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BT139B-800,118 Application Field and Working Principle

Thyristors and TRIACs are groups of specialised semiconductor devices for controlling the flow of electricity in power circuits. The BT139B-800,118 is a type of Thyristor – a Type 1 Silicon Controlled Rectifier (SCR) – specifically designed for Inverter and Motor speed control applications.

In essence these devices are robust and versatile switches that switch on when a certain voltage is applied, and can be used to switch other electrical components and systems on and off. BT139B-800,118 devices require only low power triggering to switch, and can switch on and off up to 4 times a second.

The BT139B-800,118 offers good surge current handling capabilities and enhanced reliability in high temperature and vibration environments. It has a relatively low forward voltage drop and low gate current. Its high power dissipation capability makes it especially suited for applications involving frequent switching and non-linear loads.

Applications

The BT139B-800,118 is ideal for use in motor speed control applications such as automatic door openers, air conditioners, washing machines, and other household appliances. It can also be used in low voltage inverter circuits, soft starters, and power factor correction circuits. In addition, the BT139B-800,118 can be used in high frequency switching applications such as radio frequency (RF) circuits, thyristor phase-control circuits, and signal-switching systems.

Working Principle

Thyristors are voltage controlled devices that can be used to control the levels of electric current that flow between two points in a circuit. The BT139B-800,118 is a device known as a Bidirectional SCR (Triode AC Switch), or TRIAC. This type of device allows current to flow in both directions when a suitable gate signal is applied. A TRIAC is essentially three rectifiers connected together in an alternating pattern. The first is a positive silicon controlled rectifier, the second is a negative silicon controlled rectifier and the third is a positive or negative extension, depending on the voltage at the gate.

When a voltage is applied to the gate, the quasi neutral region of the TRIAC shifts, allowing current to flow through it. This, in turn, allows the TRIAC to function as an electrical switch in AC circuits, providing the ability to turn a load on or off in any portion of the AC cycle.

In conclusion, the BT139B-800,118 is a powerful, reliable and versatile solution for controlling the flow of electricity in power circuits. Designed for invertor and motor speed control, it has an impressive power dissipation capability, low forward voltage drop, and low gate current for greater efficiency. The BT139B-800,118 can be used in a variety of applications ranging from household appliances to inverters and power factor correction circuits.

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