Piezoelectric Actuators - General Information
To ensure reliability in service, the multilayer actuators
are comprehensively tested under the following conditions:
|
Test
|
Conditions
|
Level
|
| Displacement |
At
max operating voltage |
AQL |
Capacitance
& Tan |
120Hz,
1Vrms |
100% |
| Insulation
Resistance |
At
max operation & voltage |
100% |
Handling
Multilayer actuators are made of ceramic and may be damaged
if subjected to excessive physical or thermal shock.
Operating
Environment
As voltages of up to 300 V (d.c.) may be employed, it is
necessary to ensure that the actuators do not come into
direct contact with moisture. Never use high voltages in the
vicinity of inflammable liquids or gasses.
Mounting
Multilayer Actuators
Devices may be attached using an epoxy resin adhesive that
cures at temperatures below 75°C. To obtain maximum
displacement and stiffness from the actuator, the bond
thickness should be minimised. The mounting fixture must be
designed to ensure that no shear or tensile stresses are
placed on the actuator. It is preferable that the actuator
is always compressively stressed.
Driving
of Multilayer Actuators
During the manufacture of these devices, a d.c. voltage is
applied to polarize the ceramic (analogous to the
magnetization of magnets). Either d.c. or a.c. Voltage can
be used, although the voltage should not be greater than 1/8
the rated voltage in reverse polarity, in order to avoid
polarization
switching. In order to permit driving of the actuator under
an a.c. field without the polarization direction switching,
a d.c. bias field may be applied in the positive direction.
The use of a.c. driving signals will induce a temperature
rise, which will increase as a function of frequency. The
temperature rise must be controlled to avoid the heating
beyond 75°C. As multi-layer actuators have a relatively
large capacitance, the upward response time depends upon the
current rating of the power supply. For a rapid downward
response, the discharging of the actuator is rate
controlling. The maximum charging / discharging current must
not exceed 5 Amps.

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