From home electrical systems to
advanced industrial circuits, circuit breakers protect power systems from
electrical power overloads, ground faults, arc faults and other scenarios where electricity
could pose a safety risk to people and property. What types of circuit breakers exist
and why? Let's take a quick look. The most common type of circuit breaker consists
of an electromagnet and a movable armature with an electrical contactor at the end. The arm
is connected to a spring or other a
ctuator. The arm contactor makes contact with a
stationary contactor inside the breaker, completing the circuit and allowing
electricity to flow. When a problem occurs, the actuator forces the contactors
apart, stopping the flow of electricity. Let's review the types of circuit breakers. MCBs are commonly used in low voltage applications
such as 24 volt DC or 125 volt AC circuits. MCCBs are the most common type of circuit breaker. They have higher current-carrying
capacity than miniature br
eakers. ICCBs are similar to molded case
circuit breakers, but unlike MCCBs, insulated case breakers often use an electronic
circuit to monitor electrical current. ACBs are the first breakers on our list to move exclusively beyond low voltage to
medium-voltage power distribution. A VCB has a vacuum interrupter, sometimes called a
vacuum bottle, and a spring-loaded moving contact. Gas circuit breakers typically use
a dielectric insulating gas such as sulfur hexafluoride to help cool
down an
d quickly extinguish an arc. A circuit breaker has multiple connection types. Plug-in circuit breakers connect to the bus
bar using plugs on either side of the breaker. Bolt-On breakers connect to the
bus bar using threaded studs. Feed-Through circuit breakers have lugs on both sides that allow cables to
be connected to the breaker. Next let's review Poles. The number of poles determines
how many completely separate circuits can be simultaneously
protected by a circuit breaker. Typically us
ed in fans, lighting equipment
and single-phase applications. This is the most common configuration found in households. Used when connecting to multiple phases of a
single or 3 phase circuit. This configuration is commonly used in homes for 240 volt
circuits, such as dryers and air conditioners. Used in 3-phase applications. This is
commonly used to feed 3-phase subpanels or 3-phase-rated equipment such as large motors. Used in 3-phase systems with an
extra fourth pole to protect the neutr
al circuit within the system. This is
commonly used in data centers and scenarios requiring a high degree of coordination
or protection of sensitive equipment. Let's define some important terms
related to circuit breakers. Voltage is electricity at
rest and is measured in volts, while current is an electrical charge in
motion over time and is measured in amps. The difference between the high point and
low point in an electrical field defines the potential or voltage present.
In alternatin
g current systems, the voltage changes from negative to positive
and back to positive in a continuous wave. Direct current systems maintain a consistent
voltage, either positive or negative. Amperes are the units used to measure current or
an electrical charge in motion. When describing voltage, current and resistance, a common
analogy is a water tank. In this analogy, charge is represented by the water amount, voltage is represented by the water pressure
and current is represented by the w
ater flow. Ampere interrupting capacity
is the maximum current that a circuit breaker has been designed to interrupt, protecting downstream equipment and people. AIC
is measured in amps at a particular voltage. Various circuit breaker accessories come into play to enable features such as remote
indication and automatic operation. A few examples: The auxiliary switch indicates the
breakers present condition: open or closed. A bell alarm provides remote indication that a circuit breaker has tr
ipped
due to an electrical fault. A motor electric operator helps
compress a spring so it can open. A shunt trip remotely trips a
breaker when voltage is applied.
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