1.
ELCB (Earth Leakage Circuit Breaker)
Construction:
An ELCB consists of a toroidal core through which live and neutral conductors pass. The
primary winding is connected to the live conductor, and the secondary winding is connected to
the earth. The core detects leakage current, and a relay mechanism trips the circuit if leakage
exceeds a safe limit. The device has moving and fixed contacts that open during faults. It is
housed in an insulated casing, with a test button to check functionality.
Working Principle:
The ELCB detects leakage current by comparing the current in live and neutral conductors. If
there is a difference due to leakage, the relay activates and trips the contacts, disconnecting the
circuit to prevent electric shocks and fires.
Applications:
Prevent electric shocks: Used in homes and industries to protect against electric shocks from
earth leakage.
Protection for sensitive equipment: Protects equipment from damage caused by earth faults.
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2. RCCB (Residual Current Circuit Breaker)
Construction:
The RCCB features a toroidal core with both live and neutral conductors passing through it. The
core detects any residual current imbalance between live and neutral. A trip mechanism
activates when this imbalance occurs, causing the moving contacts to disconnect the circuit.
The entire unit is housed in a molded insulating body for protection, and it includes a test button.
Working Principle:
The RCCB detects residual current by comparing live and neutral current. If there’s an
imbalance (leakage), it triggers the trip mechanism to open the contacts and disconnect the
circuit, preventing shocks and electrical fires.
Applications:
Protection against electric shocks: Commonly used in homes and commercial buildings to
prevent electric shocks.
Prevention of electrical fires: Used to reduce the risk of fires caused by leakage currents.
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3. MCCB (Molded Case Circuit Breaker)
Construction:
The MCCB is housed in a molded plastic case and contains a thermal trip unit (bimetallic strip)
and a magnetic trip unit. The thermal trip handles overloads, while the magnetic trip responds to
short circuits. The breaker has moving and fixed contacts that open during faults. Arc quenching
chambers suppress electrical arcs during disconnection. The device is protected by an insulated
case.
Working Principle:
The MCCB operates by detecting overloads with the thermal trip unit. When the current exceeds
the preset value over time, the bimetallic strip bends and trips the breaker. The magnetic trip
unit quickly disconnects the circuit during short circuits by using electromagnetic forces to open
the contacts.
Applications:
Overload and short-circuit protection: Common in industrial and commercial circuits for motor,
transformer, and lighting protection.
High-capacity circuits: Suitable for applications with high power demands.
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4. MPCB (Motor Protection Circuit Breaker)
Construction:
The MPCB is housed in a molded plastic casing and contains a thermal trip unit (bimetallic strip)
for overload protection and a magnetic trip unit for short circuit protection. It has adjustable
settings for motor overload and inrush current. The device also includes phase failure protection
to prevent damage during phase loss. It has moving and fixed contacts to disconnect the motor
when necessary, and a test button for checking functionality.
Working Principle:
The MPCB protects motors by sensing overloads with the thermal trip unit (bimetallic strip),
which trips the circuit when excessive current is detected. The magnetic trip unit responds to
short circuits and disconnects the motor quickly, preventing damage.
Applications:
Motor protection: Specifically designed to protect electric motors from overloads, short circuits,
and phase loss in industrial settings.
Industrial machinery: Widely used in applications like pumps, compressors, and conveyor
systems.
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