AC may convert to DC by following ways
1) The most conventional way to convert AC into DC is by rectifiers and filter circuits.
A rectifier is an electrical device that converts alternating current, which periodically reverses direction, to direct current, which flows in only one direction. The process is known as rectification since it “straightens” the direction of the current.
2) Unconventional conversion of AC to DC
AC motor coupled to DC generator
This system may be used for high power, where a huge amount of current involved in the conversation. System has low efficiency.
3) Thyristor converts AC into controlled DC output
A thyristor needs a triggering pulse at the gate, when forward biased, to conduct. By controlling the triggering (firing) angle, the output dc voltage can be controlled effectively. A single-phase full-wave controlled bridge ac to dc converter, rectifier, using thyristors is presented in this paper.
4) Mercury arc rectifier valves used for industrial purposes
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5) Electrolytic rectifier
The electrolytic rectifier operates on the principle that an aluminum electrode in an electrolyte will only conduct when it is negatively charged. When it is positively charged, it quickly forms an insulating layer of aluminum oxide which prevents further current flow. When it is negatively charged, it forms hydrogen at the surface of the electrode, which disturbs the oxide layer enough to allow current to flow.
6) vibrating rectifier
These consisted of a resonant reed, vibrated by an alternating magnetic field created by an AC electromagnet, with contacts that reversed the direction of the current on the negative half cycles. They were used in low power devices, such as battery chargers, to rectify the low voltage produced by a step-down transformer.