SA Stack Actuators
150V Piezoelectric Stack Actuators
|Prod. Model||Range +/-10%||Lgth||Cross Sect||Cap. +/-20%||Mass||Block Force||Stiff.||Res. Freq.|
The PiezoDrive SA stack actuators are high performance multilayer stack actuators with a vacuum compatible polymer coating for improved reliability and protection against dust and humidity. PiezoDrive actuators are designed for applications that require long range, high force, nanometre resolution, and high speed. The SA actuators are perfectly matched to the range of PiezoDrive amplifiers and driver modules. Applications include: Nanopositioning, Microscopy, Precision Machining, Vibration Control, Hydraulic Pumps, Valves, and Optics.
Stack actuators should not be exposed to significant tensile loads, unequally distributed loads, off-axis loads, bending moments, or torque. To reduce mounting errors, a ceramic or stainless steel ball end can be used to interface the stack actuator to the load. Flexural mechanisms are also recommended.
The maximum recommended tensile load is 10% of the blocking force. In applications that require bi-directional forces or high speed motion, a preload force is recommended with a magnitude greater than the maximum tensile load. This gaurantees that the actuator is always in compression. The maximum recommended preload is 50% of the blocking force.
PiezoDrive stack actuators can be supplied with Saphire ball ends to improve the load distribution, simplify the mounting, and reduce bending moments during service. One or two ball ends can be specified by adding -1BE, or -2BE to the order code. E.g. SA070718-2BE.
|Actuator Width||Ball End Diameter||Additional Length|
|3 mm||3 mm||3 mm|
|5 mm||5 mm||5 mm|
|7 mm||6.5 mm||6.5 mm|
The range is specified for an applied voltage of -30V to +150V. If the input voltage is unipolar (0V to +150V) the specified range is reduced by a factor of 0.75. When a stack actuator is driving a stiff spring, the range is reduced by the factor.
where kp is the actuator stiffness and kL is the load stiffness.
The travel range can also be reduced by restraining the end plates, e.g. by bonding the actuator to a stiff base. This effect is most significant in actuators that have a length less than twice the width.
The actuator capacitance is the small-signal capacitance measured at room temperature. Due to hysteresis, the effective capacitance increases with applied voltage. When operating at full range, the effective capacitance is approximately twice the small-signal capacitance. The capacitance also increases with temperature. A temperature increase of approximately 50 degrees C will double the effective capacitance.
Piezoelectric actuators dissipate heat when driven at full range with a high frequency. PiezoDrive actuators can be operated continuously at temperatures up to 85 degrees C. Continuous operation beyond this temperature may damage the actuator.
The dissipated heat is approximately 10% of the applied electrical power. For a sine-wave, the applied electrical power is:
Electrical Current Requirements
The required current is I=C dV/dt where I is the current, C is the effective capacitance, and dV/dt is the voltage rate of change. For a sine-wave, the required peak current is equal to:
where Vp-p is the peak-to-peak voltage. For a triangle wave, the required peak current is equal to:
|PDm200B||General purpose, low cost|
|MX200||High Current, Low noise, low cost|
|PD200||High speed, low noise|
|PX200||High current, low noise|
All of the connecting wires are 100mm AWG26 PTFE insulated wires, except for the SA030306 actuator which has 15mm leads. Other lengths are available on request. Red identifies the positive terminal.
The SA Actuators are supplied with either vacuum compatible polymer encapsulation or a UV cured lacquer coating. Both coatings and the wiring insulation meet the outgassing requirements for NASA SP-R-0022A.
- Ceramic ball ends (Order suffix - 1BE or 2BE)
- Custom range and dimensions
- Custom wiring arrangement/connectors
- Preload or mechanical amplifier mechanisms
The total stack dimensions are based on the width and length of the ceramic listed in the specifications. The length specification includes the piezoelectric stack and two 1-mm thick ceramic end plates.
The piezoelectric material is similar to PZT-5H and Navy Type VI.