Dr Kesorn Pechrach Weaver: Piezoelectrics in Circuit Breakers: Piezoelectric Actuators

Dr Kesorn Pechrach Weaver: Piezoelectrics in Circuit Breakers: Piezoelectric Actuators: Piezoelectric Actuators The planar disposition of the two ceramic plates means that the high fields can be applied without danger of re...

Piezoelectric Actuators

Piezoelectric Actuators

The planar disposition of the two ceramic
plates means that the high fields can be
applied without danger of repolarising the
ceramic. This is different from a
conventional bimorph structure.

The first arm of the actuator produces a
downward movement which provides an
angle for the movement amplification of the
second arm. The total movement is slightly
less than could be obtained from a single
beam of twice the length.

Ref: Piezoelectrics in Circuit Breakers: Design & Test

Dr Kesorn Pechrach Weaver: Piezoelectrics in Circuit Breakers: Arc current at 5.5 m/s

Dr Kesorn Pechrach Weaver: Piezoelectrics in Circuit Breakers: Arc current at 5.5 m/s: Arc current at 5.5 m/s The total period of the arc for the contact opening velocity at 5.5 m/s is about 6000 μs. The peak of arc curr...

Arc current at 5.5 m/s

Arc current at 5.5 m/s

The total period of the arc for the contact
opening velocity at 5.5 m/s is about 6000 μs.
The peak of arc current is about 2400 A. This
is higher than the arc current at contact
opening velocity of 10 m/s.

Ref: Piezoelectrics in Circuit Breakers: Design & Test

Dr Kesorn Pechrach Weaver: Piezoelectrics in Circuit Breakers: Opportunity: direct electromechanical coupling of ...

Dr Kesorn Pechrach Weaver: Piezoelectrics in Circuit Breakers: Opportunity: direct electromechanical coupling of ...: Opportunity The direct electromechanical coupling of a piezoelectric actuator means that it would be possible to tailor the contact ope...

Opportunity: direct electromechanical coupling of a piezoelectric

Opportunity

The direct electromechanical coupling of a
piezoelectric actuator means that it would be
possible to tailor the contact opening
trajectory simply by controlling the charge
on the actuator. It is known that the opening
velocity profile can have a significant effect
on the contact erosion [36, 37], and it may
therefore be possible to optimize the contact
opening trajectory for minimum contact
erosion. This is an important area for further
study.
These initial results show that despite a low
contact opening velocity on the
piezoelectrically operated contacts (due to
the large mass of the moving contact) the
transition to rapid arc motion away from the
contact region occurs only slightly later than
the constant velocity system. Clearly the
contact mass is a significant factor in the
speed of operation of the contact system.

Ref: Piezoelectrics in Circuit Breakers: Design & Test

Dr Kesorn Pechrach Weaver: Piezoelectrics in Circuit Breakers: How to Measure the Arc Pressure

Dr Kesorn Pechrach Weaver: Piezoelectrics in Circuit Breakers: How to Measure the Arc Pressure: How to Measure the Arc Pressure Two pressure transducers are used to monitor the gas pressure in the arc chamber. The SX series of pie...

How to Measure the Arc Pressure

How to Measure the Arc Pressure

Two pressure transducers are used to
monitor the gas pressure in the arc chamber.
The SX series of piezo resistive pressure
sensor functions as a wheatstone bridge on a
silicon chip with a response times of 0.1 ms.
The pressure transducer gives a voltage output directly proportional to the applied
pressure with sensitivity 0.75 mV/Psi. Long
term stability is 0.1% and repeatability is
0.5% (Maximum difference in output at any
pressure with the operating pressure range
and temperature within O °C to +70 °C).
Resistors are ion implanted into the silicon.
The cavity etched on the reverse to create a
thin silicon diaphragm.

Reference: Piezoelectrics in Circuit Breakers: Design & Test 

Dr Kesorn Pechrach Weaver: Piezoelectrics in Circuit Breakers: How to use Solenoid and Piezoelectric in Circuit B...

Dr Kesorn Pechrach Weaver: Piezoelectrics in Circuit Breakers: How to use Solenoid and Piezoelectric in Circuit B...: Solenoid and Piezoelectric in Circuit Breakers The waveform of arc voltage and contact position when the contact opening velocity of 1 ...

How to use Solenoid and Piezoelectric in Circuit Breakers

Solenoid and Piezoelectric in Circuit Breakers

The waveform of arc voltage and contact
position when the contact opening velocity
of 1 m/s, using solenoid and piezoelectric as
mechanism to open the contacts, as shown in
Figure 8.4.

From figure 8.5, on the 1 m/s moving
contact, the anode moves rapidly 2.5 mm
after 1 m/s at a contact gap of 0.6 mm, after
this movement the anode root remains static
for 2ms until the arc transfers rapidly away
from the contact region, at a contact gap of
2.5 mm.

Reference: Piezoelectrics in Circuit Breakers: Design & Test by Dr Kesorn Pechrach Weaver PhD

Dr Kesorn Pechrach Weaver: Piezoelectrics in Circuit Breakers: How to Achieve Satisfactory Short circuit Performa...

Dr Kesorn Pechrach Weaver: Piezoelectrics in Circuit Breakers: How to Achieve Satisfactory Short circuit Performa...: Achieve Satisfactory Short circuitPerformance   Miniature circuit breakers (MCBs) are widely used for protection from electrica...

Dr Kesorn Pechrach Weaver: Piezoelectrics in Circuit Breakers: Piezoelectric Arc Movement

Dr Kesorn Pechrach Weaver: Piezoelectrics in Circuit Breakers: Piezoelectric Arc Movement: Cathode Root Movement In Figure 8.6, there is not a very large difference in the time of rapid arc motion despite significantly differe...

Piezoelectric Arc Movement

Cathode Root Movement

In Figure 8.6, there is not a very large
difference in the time of rapid arc motion
despite significantly different contact
velocities. In this case it is possible that the
delay is caused by the transfer of the arc
from the moving contact to the arc runner,
where factors such as gas flow have a strong
influence. The cathode root on the fixed
contact shows a more gradual movement for
both the piezoelectrically operated and
constant velocity contact systems. The
constant velocity system shows an initial
slowarc rootmovementof approximately 5
ms followed by rapid arc motion at the same
time as the anode.

Reference: Piezoelectrics in Circuit Breakers: Design & Test Paperback – 24 Dec 2014 by Dr Kesorn Pechrach Weaver PhD (Author)

Dr Kesorn Pechrach Weaver: Piezoelectrics in Circuit Breakers: How to use Piezoelectric in Circuit Breakers

Dr Kesorn Pechrach Weaver: Piezoelectrics in Circuit Breakers: How to use Piezoelectric in Circuit Breakers: Piezoelectric in Circuit Breakers It was found that adverse gas flow effects can impede the arc root motion, and that optimization of th...

How to use Piezoelectric in Circuit Breakers

Piezoelectric in Circuit
Breakers

It was found that adverse gas flow effects can impede the arc
root motion, and that optimization of the arc
chamber design could permit the use of
lower contact opening velocities. Recent
investigations [10] have shown that detailed
study of the arc-root phenomena can yield
improvements in arc chamber performance
thus permitting operation at reduced contact
opening velocity.

This now opens the possibility of refinement
of the mechanism using smart materials
actuation. Piezoelectric ceramic actuators
have been used as the trip element in
commercial circuit breakers [5] to provide
low power electronic actuation.

Reference:

Piezoelectrics in Circuit Breakers: Design and Test

Dr Kesorn Pechrach Weaver: Piezoelectrics in Circuit Breakers: How to Achieve Satisfactory Short circuit Performa...

Dr Kesorn Pechrach Weaver: Piezoelectrics in Circuit Breakers: How to Achieve Satisfactory Short circuit Performa...: Achieve Satisfactory Short circuitPerformance   Miniature circuit breakers (MCBs) are widely used for protection from electrica...

How to Achieve Satisfactory Short circuit Performance

Achieve Satisfactory Short circuitPerformance

 

Miniature circuit breakers (MCBs) are
widely used for protection from
electrical faults in domestic and light
industrial installations. These devices
protect against short circuit faults of
typically 1–16 kA. During a short circuit
fault an electric arc is drawn between
opening contacts. The arc is then propelled
by electromagnetic forces into splitter plates
which divide the arc into a number of
smaller arcs. This results in a high arc
voltage, which counteracts the supply
voltage to limit the peak fault current. The
energy released by the fault is reduced and
damage to both the circuit and the circuit
breaker is minimized.

To achieve satisfactory short circuit
performance rapid contact opening and a
high contact velocity are usually necessary.
At low contact opening velocity, the arc root
stays on the contacts for a longer period of
time. Heat is generated in the arc chamber
and the contacts are eroded. This has
resulted in a range of devices where the
opening mechanism is driven by a solenoid
energised by the short circuit current. The
solenoid plunger not only trips the spring
driven opening mechanism, but also directly
drives the opening of the contacts. This
“hammer action” provides a very rapid
acceleration of the moving contact during
the initial contact opening.

In addition to the high current event the
circuit breaker must also trip on moderate
over-current. This is usually achieved with a
bimetallic strip. Increasingly, circuit
protection devices provide additional
functionality such as residual current or arc
fault detection.

Reference: Piezoelectrics in Circuit Breakers: Design & Test Paperback – 24 Dec 2014 by Dr Kesorn Pechrach Weaver PhD (Author)