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.

PDUS210_mechanical_responce
PDUS210_electrical_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 $\theta_{ref}$.

PDUS210_control_loop_phase

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.

PDUS210_control_loop_power

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

1232Asset 1
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
Volt Mon Output current monitor, AC Coupled
Current Mon Output voltage monitor, AC Coupled
Lemo HV Output Suits LEMO 0B.302 Connector
Screw HV Output Suits Amphenol TJ0331530000G Connector

Rear Panel

1dfsdAsset 1
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

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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