Switchgear Protection

Although thermal magnetic switches are used as a circuit breaker, they are used in circuit opening and closing operations for normal circuit breakers. While the thermal magnetic switch is responsible for opening and closing the circuit while the normal circuit is in use, in unexpected situations (such as a short circuit), the switch turns into a protection switch that breaks the circuit thanks to its limiter feature. The main mechanism that performs all these operations is known as compact switch. Compact switches used in buildings and commercial areas as well as industrial areas generally operate in electrical panels thanks to the protection mechanism. MCCB is known as the abbreviation of thermal magnetic, compact switch in the industrial field.​

Thermal magnetic switches generally provide protection at a current value in the range of 10 to 1600 amperes. In particular, they show the feature of protecting the system against overloading. As the degree of interruption, a value between 10 kA and 200 kA is foreseen in the devices. It is suitable for use in commercial or industrial areas that usually require heavy loads. If the rated current is higher than 100 A, the use of compact switches is recommended.

Especially in the industrial field, the question of what a thermal magnetic (compact) switch is and why it is used is frequently asked. Compact switches are used to protect from overloading, as they directly operate the protective limiter mechanism in overload situations. Thanks to its magnetic protection properties, it is used as a circuit breaker between control centers, telephone exchanges, electrical panels and networks. In case of overload detection, the switches are activated and used as circuit breakers thanks to their switching features. For this reason, the use of thermal magnetic switches is high, especially in industrial areas, due to the fact that overloading is more common. It is frequently preferred in buildings or industrial areas due to its complete protection and circuit breaker mechanism.

One of the most important parts of compact switches that provide protection in magnetic fields are the contact parts that show protection. In general, different types of contacts made of silver, wolfram or graphite alloys are used in industrial areas. Generally, wolfram alloy is preferred for hard contacts, while silver or graphite alloy is preferred for soft areas. The thermal magnetic switch is of great importance in many areas, as it provides protection against overcurrent in all kinds of areas. Therefore, it is necessary to pay attention to the brand and quality in the selection of thermal magnetic switches. Switches that do not adapt to the area used for protection will also lose their properties. In particular, the use of switches that meet the necessary standards in terms of safety is also of great importance in case of a possible voltage. Along with all these features, thermal magnetic switches consist of different isolation systems to create the necessary safety net.

Selection Criteria

Thermal protection feature is a very important issue in thermal magnetic switches. It is one of the safety measures that the thermal protection switch activates in case of overload detection. In particular, when fault current occurs, thermal protection activates and protects the system. The thermal protection feature is generally provided over the bimetal, which occurs due to the temperature change as a result of the increase in current. Bimetal experiences bending due to high current and temperature. Overload as a result of bending is also seen above the nominal values. Values ​​on bimetals increase gradually due to the increase in current, increase in temperature and formation of high voltage. In general, bimetals bend and their temperature increases. Along with this whole process, when the bimetals reach a certain temperature value, the circuit breakers are activated. After the bimetals sense the excessive current, the breakers are disabled thanks to its direct protection feature. Disabled breakers also allow the switches to cut off the electricity. This protection mechanism, which is generally of great importance in the industrial field, is also a precaution against accidents caused by excessive current. Along with all this, the electricity is cut off via the switch and the protection feature is activated directly. This process is known as thermal protection in industrial and commercial areas. For the thermal protection to work correctly, the contacts must also be in working condition.

Magnetic Protection Feature

Magnetic protection, on the other hand, is provided by a mechanical mechanism that works with the magnetization created by the magnetic field created by the current in MCCBs against excessive currents. Currents such as short circuit, phase-phase fault, phase-earth fault can cause serious damage to the equipment, pose a high risk to human life and must be interrupted as soon as possible, therefore magnetic protection, which is a sudden protection, is needed. The magnetic protection mechanism is calibrated to trip with large fault currents, but should not respond to currents below.

  • Normal operating current
  • Short-term and low-magnitude overcurrent conditions that normally occur in some electrical equipment


Saypro Elektrik

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