Rotary Converters

The ac and dc armature powers will be equal when :

(i) losses are neglected.
(ii) power factor is unity.







In that case the ratio of slip ring (line Current) to the dc output current will be

I_L / I_D = (2 √ ( 2 ) ) / N

Where

N is the number of slip rings.

N	Ratio IL/ ID
2	1.41
3	0.94
6	0.47
12	0.24

For efficiency η and power factor cos φ, the ratio will be greater by a factor 1/ η cos φ.

SI. No.	Particular	Rotary Converter	Metal plate rectifier	Mercury arc rectifier
1.	Construction	Very difficult to construct	Most easy to construct	Easy to construct as compared with rotary converter
2.	Operation	Requires great care at the time of starting	Its starting operation is most easy	Operation easier than that of rotary converter.
3.	Sound and vibration	Produces sound and vibration	Soundless and produces no vibration	No vibration and soundless operation
4.	Fault	Chances of occurring faults are more due to rotating machine	Less chances of faults in it	Very less chances of faults
5.	Rating	Can be manufactured for high rating only	Manufactured in both small and high capacity	It cannot be made in low capacity
6.	Cost	Initial cost if very high	Least costly	Initial cost is less than rotary converter.
7.	Maintenance	Needs great care and maintenance as it is a rotating machine	Requires less maintenance	Needs less maintenance as compared to rotary converter.
8.	Efficiency	Fair	Good	Good
9.	Life	Long	Long	Very long
10.	Application	It can be used as a dc motor, ac motor, converter and inverter. It is specially used in sub-stations to convert ac to dc.	It is used for battery charging, electroplating, electrolysis, etc.	It is employed in substation to convert ac to dc and is superceding the rotary converters.