallel resonance. At this frequency the applied voltage is approximately proportional to the vibration amplitude. This operating mode is advantageous in applications that require constant vibration amplitude.

Phase tracking at the parallel resonance is identical to the series resonance, except for the opposite slope of the phase curve, which requires a negative controller gain. Any positive phase controller gain will track a series resonance mode, while any negative controller gain will track a parallel resonance mode.

### Power Control

While operating with constant vibration amplitude, there is no control over the power dissipated by the transducer, or delivered to the load. However, limits can be set on the maximum power dissipation regardless of the operating mode.

In many applications it is desirable to directly regulate the load power since this is proportional to parameters such as work-piece heating and cavitation. As shown in the diagram below, the power control loop varies the excitation voltage to maintain a constant load power. In applications such as ultrasonic machining where the tool is intermittently in and out of contact with the work piece, the power control loop is best disabled while the tool is unloaded. Power control is most effectively combined with constant current excitation while operating at series resonance, or constant voltage excitation when operating at parallel resonance.

Phase and power control loop in the PDUS210 driver.

### Choosing the Voltage Range

The PDUS210 is available in voltage ranges from 17 Vrms to 282 Vrms, which correspond to impedances ranging from 1.5 $\Omega$ to 400 $\Omega$ . The optimal choice is determined by the transducer impedance at resonance, and the choice of series or parallel resonance.

The first step is to measure the impedance of the transducer at the series and parallel resonance. This can be performed with an impedance analyser or simply a signal generator and oscilloscope. If possible, these tests should be performed at moderate power with both minimum and maximum load conditions. Fill out the values in the table below:

 Unloaded Fully Loaded Series Resonance $R_{1,min}$: $R_{1,max}$: Parallel Resonance $R_{2,max}$: $R_{2,min}$:

Table of operating impedance at resonance.

Series Resonance
For operation at the series resonance, the most suitable amplifier has an optimal impedance which is close to, or slightly greater than the fully loaded impedance. Since transducer impedance tends to increase with applied power, an amplifier with a higher optimal impedance is recommended. If the amplifier has a higher optimal impedance than the load, the current limit will be reached before the voltage limit, and the maximum achievable output power is:
$$P = I^{2}_{rms}R_{1,max}$$ where $I_{rms}$ is the maximum driver current.

Parallel Resonance
For operation at the parallel resonance, the most suitable amplifier has an optimal impedance which is close to, or slightly less than the fully loaded impedance. Since transducer impedance tends to reduce with applied power, an amplifier with a lower optimal impedance is recommended. If the amplifier has a lower optimal impedance than the load, the voltage limit will be reached before the current limit, and the maximum achievable output power is:
$$P = \frac{V^{2}_{rms}}{R_{2,min}}$$ where $V_{rms}$ is the maximum driver voltage.

Custom Voltage Range
Custom voltage ranges and optimal impedances are available to provide maximum power for a specific transducers.

### Specifications

 Electrical Specifications Specification Value Notes Output Voltage 0 – 800 Vp-p See standard load configurations Output Current Max 0 – 32 Ap-p See standard load configurations Optimal Load Impedance 1.5 – 400 Ohms See standard load configurations Output Waveform Sine wave DC Output Voltage Zero DC offset possible Output Isolation Isolated or grounded Max Output Power 210 W With optimal load impedance Internal Power Dissipation 130 W Maximum Frequency 20 – 200 kHz 5kHz to 500kHz possible Power Supply 48 V, 280 Watt Controller Phase tracking and power control 2ms frequency update rate Resonance or anti-resonance Interface USB, RS485 RS232 possible Digital IO 4 DIO For manual control
 Output Voltage Range Order Code Max Voltage Volts pk-pk Max Voltage Volts RMS Max Current Amps pk-pk Max Current Amps RMS Optimal Load Ohms PDUS210-800 800 282 2 0.71 400 PDUS210-600 600 212 2.6 0.92 225 PDUS210-400 400 141 4 1.4 100 PDUS210-200 200 70 8 2.8 25 PDUS210-100 100 35 16 5.7 6.25 PDUS210-50 50 17 32 11.3 1.56
 Mechanical Specifications Specification Value Notes Enclosure Dimensions 227 x 168 x 54 mm L x W x H Mass 1.4 kg Temperature Range 0C – 50C Humidity Non-condensing

### Front Panel

 ON Power indicator OVL Indicates an overload or shutdown state, see overload protection USB USB 2.0 Type-B device connector L1 Uncommitted LED indicator L2 USB Activity indicator RS485 Isolated RS485 interface, GND is the remote ground Test +/-4V Input produces full-range output voltage. Test use only. Aux Connected to ADC converter, not presently used Current Monitor Output current monitor, AC Coupled. The gain is $0.00264 \times V_{pp}$ V/A Voltage Monitor Output voltage monitor, AC Coupled. The gain is $5.06/V_{pp}$ V/V Lemo HV Output Suits LEMO 0B.302 Connector Screw HV Output Suits Amphenol TJ0331530000G Connector

The sensitivity of the current and voltage monitors are determined by the peak-to-peak output voltage range. For example, the peak-to-peak output voltage range of the PDUS210-400 is 400, so the current gain is 1.056 V/A, and the voltage gain is 0.01265 V/V.

### Rear Panel

 Remote Control Digital Input-Output Connector (D-SUB9 Connector). The pinout is: 3.3V Supply In1 (3.3V to 24V logic, max 30V) In2 (3.3V to 24V logic, max 30V) Out1 3.3V logic (24V output optional) Out2 3.3V logic GND GND Power 1 Suits Amphenol TJ0331530000G Connector Power 2 Suits 6-Pin power connector for Meanwell GST280A48-C6P RS232 Isolated RS232 serial port. Uses same isolated supply as RS485, do not use both simultaneously (D-SUB9 Connector). The pinout is: Not Connected Receive In Transmit Out Not Connected Isolated Ground

There are three types of overload protection:

This overload is triggered when the current to the power amplifier exceeds 5.7 Amps average. When triggered, the power amplifier is shutdown, causing the “Overload” front panel LED to illuminate. To restart the amplifier, an enable command is required.

At power-on, the power amplifier is shutdown by default and requires an enable command to start.

This overload is triggered when the real power dissipated by the load exceeds the threshold defined in the user interface. An enable command is required to clear this overload.

This overload is triggered when the real power dissipated by the power amplifier exceeds 100 Watts. An enable command is required to clear this overload. Triggering this overload usually means that the load impedance is poorly matched to the output voltage and current range of the amplifier.

This overload is triggered when the heatsink temperature exceeds 70C. An enable command is required to clear this overload. Check the fan and heatsink for blockages.

### Desktop Software

Overview

Frequency Sweep Overview

To Track a Resonance

Power Tracking

### RS485 Interface

RS485 is a two-wire communication standard, commonly used for industrial machine-to-machine, and computer-to-machine communications (Introduction to RS485).

The PDUS210 responds to the commands described in https://github.com/PiezoDrive/RS485-API

For testing purposes or to control the amplifier from a PC, an RS485 USB cable is required, for example, FTDI USB-RS485-WE-1800-BT. The connection diagram below is recommended. A text based application such as Putty can be used to send or receive commands.

 Baud Rate 9600 Data Bits 8 Stop Bits 1 Parity None

USB-RS485-WE-1800-BT Cable

### Warranty and Service

The PDUS210 is guaranteed against manufacturing defects for 12 months from the date of purchase.
Contact your distributor or info@piezodrive.com for service. Please include the amplifier serial number.

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