الجهد قواطعالمنخفض

المنخفض الجهد قواطع

القواطع - عن مقدمةالقواطع- أنواع

القاطع- تركيبالقواطع- بيانات قراءة

القواطع- عن مقدمةالقاطع يعرف ووصل Circuit breakerو فصل أداة أنه على

المصدر بين يقع الكهربائية، للدائرةاألحمال (Sourceالكهربائي هذا Loadsوبين من المغذاة

المصدر.( يدويا إما فيه الميكانيكية األجزاء أو ( Manualوتتحرك

التيار ( Electricalكهربائيا) فصل على بدورها لتعملأو محركات سواء كانت مهما األحمال مركز عن الكهربائي

و مراقبة دوا?ئر أو كهربائية لوحات تغذية أو إضاءة دوائر. إلخ ... تحكم

بأشكال ذاتيا أو كهربائيا أو يدويا القاطع تشغيل ويمكنحماية بعناصر مزودا يكون وقد مختلفة، وتوصيالت وطرق

الكهربائية ) تلك ( Fuses Or Relaysالدوائر لحماية الكافيةالتيار إيصال وظيفته فيها،وتكون المستخدم الدائرةإيصاله يراد أنه حالة الكهربائية الدارة إلى الكهربائي

. - فصله يراد أنه حالة في الكهربائي التيار بفضل ويقومالذاتي ) الفصل حالة ( Automaticأما في القاطع به فيقوم

قصر دائرة )) SCحدوث خطأ أو Faultأو الحمل زيادة أومن ذلك غير زيادته أو الجهد هبوط حالة في أو التيار

ال من المختلفة األنواع من يتلقاها (Relays .)إشارات

القواطع- أنواع

المنمنمة الكهربية القواطع( Miniature circuit breaker)

يكون- وحيث النهائية التوزيع دوائر لحمايةلألحمال يكون ما أقرب .القاطع

األحمال - بحماية المنمنة القواطع تقوماالجهادات من الحد وكذلك التوزيع ودوائر

تيار من تنشأ التي والميكانيكية الحراريةالقصر.

علي- المنمنمة القواطع عمل طريقة تعتمدبتحريك يقوم مغناطيسي مشغل وجود

عالية بسرعة القاطع في المتحرك القطبمرحلة في قوسي جهد تولد إلي تؤدي جدا

. القصر تيار قيمة من يحد مما مبكرةمن- الحماية تيار .125الي 0.5يبدأ أمبير

Main CB’s Partes

-Main CircuitPos. 6-5-4

-Operating MechanismPos. 10-11

-Arc ChamberPos. 7

-Protection ReleasePos. 2-9

Definitions

Thermal-Magnetic Principle

Main Current & Arc Current Limiting Path

______________ Main (line) Current Path

---------------- Arc Current Limiting Path

Thermal Principle (Overload Protection)

• The thermal part of the circuit breaker utilizes a bimetallic strip electrically in series with the circuit. The heat generated by the current during an overload deforms the bimetallic strip and trips the circuit breaker.

Example:Overload occurs when the vacuum is obstructed and the power cord gets overheated.

NOTE: The thermal part of the circuit breaker is temperature sensitive and can be adversely affected by changes in ambient temperature (MCB calibrated at 40° C (104° F) ).

Magnetic Principle(Short Circuit Protection)

• The magnetic part of the circuit breaker consists of an electromagnetic coil and an armature device that opens the movable contact quickly to protect the circuit whenever the current (short circuit current) exceeds a predetermined value. This happens because the current in the coil generates sufficient magnetic flux to attract the armature. Reset is manual and rapid.

Example:Short circuit occurs when the hot wire and neutral/ground accidentally come together.

Trip-Characteristics & Applications

Section AOverload

Section BShort Circuit

Current

Tim

eZ Y

W

VX

U

Trip-Characteristics & Applications

• This section reflects the protection behavior of the circuit breaker when an overload occurs. Usually the overload increases its value above the rated current slowly.

–The left line shows when the MCB does not trip.–The right line is the opposite, the MCB must trip!–The middle black line indicates the “ideal” trip curve. Due to manufacturing tolerances

and surrounding influences, the MCB can only be calibrated “around” this line.

Z YSection AOverload

Section A- OverloadCurrent

Tim

e

Trip-Characteristics & Applications

• This section reflects the protection behavior of the circuit breaker in the case of an inrush current or a short circuit.

–Inrush current occurs when the load is turned on and off (the inrush of a regular motor is approximately 6x the rated current). It is VERY important to know the inrush current when selecting the proper circuit breaker. The time of an inrush is usually between 100-500ms. If the correct circuit breaker is selected it will be insensitive to the inrush current (see points “X” & “W”). The circuit breaker will trip if the current exceeds 16XRC in 100ms (see point “V”).

Section BShort

CircuitW

VX

U

Section B - Short CircuitCurrentTi

me

Section B - Short Circuit - Continued

–Short Circuit Current is the current which occurs in the case of a hot wire and ground/neutral coming together.

Section BShort

CircuitW

VX

U

Current

Tim

e

This current is usually very high (between 300A - 2000A) and the circuit breaker will trip within milliseconds.

Note: If the MCB has a rated current of 10A, it will trip in 7ms, if the short circuit current is 400A (see point “U”).

The B-Trip Characteristic

• Applications–Business equipment, wiring protection, lighting, appliances,

control circuits, some motors and some electronic circuits• Available current

–0.3A-60/63A

CURRENT

TIM

E

The C-Trip Characteristic

• Applications–Low inrush, 3-4x rated current, motors, lighting, wiring

protection, appliances, business equipment, control circuits• Available current

–0.3A-60/63A

The D-Trip Characteristic

• Applications–High inrush, 10-16x rated current, motors, transformers,

power supplies, heaters, reactive loads• Available current

–0.3A-60/63A

The E-Trip Characteristic

• Application–High efficiency motors, which have very high inrush, 12x

rated current• Available current

–0.3-60/63A

The G-Trip Characteristic

• Applications–General industrial, including motors, some transformers,

solenoids, control circuits, lighting, wiring• Available current

–0.3-60/63A

The Z-Trip Characteristic

• Applications–Semiconductors, components with low surge current

and short circuit withstand capabilities• Available current

–0.3-50A

Summary of Applications/Trip Curve Selection Guide

Summary of Applications/Trip Curve Selection Guide(Continued)

.

Style

• (1 pole, B-Trip characteristic, UL Type, 16 A).

MA Three Phase Adjustable Trip Miniature Circuit Breaker

UL508 listed

CAN/CSA-C22.2 No. 14 certifiedC

MA Three Phase Adjustable TripMiniature Circuit Breaker

• General Specifications–Complies with various national and international standards

e.g. UL, CSA, VDE, IEC, CE–DIN Rail mountable–Adjustable thermal trip allows finalization of initial designs before

procurement of the load equipment is complete–Voltage rating: 480Y/277 V AC–Rated current from 0.16A - 40A–3 poles

• Accessories available (same as V-EA MCB)–Auxiliary Switch–Shunt Trip–Undervoltage Trip

The MA was designed to handle the high inrush loads of 3 phase transformers, power supplies, motors, etc.

Circuit Breaker Accessories

Accessories can be factory or field mounted on V-EA miniature circuit breakers and MA motor protection switches for enhanced control and monitoring capabilities. Field mounting kits include all necessary parts and instructions. Accessories can be gang mounted on a single breaker (the Auxiliary Switch in the outside position). The mounting arrangement links the internal latch-pins for the tripping mechanisms, ensuring simultaneous trips. Handles are linked to simplify manual resetting.

Remote Trip-Shunt Trip

• Coil actuated, the FA Shunt Trip allows electrical remote tripping of a breaker. It is trip-free and the housing and terminal specifications are the same as for V-EA miniature circuit breakers.

• The Shunt Trip contains its own contacts which break the tripping power circuit when tripped. It is available with trip-coils in the most standard control voltages.

Undervoltage Trip

• Reset-Hold Voltage = 0.85 x Ve• Drop-Out Voltage = 0.35 to 0.7 x Ve

Re-power your system under controlled conditions following a power loss or serious undervoltage. Altech UA Undervoltage Trips are coupled to the tripping latch pins of the V-EA or MA to which they are attached, reliably producing trips at the drop-out voltage and preventing resetting when less than 85% line voltage is present. The Undervoltage Trip is provided with at least 6-inch pigtails of stranded fixture wire for hook-up to the V-EA or MA line terminals.

Auxiliary Switch

• Altech H Auxiliary Switch is suitable for logic interrogation and for use as a two-circuit Form C contact. It can also function as an auxiliary switch for control circuits.

More Accessories

القواطع- أنواع

المقولبة ا?لكهربية القواطع( Moulded case circuit breaker)

من- أساسا القواطع هذة تتكونصندوق داخل مغلقة متكاملة وحدة

وأغلب عازلة مادة من مصنوع محكميمكن ال بحيث غيرقابلة القواطع هذة

بأكملة القاطع استبدال أو صيانتها. عطل بأي إصايتة حالة في

من- الحماية تيار 3200الي 100يبدأأمبير.

القواطع- أنواع

الهوائية الكهربية القواطع( Air circuit breaker)

الهوائية- الكهربية القواطع تستخدمالعالية المقننة للتيارات عادة

إما الكهربية الشبكة في وتستخدمعمومية كقواطع أو عمومي كقاطع

للفرعيات.من- عالية سعات ذات القواطع هذة

. التيار حيث

القواطع- أنواع

المقولبة الكهربية القواطع أجزاء( Moulded case circuit breaker).

Residual Current Circuit Breakers (RCCB)Residual Current Circuit Breakers (RCCB) األرضي التسريب األرضي قاطع التسريب قاطع

Fault Current Circuit

Residual Current Circuit

القواطع- أنواع

الكهربية القواطع معايرة

العيار الحراري

العيار المغناطي

سي

القواطع- أنواع

القواطع بيانات قراءة كيفيةطرازالق

اطع

الجهد المقننأقصي

تيار للقصر

CONVENTIONAL CIRCUIT BREAKERS

1- Automatic SwitchThe simplest circuit interruption device is the knife switch shown in Fig. By closingthe switch against the action of a spring, energy is stored. By applying a small force on thelatch, the stored energy is released and the contacts open within a short time.

2-Air-Break Circuit BreakersAir-circuit breakers cool the gases to naturally deionize them, causing arc interruption. The arc can be stretched. Its resistance can be increased by increasing its length. The increase in resistance is significant so that the current and voltage are brought into phase.If the phase difference between the system voltage and the short-circuit current is reduced, when the current is interrupted at its zero value, the recovery voltage is very low at that instant.The application of high-resistance interruption is limited to low- and medium-power ac circuit breakers. It is also used for low- and medium-power dc circuit breakers.

METHODS FOR INCREASING ARC RESISTANCEThe following methods increase the arc resistance:1. Arc lengthening. The resistance is approximately

proportional to the arc length.2. Arc cooling. A decrease in temperature increases the

voltage required to maintain ionization.Therefore, cooling effectively increases the resistance.

PLAIN BREAK TYPE

The plain break type is the simplest type of air-break circuit breaker. The contacts are made in the shape of two horns, as illustrated in Fig. 19.4. The arc initially strikes across theshortest distance between the horns. Then it is driven steadily upward by the convection currents which are caused by heating the air during arcing. The arc extends between the horns. This results in lengthening and cooling of the arc.The arc interruption process is relatively slow. It limits the application of these circuit breakers to 500 V and low-power circuits.

MAGNETIC BLOWOUT TYPEThis type of circuit breaker extinguish the arc by means of a magnetic blast. It is limited to circuits up to 11 kV. The arc is subjected to the action of a magnetic field set up by coils connected in series with the circuit being interrupted (Fig.). These coils are called blowout coils because they help blow out the arc magnetically. The arc is magnetically blown into arc chutes where the arc is lengthened, cooled, and extinguished.The breaking action becomes more effective with heavy currents. This results in higher breaking capacities for these breakers.The arc chute is an efficient device for quenching the arc in air. It performs the following

interrelated functions:1. It confines the arc within a restricted space.2. It provides control of the movement of the arc to ensure extinction occurs within the device.3. It cools the arc gases to ensure extinction by deionization.

ARC SPLITTER TYPEThe blowouts in these breakers consist of steel inserts in the arcing chutes. These inserts are arranged so that the magnetic field induced in them by the current in the arc helps move the arc upward. The steel plates divide the arc into a number of short arcs in series.Figure illustrates an air-break arc splitter-type circuit breaker.APPLICATIONIn general, air-break circuit breakers are suitable for the control of power station auxiliaries and industrial plants. They combine a high degree of safety with minimum maintenance.They do not require any associated equipment such as compressors. Since they have no oil, they are recommended for locations where fire or explosion hazards are feared.

OIL CIRCUIT BREAKERSIn oil circuit breakers, the arc energy is used to crack the oil molecules to generate hydrogen gas. The hydrogen is used to sweep, cool, and compress the arc plasma. This deionizes the arc plasma in a self-extinguishing process.Even if the breaker contacts are immersed in oil, arcing still occur during contact separation.The heat from the arc evaporates the surrounding oil and dissociates it into carbon and a substantial volume of gaseous hydrogen at high pressure. The heat conductivity of hydrogen is high, resulting in cooling of the arc and the contacts. This increases the ignition voltage and extinguishes the arc.

The cooling caused by the hydrogen (due to its high conductivity) is very effective. It increases the voltage required for reignition significantly (5 to 10 times higher than the reignition voltage required for air).Hydrogen is produced spontaneously in arcs under oil.Interruption of heavy short-circuit currents generates extremely high pressures which should be released safely or controlled properly. These high pressures are used to extinguish the arc which generated them.

Advantages of OilAs an arc extinguishing medium, oil has the following advantages:1. Oil produces hydrogen during arcing. The hydrogen helps extinguish

the arc.2. The oil provides insulation for the live exposed contacts from the

earthed portions of the container.3. Oil provides insulation between the contacts after the arc has been

extinguished.Disadvantages of Oil Circuit BreakersOil has the following disadvantages when used as an arc extinguishing medium:

1. Oil is inflammable and may cause fire hazards. When a defective circuit breaker fails under pressure, it may cause an explosion.

2. The hydrogen generated during arcing, when combined with air, may form an explosive mixture.

3. During arcing, oil decomposes and becomes polluted by carbon particles which reduces its dielectric strength. Hence, it requires periodic maintenance and replacement.