What is the Difference between circuit breaker and a relay?

Answer 1

A circuit breaker is designed to break a circuit which is carrying current at the time. Where large currents and/or voltages are present, the opening of the circuit may induce dangerous arcing, so means such as air blast must be used to "blow out" the arc. Air breakers are being phased out and replaced with vacuum or SF6 breakers.

An isolator is only designed to isolate a circuit or other component after the current has already ceased, so it doesn't need to have any means to stop the arc.

Thus in high voltage/high current installations such as in power stations or grid switching stations, the initial operation to isolate the circuit, whether planned or as a result of a fault, is by the circuit breaker, the isolator is then used to isolate the circuit breaker for maintenance or repair.

The difference between a circuit breaker and a contactor is that a circuit breaker can break fault current while a contactor cannot. A contactor is typically implemented in series with a fuse which serves to interrupt fault current. An isolator and a contactor are not synonymous.

Answer 2

A relay senses a condition (voltage, flow, amperage, pressure, level, etc.) and allows component actuations (circuit breaker operation, pump start, valve open/close, etc.) to occur. It is part of the control circuitry for a component.

A circuit breaker interrupts electrical current flow by opening a circuit under load conditions.

Both can provide component protection, but only a circuit breaker directly protects components. A relay could actuate a circuit breaker to provide protection.

Answer 3

A circuit breaker is a device for the limiting of current supplied to a circuit. Typically using a bi-metalic strip of metal to sense an increased current. The bi-metallic element will react to the increased current by heating up, and typically 'tripping' a mechanisim that will open or clear the circuit. When the bi-metallic unit cools of, the circuit breaker can usually be reset. After repeated 'trips', it is possible for the circuit breaker to become ineffective, wear out, and require replacement.

A relay is an electro-mechanical device, typically used to control a system or application. Where as a electrical current is passed through a coil of wire, generating a magentic force which then effects a mechanical response. Such as opening or closing a contact that completes another electrical circuit.

A circuit breaker is to designed to protect an electrical circuit, and a relay is designed to control one. Unless a relay has a circuit breaker included in the construction (very uncommon/extremely rare), it is no protection to an electrical circuit.

Answer 4

A circuit breaker is a protective device that interrupts current flow in a fault condition. It is not intended for routine use to turn the load on and off

A contactor is a controlling device that turns the current flow on and off to a load. It is not intended for use as the protective device.

Answer 5

A circuit breaker is a protective device that interrupts current flow in a fault condition. It is not intended for routine use to turn the load on and off
A contactor is a controlling device that turns the current flow on and off to a load. It is not intended for use as the protective device.

A circuit breaker will have a contactor of some type in it. The key here is the circuit breaker is designed to interrupt fault current, while a contactor may be designed to interrupt load current (substantially less). Circuit breakers are much larger than their equivalent contactor / switch, because they are designed to handle the excessive heating that naturally will occur when breaking substatial amounts of current flow.

Answer 6

There is not a huge difference between C.B. and contactor as they work as a switches
but usually CB is normally closed while there a normally open/closed Contactor.
the Contactor used only in a control circuit while CB is used on large power system utility, such as substations. Contactor receive an electrical signal from relay while CB need an auxiliary contactor to trip. Most of the CB needs a arc quenching fluid such as oil, SF6 and vacuum..etc.

Answer 7

1. Relay-"it is the sensing device which is connected to power circuit and if the any parameter of circuit crosses safe limits ,it sends signal to circuit breaker to break circuit."
2. Circuit breaker-" A part of switchgear which is connected in circuit and it opens the circuit on receiving signal from relays"

Answer 8

A circuit breaker is a device designed to protect an electrical circuit from damage caused by excess current flow (overload) or short circuit. A relay is an electrically operated switch that opens and closes circuits electromechanically or electronically. While both devices can control the flow of electricity, a circuit breaker is primarily a protective device, while a relay is used for switching or controlling circuits.