Usually we use box type brush holders in all D.C. machines.At the outer end of arm a brush box is provided which is open at top and the bottom is attached.The brush is pressed to the commutator by means of a clock spring and this pressure could be adjusted by a level arrangement in the spring.The brush is connected to a flexible conductor called pigtail.The flexible conductor may be attached to the brush by a screw or may be soldered.

Brush boxes are generally made of bronze casting or sheet brass.For small machines working on low voltage commutation conditions are easy and galvanized steel boxes are employed.There are individual and multiple brush holders available on the market.In multiple brush holders a number of single brush holders are built into one long assembly.

Brush Rockers

Brush holder are connected or fixed to brush rockers with bars.The brush rockers arranged concentrically round the commutator.Cast iron is is usually used for brush rockers.

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