TABLE OF CONTENT IN THIS BLOG
1. Introduction to Thyristor
2.Definition of Thyristor
3.History of Thyristor
4.Structure and Basics
5.Working Principle
6.Characteristics of Thyristor
7.Applications of Thyristor
8.Semikron SKKT 162/16E Dual Thyristor Module
- Terminals (1, 2, 3)
- Gate & Cathode Pins
- How It Functions
1. Introduction to Thyristor
Thyristors are one of the most important devices in power electronics. They are widely used for controlling high voltage and high current in AC and DC systems. From motor speed controllers to industrial rectifiers, thyristors are everywhere.
2. Definition of Thyristor
A thyristor is a semiconductor device made of four alternating layers (PNPN) with three terminals: Anode (A), Cathode (K), and Gate (G).
It works like a controlled switch.
- The gate signal turns it on.
- It stays on until the current naturally goes to zero (or is externally forced to zero).
3. History of Thyristor
The thyristor was invented in 1957 by General Electric (GE). Before that, bulky and less efficient vacuum tubes were used for power control. The invention of thyristors revolutionized power electronics, making systems smaller, cheaper, and more reliable.
4. Structure and Basics
A thyristor has:
- Anode (positive terminal)
- Cathode (negative terminal)
- Gate (control signal input)
Internally, it is like two transistors connected in a feedback loop, giving it the ability to latch once triggered.
5. Working Principle
- Without gate signal → remains OFF (blocking state).
- Apply a small gate pulse → device turns ON and allows current to flow from Anode to Cathode.
- It stays conducting until the current drops below a certain value (holding current).
6. Characteristics of Thyristor
- Latching: Once turned on, stays on.
- Holding Current: Minimum current to keep it conducting.
- High Power Handling: Can control thousands of volts and amps.
7. Applications of Thyristor
- Motor speed control
- Light dimmers and fan regulators
- Rectifiers and inverters
- Battery chargers
- Industrial heating systems
8. Semikron SKKT 162/16E Dual Thyristor Module
The Semikron SKKT 162/16E is a dual thyristor (SCR) module. Inside the block, there are two SCRs connected in opposite directions (anti-parallel). This setup makes it ideal for AC power control.
Terminal Functions
- Terminal 1 (AK / Anode of SCR1) – Current enters here when SCR1 is triggered.
- Terminal 2 (Common) – Acts as Cathode of SCR1 and Anode of SCR2.
- Terminal 3 (K / Cathode of SCR2) – Current flows out here when SCR2 is conducting.
So:
- SCR1 works between 1 → 2
- SCR2 works between 2 → 3
Gate & Cathode Pins
- G1 & K1 → Trigger SCR1 (path 1 → 2).
- G2 & K2 → Trigger SCR2 (path 2 → 3).
How It Functions
- Without gate signal → both SCRs OFF (blocking state).
- Gate pulse to SCR1 → current flows 1 → 2.
- Gate pulse to SCR2 → current flows 2 → 3.
-
AC Control:
- Positive half cycle → SCR1 conducts.
- Negative half cycle → SCR2 conducts.
- Together, they provide smooth AC control.
In Simple Words
- Gate = switch button
- Anode = entry point of power
- Cathode = exit point of power
- Terminals 1, 2, 3 = power path
- Small pins = control signals
This way, the SKKT 162/16E module can handle large AC power while being controlled by a tiny gate pulse.
9. Advantages and Limitations
- ✅ High efficiency
- ✅ Handles large voltage/current
- ✅ Compact and reliable
- ❌ Cannot be turned off by gate (for SCR type)
- ❌ Slower switching compared to modern transistors
10. Conclusion
Thyristors are the backbone of power electronics. From simple fan regulators in homes to heavy industrial drives, they play a vital role in controlling electrical energy. The Semikron SKKT 162/16E module is a practical example that shows how two thyristors can be combined to control AC power efficiently.
