Thyristors

Thyristors are four-layer semiconductor devices, also known as a silicon controlled rectifier (SCR) It is like a fast static switch and is good for controlling large amounts of power, they can also control the speed of DC motors. You can learn more in our complete guide to thyristors.

How do thyristors work?

Thyristors usually consist of three electrodes: an anode (positive terminal), Cathode (negative terminal) and a gate. (You can also get thyristors with two or four leads). The gate is the main control terminal while the main current flows between the anode and cathode Thyristors are made of N-type and P-type materials. The N-type material is formed by doping an element with electrons to increase the number of negative charge-carrying electrons. The P-type material is also produced through doping, although the resulting charge-carrying electrons are positively charged. By alternating layers of P and N-type material, a semiconductor thyristor device is formed. Thyristors are used to create a latching circuit. Thyristors can be turned on using the gate. It then turns off when the voltage across the anode-cathode drops back down to zero.

Types of thyristors

  • Silicon controlled rectifier (SCR) - The basic purpose of an SCR is to function as a switch that can turn on or off small or large amounts of power.
  • Silicon controlled switch (SCS) - Silicon Controlled Switch (SCS) is a device similar to an SCR, but it is designed to turn off when a positive voltage/input current pulse is applied to an additional "Anode gate".
  • Triac - Triac gets its name from Triode for alternating current Triacs are similar to SCRs but it conducts in both directions, (a bidirectional device). This means that it can switch AC and DC currents., Firing circuit commander modules are required for this.
  • Four-layer diode - A four-layer diode has 2 pins and is similar to a voltage-sensitive switch. When the voltage between the two pins exceeds the breakdown voltage it turns ON, otherwise its OFF.
  • Diac - Diac is a mix of the words diode and ac switch it is similar to a four-layer diode but it can conduct in both directions meaning it can contact both AC and DC currents.

Applications of thyristors

Thyristors are commonly found in many everyday applications such as:

  • Motor speed controls
  • Pressure control systems
  • Light dimmers
  • Liquid level regulators

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Description Price Rated Average On-State Current Thyristor Type Package Type Repetitive Peak Reverse Voltage Current Rating Surge Current Rating Mounting Type Power Rating Maximum Gate Trigger Current Output Isolation Input Voltage AC Maximum Gate Trigger Voltage Input Voltage DC Maximum Holding Current
RS Stock No. 165-2391
Mfr. Part No.VS-50RIA120
BrandVishay
£14.015
Each (In a Bag of 100)
Units
50A SCR TO-65 1200V - 1490A Thread Mount - 100mA - - 2.5V - 200mA
RS Stock No. 395-3474
Mfr. Part No.VS-50RIA120
BrandVishay
£20.18
Each
Units
50A SCR TO-65 1200V - 1490A Thread Mount - 100mA - - 2.5V - 200mA
RS Stock No. 379-8031
Mfr. Part No.VS-T90RIA120
BrandVishay
£32.95
Each
Units
90A SCR D 55 1200V - 1870A Panel Mount - 120mA - - 2.5V - 200mA
RS Stock No. 165-2605
Mfr. Part No.VS-T90RIA120
BrandVishay
£28.397
Each (In a Box of 10)
Units
90A SCR D 55 1200V - 1870A Panel Mount - 120mA - - 2.5V - 200mA
RS Stock No. 159-6487
Mfr. Part No.VS-P402W
BrandVishay
£30.151
Each (In a Box of 10)
Units
40A SCR Module PACE-PAK 600V - 0.4kA Screw Mount - 60mA - - 2V - 130mA
RS Stock No. 700-5611
Mfr. Part No.VS-P402W
BrandVishay
£32.30
Each
Units
40A SCR Module PACE-PAK 600V - 0.4kA Screw Mount - 60mA - - 2V - 130mA
RS Stock No. 145-1945
Mfr. Part No.VS-25RIA120
BrandVishay
£11.526
Each (In a Bag of 100)
Units
25A SCR TO-48 1200V - 440A Thread Mount - 60mA - - 2V - 130mA
RS Stock No. 254-0544
Mfr. Part No.VS-25RIA120
BrandVishay
£15.59
Each
Units
25A SCR TO-48 1200V - 440A Thread Mount - 60mA - - 2V - 130mA
RS Stock No. 700-5620
Mfr. Part No.VS-P405W
BrandVishay
£35.78
Each
Units
40A SCR Module PACE-PAK 1200V - 0.4kA Screw Mount - 60mA - - 2V - 130mA
RS Stock No. 169-5838
Mfr. Part No.50RIA60
BrandVishay
£10.40
Each (In a Bag of 100)
Units
50A SCR TO-65 600V - 1490A Thread Mount - 100mA - - 2.5V - 200mA
RS Stock No. 165-2948
Mfr. Part No.VS-P405W
BrandVishay
£27.622
Each (In a Box of 10)
Units
40A SCR Module PACE-PAK 1200V - 0.4kA Screw Mount - 60mA - - 2V - 130mA
RS Stock No. 227-9107
Mfr. Part No.VS-50RIA60
BrandVishay
£11.96
Each
Units
50A SCR TO-65 600V - 1490A Thread Mount - 100mA - - 2.5V - 200mA
RS Stock No. 159-6605
Mfr. Part No.VS-81RIA120PBF
BrandVishay
£29.258
Each (In a Bag of 25)
Units
80A SCR TO-209AC 1200V - - Thread Mount - 270mA - - 3.5V - 200mA
RS Stock No. 873-2314
Mfr. Part No.VS-81RIA120PBF
BrandVishay
£33.13
Each
Units
80A SCR TO-209AC 1200V - - Thread Mount - 270mA - - 3.5V - 200mA
RS Stock No. 169-5900
Mfr. Part No.VS-25RIA120M
BrandVishay
£9.321
Each (In a Bag of 100)
Units
- - - - - - - - - - - - - -
RS Stock No. 395-2869
Mfr. Part No.VS-25RIA120M
BrandVishay
£10.25
Each
Units
25A SCR TO-48 1200V - 440A Thread Mount - 60mA - - 2V - 130mA
RS Stock No. 169-5784
Mfr. Part No.VSKH142/12PBF
BrandVishay
£50.513
Each (In a Box of 15)
Units
140A SCR IPAK (TO-251) 1200V - 4712A Panel Mount - 270mA - - 4V - 200mA
RS Stock No. 301-300
Mfr. Part No.VS-VSKH142/12PBF
BrandVishay
£58.91
Each
Units
140A SCR IPAK (TO-251) 1200V - 4712A Panel Mount - 270mA - - 4V - 200mA
RS Stock No. 227-9258
Mfr. Part No.VS-VSKT250-16PBF
BrandVishay
£179.74
Each
Units
250A SCR MAGN-A-PAK 1600V - 8.9kA Panel Mount - 350mA - - 4V - 500mA
RS Stock No. 817-2453
Mfr. Part No.VS-50RIA20
BrandVishay
£11.48
Each
Units
80A SCR TO-65 200V - 1490A Thread Mount - 250mA - - 3.5V - 200mA