Rectifiers used for welding duty:

There are various types of rectifiers used for welding duty, but the rectifier commonly used for this purpose is selenium metal rectifiers.

Explanation:

Rectifiers:
Rectifiers are electrical devices that convert alternating current (AC) into direct current (DC). They are essential components in many electrical and electronic systems, including welding machines.

Welding Duty:
Welding duty refers to the duty cycle or the percentage of time a welding machine can be operated continuously before it needs to cool down. Duty cycles are expressed as a percentage, usually ranging from 10% to 100%. For example, a welding machine with a 60% duty cycle can be operated for 6 minutes out of every 10 minutes.

Rectifiers for Welding Duty:
When it comes to welding duty, the rectifiers used should be able to handle the high current demands and provide stable DC output for efficient welding operations. The rectifiers commonly used for welding duty are:

- Mercury Arc Rectifiers:
Mercury arc rectifiers were widely used in the past for welding duty. They consist of mercury vapor-filled tubes that rectify the AC current. However, mercury arc rectifiers have several drawbacks, including environmental concerns due to the toxic nature of mercury.

- Selenium Metal Rectifiers:
Selenium metal rectifiers are the rectifiers commonly used for welding duty. They are solid-state rectifiers that use selenium as the rectifying material. Selenium rectifiers are known for their high current-carrying capacity, reliability, and durability. They can handle the high currents required for welding operations and provide stable DC output.

Conclusion:
In conclusion, for welding duty, the rectifier commonly used is selenium metal rectifiers. Selenium rectifiers are preferred due to their ability to handle high currents, reliability, and durability. They provide stable DC output for efficient welding operations. However, it is important to note that with advancements in technology, other types of rectifiers such as silicon rectifiers have become more prevalent in modern welding machines.