When a facility has high energy needs, safety becomes an utmost concern. An air circuit breaker (ACB) effectively protects facilities and employees from increased electricity flow. ACBs also ensure that electrical systems are running efficiently and correctly.
Below, we’ll cover the basics of ACBs and how they work. We’ll also look at some of the different types of ACBs and their applications.
How Does Air Circuit Breaker (ACB) Work?
Circuit breakers are designed to stop the flow of electricity under certain conditions, usually during situations like an overcurrent or short circuit or to direct the flow of the system. A circuit breaker is made up of contacts that will separate when a problem occurs. Stopping the flow of electricity keeps conditions safe and prevents damage to equipment.
Air circuit breakers operate using pressurized air. As the breaker trips, the contacts will separate, creating an arc. ACBs eliminate the arc, keeping the current steady and safe. ACBs are an alternative to oil circuit breakers, which are not as safe. It’s also important not to confuse ACBs with vacuum circuit breakers, which extinguish the arc using a vacuum. A VCB is the better choice for indoor, high-voltage use, while an ACB is better for industrial settings.
In an ACB, when the contacts separate – due to overcurrent, short circuit or for operating purposes – the ACB works to eliminate the arc, making the equipment safer. The ACB uses a combination of air pressure and conductive elements to guide the arc away from the circuit safely and then stretches it until it is eliminated.
What are the Main Components of ACB?
Several components work together in an ACB. One of the main features is a blast valve. When the arcing contacts separate and the arc forms, the blast valve opens arc chutes. Pressurized air pushes through the arc, disconnecting it from the contacts.
The pressurized air pushes the arc towards arcing probes and rings. These are conductive elements that help to move the arc away from the contacts. As the arcing contacts get farther apart, the arcing probes and coils get closer together, allowing them to attract the arc.
The arc is moved into the chutes toward an arcing electrode. Eventually, the arc is pushed through the chutes and stretched until it is completely eliminated.
Types of ACB
There are four main types of ACBs. Below, we’ll discuss each type, its functions and its use cases.
Plain Brake Type ACB
Plain brake-type ACBs are the most basic design. The arc contacts are shaped like horns. When the circuit breaks and the contacts move apart, the arc forms between them. The plain brake type then uses air pressure to elongate the arc until it extinguishes.
These are often used in low-voltage situations with up to 12,000 volts. Plain brake types ACBs work with DC and AC currents.
Magnetic Blowout Type ACB
A magnetic blowout type ACB uses a magnetic field to aid in eliminating the arc. The magnetic field does not extinguish the arc. When the arc is formed, blowout coils create a magnetic field. The magnetic field helps to move the arc along the chutes, where the pressurized air elongates it and eventually eliminates it.
Magnetic blowout-type ACBs are used in equipment with voltages below 11,000 volts.
Air Chute ACB
Air chute ACBs employ two types of contacts – primary contacts made of copper and arcing contacts made of silver. During a break, the primary contacts separate before the arcing contacts, protecting the primary contacts from the arc. The arc contacts also close before the primary contacts for protection.
Air chute ACBs are used in high-voltage situations, with voltages reaching 420 KV or more.
Air Blast Circuit Breaker
An air blast circuit breaker uses pressurized air to move and extinguish the arc. When the break creates the arc, a valve opens, allowing pressurized air to move up through an arc chute. The air guides the arc up where it elongates and is extinguished.
Air blast circuit breakers are used in medium-to-high voltage situations, with voltages of up to 15 KV.
Applications of Air Circuit Breakers
If you have heavy equipment with high energy needs, an ACB is a worthwhile investment. Most equipment is costly to repair or replace, so an ACB can prevent many issues that may arise. ACBs protect your equipment in the event of energy malfunction.
It’s important to test an ACB to ensure it works properly regularly. The testing procedure involves first checking the ACB inside and out to make sure that all equipment is in good order. You may need to clean or lubricate some areas.
Next, you’ll perform mechanical and electrical operation tests to ensure proper functioning. You’ll perform injections on electronic trip components. This process will calibrate the breaker to certain points.
If you’re not comfortable working with electric equipment, you can always hire a professional to test the ACB. They can safely and effectively check that your ACB is working.
How to protect your grid assets by creating circuit breakers that rapidly detect faults, reliably communicate via wired and wireless interfaces and efficiently generate power from the line.
As shown in the figure below, the system consists of 17 structures, namely AC/DC power supply (voltage input)、DC/DC power supply、AC/DC power supply (current input)、Signal input protection、Protection analog front end、Leakage current analog front end、Measurement analog front end、Display (HMI)、Digital processing、Self-diagnostics/monitoring、Signal isolation、Local debug、Serial interface、HMI、Power stage、Trip settings、Signal output protection
AC/DC power supply (voltage input)
DC voltage is derived from 230V/110V AC lines to power the breaker. Isolated AC/DC converter is used to derive necessary power supply from the AC lines. AC/DC power supply (voltage input) includes Linear & low-dropout (LDO) regulators、Isolated DC/DC converters & modules、Transformer drivers, the Corresponding products are TLV709、TPS55010、SN6501
DC/DC power supply
An auxilary DC voltage source can be used to power up the system even during fault conditions in the absence of power from CT. DC/DC power supply includes Buck converters (integrated switch), the Corresponding products are LMR54406、TPS62177
AC/DC power supply (current input)
DC voltage required for the ACB can be self powered by deriving power from Current Transformer. Output voltage from CT is regulated using switch based shunt regulators. AC/DC power supply (current input) includes Shunt voltage references、N-channel MOSFETs、Series voltage referencesP-channel MOSFETs、Series voltage references、P-channel MOSFETs、Comparators, the Corresponding products are TLVH431B、CSD17577Q3A、REF1925、CSD23280F3、LM2903B
Display (HMI)
The interaction between ACB and the user is provided by Display (HMI) system enabling easy configurations and status display. Display (HMI) includes Backlight LED drivers、RGB LED drivers、MSP430 microcontrollers、Oscillators、D-type latches、Light sensors, the Corresponding products are TPS61165、TLC59283、MSP430FR5738、LMK6C、SN74LVC1G373、OPT101
Signal input protection
Air Circuit Breakers interface with Current Transformers, Potential Transformers and Shunts for measuring currents and voltages. The signal path is subject to electromagnetic disturbances (EMC) that can either damage sensitive electronic or create false measurements. An effective input protection scheme is necessary to comply with standards like the IEC61000. TVS diodes and common mode chokes can help clamp and reduce harmful interference. Signal input protection includes ESD protection diodes、TVS diodes, the Corresponding products are ESDS552、TVS1400
AC/DC power supply (current input)
DC voltage required for the ACB can be self powered by deriving power from Current Transformer. Output voltage from CT is regulated using switch based shunt regulators. AC/DC power supply (current input) includes Shunt voltage references、N-channel MOSFETs、Series voltage references、P-channel MOSFETs、Comparators, the Corresponding products are TLVH431B、CSD18514Q5A、REF1930、CSD23280F3、TLV7011
Protection analog front end
Protection Analog Front End provides signal conditioning and flexible gain amplification to detect fault/overload conditions in the lines. With line currents going very high, protection AFE has to provide high measurement accuracy over wide range of input. Protection analog front end includes Precision op amps (Vos<1mV)、General-purpose op amps、Analog current-sense amplifiers、Audio op amps、Programmable & variable gain amplifiers (PGAs & VGAs)、Instrumentation amplifiers、Precision ADCs、Analog switches & muxes、Series voltage references, the Corresponding products are TLV333、TLV9004、INA240、OPA1632、PGA117、INA317、ADS131E08、TPS3702、REF35
Leakage current analog front end
Leakage current analog front end is used for monitoring leakages between line and neutral. If the leakage is above the thresholds defined in standards/trip settings then tripping action is initiated. Leakage current analog front end includes Precision op amps (Vos<1mV)、General-purpose op amps、Analog current-sense amplifiers、Audio op amps、Programmable & variable gain amplifiers (PGAs & VGAs)、Instrumentation amplifiers、Series voltage references, the Corresponding products are TLV333、TLV9004、INA216、OPA1612、PGA117、INA317、SN74CBTLV3251、REF1930
Measurement analog front end
Measurement Analog Front End provides signal conditioning of three phase voltage and current signals obtained from the sensors in order to perform accurate calculations of three phase parameters such as RMS, active power and reactive power. Voltage zero cross over is detected for accurate measurement of frequency. Measurement analog front end includes Precision ADCs、Comparators、General-purpose op amps、Precision op amps (Vos<1mV)、Analog current-sense amplifiers、Audio op amps、Programmable & variable gain amplifiers (PGAs & VGAs)、Instrumentation amplifiers、Analog switches & muxes、Series voltage references, the Corresponding products are ADC101C021、LM393B、TLV9052、TLV333、INA216、OPA1604、PGA117、INA188、TS3A24157、REF1930
DC/DC power supply
An auxilary DC voltage source can be used to power up the system even during fault conditions in the absence of power from CT. DC/DC power supply includes Buck converters (integrated switch), the Corresponding products are LMR54406、TPS563203
Display (HMI)
The interaction between ACB and the user is provided by Display (HMI) system enabling easy configurations and status display. Display (HMI) includes Backlight LED drivers、RGB LED drivers、MSP430 microcontrollers、Oscillators、D-type latches、Light sensors, the Corresponding products are TPS61165、TLC59283、MSP430F5529、LMK61E2、SN74LVC1G373、OPT3002
Digital processing
Advanced algorithms for processing and detecting arcs and ground faults are implemented using a microcontroller. Multiple peripheral such as ADCs, Timers, GPIOs and communications dictate the MCU requirements. Digital processing includes MSP430 microcontrollers、Wi-Fi products, the Corresponding products are MSP430FR5738、WL1837MOD
Self-diagnostics/monitoring
A supervisor IC is used to monitor the power supply levels. It provides a fixed delay during a power glitch or when the reset function is forced on the MCU. Self-diagnostics/monitoring includes Supervisor & reset ICs、Analog temperature sensors、Digital temperature sensors, the Corresponding products are TPS3840、TMP235
Signal isolation
Signal isolation provides isolation between MCU and the serial interface. Signal isolation includes Digital isolators、Isolated RS-485 transceivers、Isolated CAN transceivers, the Corresponding products are ISO7720、ISO1176、ISO1050
Local debug
Local Debug is required for performing routine maintenance or trip tests for each protection function. Interface such as RS-232 or USB can be used for this purpose. Local debug includes RS-232 transceivers、USB hubs & controllers, the Corresponding products are TRS3243E、TUSB321
Serial interface
Wire interface consists of variety of options depending on the use cases which consists of RS485, CAN, ethernet etc. Serial interface includes RS-485 & RS-422 transceivers, the Corresponding products are THVD1500、SN65176B
HMI
LEDs are used for status indication. HMI includes RGB LED drivers、D-type latches, the Corresponding products are TLC59283、SN74LVC1G373
Power stage
The potential free digital outputs are used for status indication and control of external trip devices such as contactors. Power stage includes Solenoid drivers, the Corresponding products are DRV110
Trip settings
Trip settings provides flexibility to program multiple parameters for protection. Parameters related to current settings, trip time settings can be programmed and stored. Trip settings includes Noninverting buffers & drivers, the Corresponding products are SN74LVC1G126、SN74LVC1G07
Signal output protection
Air Circuit Breakers interface with the external interfaces for communicating data and user interface. The signal path is subject to electromagnetic disturbances (EMC) that can either damage sensitive electronic or create false data. Signal output protection includes ESD protection diodes、TVS diodes, the Corresponding products are TPD1E05U06、TVS1400
Conclusion
An ACB is a wise choice when it comes to protecting your equipment and facility, along with keeping all of your electrical needs running smoothly. ACBs are safer and easier to maintain than oil circuit breakers.
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