PDUS210 – 210 Watt Ultrasonic Driver / Generator

The PDUS210 is a complete solution for driving precision and high-power ultrasonic actuators. The amplifier includes high-speed resonance and anti-resonance tracking, current or voltage set points, 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 parallel resonance which is characterized by higher voltage but lower current and lower actuator heating.

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 and Amplitude Control

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 above or below resonance, which may provide higher immunity to load variations. Systems with low quality factor may have phase responses that are non-zero at resonance. In such cases, an impedance response should be performed to identify the desired operating phase.

Ultrasonic frequency response
Ultrasonic actuator impedance

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 $\theta_{ref}$.

Ultrasonic frequency control loop

Phase control loop in the PDUS210 driver.

When operating at the series resonance, the vibration amplitude is approximately proportional to the actuator current. Therefore, to minimize sensitivity to load variations, the RMS current should be held constant. To achieve this, the PDUS210 can be operated with either voltage or current set points.

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, so constant voltage excitation is most commonly used. 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.

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 voltage ranges
Output Current Max 0 – 32 Ap-p See standard voltage ranges
Optimal Load Impedance 1.5 – 400 Ohms See standard voltage ranges
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 6kHz to 500kHz with modification
Power Supply 48 V, 280 Watt
Controller Phase tracking, current control, power control 2ms frequency update rate
Resonance or anti-resonance
Interface USB, RS485 RS232 possible
Digital IO 4 DIO For manual control
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

Standard Voltage Ranges

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

Note: The output voltage resolution and tolerance is 8 bits, or 256 levels. Therefore, the smallest possible change in voltage is FSR / 256, where FSR is the full scale range in any units. The minimum output voltage is also limited by resolution. When the amplifier is enabled and the output voltage is set to zero volts, the actual output voltage may be up to 1% of FSR.

The relationship between maximum achievable power and the load impedance is plotted in the following figure. In this plot, the impedance is normalized to the optimal impedance. For example, the optimal impedance of the PDUS210-400 is 100 Ohms. From the plot, it can observed that greater than 100 W can be achieved with a normalized impedance from 0.65 to 2.1, which for the PDUS210-400, is 65 Ohms to 210 Ohms.

PDUS210 Maximum ultrasonic power versus normalized impedance

Maximum output power versus normalized impedance

The impedance ranges for other common power levels are listed in the following table. For example, all amplifiers will supply more than 150W with a normalized load impedance between 0.71 and 1.4. For the the PDUS210-400, this is equivalent to 71 Ohms and 140 Ohms.

Minimum Power Z Low Z high
150 W 0.71 1.4
100 W 0.65 2.1
50 W 0.53 4.2

Range of normalized load impedance versus output power

Front Panel

PDUS210 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

PDUS210 Rear Panel
Remote Control Digital Input-Output Connector (D-SUB9 Connector). The pinout is:

  1. 3.3V Supply
  2. In1 (3.3V to 24V logic, max 30V)
  3. In2 (3.3V to 24V logic, max 30V)
  4. Out1 3.3V logic (24V output optional)
  5. Out2 3.3V logic
  6. GND
  7. 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:

  1. Not Connected
  2. Receive In
  3. Transmit Out
  4. Not Connected
  5. Isolated Ground

Overload Protection

There are three types of overload protection:

Hardware Overload
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.

Load Power Dissipation Overload
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.

Amplifier Power Dissipation 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.

Thermal Overload
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.

An example script for Python (example.py) can be found at 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

Standard Delivery Contents

  • PDUS210 amplifier with chosen configuration e.g. PDUS210-800
  • Power supply, 280W 48V, Meanwell GST280A48-C6P
  • IEC C13 Mains power cable suitable for the shipping destination
  • USB Cable, Type A to Type B, 3 foot.
  • 2 x Three-way Plug-in screw terminal connectors (Amphenol TJ0331530000G, or similar)
  • 1 x Four-way Plug-in screw terminal connectors (Amphenol TJ0431530000G, or similar)

Certifications

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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