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)

Dr Kesorn Pechrach Weaver: Piezoelectrics in Circuit Breakers: Contact speed setup

Dr Kesorn Pechrach Weaver: Piezoelectrics in Circuit Breakers: Contact speed setup: 5.1 Contact speed setup The opening contact mechanism was modified to reduce contact speed from 10 m/s down to 1 m/s. There are tw...

Contact speed setup

5.1 Contact speed setup

The opening contact mechanism was modified to reduce contact speed from 10 m/s down to 1 m/s. There are two important parts in this system. The first part is the instrument to measure the speed of contact and the second part is the instrument to control the speed. The instrumentation used to measure the contact velocity is the displacement sensor which is connected to the solenoid. The method used to control the contact velocity is to control the supply voltage to the motor of the solenoid.

5.1.1 Displacement sensors

The pivot mechanism moves in a curve with a very high speed, it is very difficult to measure speed directly from this system. It is not very difficult to measure the velocity of the solenoid movement and calculate the speed of the pivot mechanism and contact. The displacement transducer uses a filter pattern together with intensity sensitive photo sensors. Details of the displacement transducer control circuit and differential op-amp circuits are shown in Figure 5.1 –5.2. 

Figure 5.1:  Control diagram of displacement transducer

Figure 5.2: Detail of the differential circuit for output signal of displacement transducer

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

Dr Kesorn Pechrach Weaver: Piezoelectrics in Circuit Breakers: Piezoelectric Instrumentation: Piezoelectric Instrumentation The Piezo-ceramic used as the actuator in this paper is Lead Zirconate Titanate (PZT). The...