Thermal-Magnetic Circuit Breakers

Operation Principle

Normal Load Operation

Thermal (Inverse Time) Trip Mechanism.

The thermal trip mechanism operates in response to overload conditions. The mechanism includes a bimetal element located behind the trip bar. The bimetal element is part of the current-carrying path. When there is an overload, the increased current flow heats the bimetal and causes it to bend. As the bimetal bends, it touches and rotates the trip bar causing the circuit breaker to trip. The time needed for the bimetal to bend and trip the circuit breaker varies inversely with the current.

Short Circuit Operation

Magnetic (Instantaneous) Trip Mechanism.

The magnetic trip mechanism operates when there is a high current (short circuit) in the current path. The mechanism includes an electromagnet and an armature. When high-level current passes through the conductor, the magnetic field strength of the electromagnet rapidly increases and attracts the armature. As the top of the armature is drawn to the electromagnet, the armature rotates the trip bar causing the circuit breaker to trip.

Features:

  • The Fuchs-type thermal-magnetic circuit breakers are ideal for upstream cascading breaker systems.
  • Thermal-magnetic breakers can be mounted in any position. The tripping characteristic does not change.
  • Magnetic only tripping circuit breakers are available, ideally suitable for motor short circuit protection.
  • Specially designed breakers for class 2 coordination with contactors and overload relays.

Triple Pole Circuit Breakers (Mixed Load)

TypePolesTerminalskA@No. of Interphase BarriersRating (A)
415 V525 V
G15D3G11515216, 20, 32, 40, 50, 63
G1151580, 100
G11515125
F15D3G115154150, 160
G11515175, 200, 225
G4B1515250
G25D3G12518216, 20, 32, 40, 50, 63
G1251880, 100
G12518125
F25D3G125224150, 160
G12522175, 200, 225
G4B2522250
G35D3G13522216, 20, 32, 40, 50, 63
G1352280, 100
F35D3G135224125
G13530150, 160
G13530175, 200, 225
G4B3530250
F65DV3G16535420-25, 32-40, 45-63
G1653570-100
G1653590-125
G16535125-160
G4B6535175-250

KD Circuit Breakers (Mixed Load)

TypePolesTerminalk@No. of Interphase BarriersRating (A)
415 V500 V525 V
K25D3G4B2522-4250
3G4B2522-4300, 350, 400
K35D3G4B3530304250
3G4B3530304300, 350, 400
3G4B3622-4500, 630
K50D3G4B5040354500, 630

KDE Electronic Circuit Breakers (Adjustable)

TypePolesTerminalk@No. of Interphase BarriersRating (A)
415 V500 V525 V
K35DE3G4B3530304200-400
K50DE3G4B5040354300-630
K65DE3G4B6550504200-400
K70DE3G4B7050-4300-630

Triple Pole Circuit Breakers (Mixed Load) Electronic Adjustable

TypePolesTerminalskA@No. of Interphase BarriersRating (A)
415 V500 V
N83DE3G4B85++65++2500-1000
32600-1250
32800-1600

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