Carbon brushes

       Carbon brush (“motor brush”)

 A brush is a device that conducts current between stationary wires and moving parts, most commonly in a rotating shaft                                                                                

A carbon brush can be

1. Made of one or more carbon block

 2.  Equipped with one or more terminals


                           Functions of Carbon Brush

Carbon brushes are electromechanical conducting devices that connect to moving parts to provide an electric current. They are typically used in motors, generators, and alternators. Many carbon brush uses exist, but the three basic uses are in

     1. Household applications that run on alternating current (AC),

     2. Automotive applications that run on direct current (DC) and

3. Industrial applications that run on both AC and DC.

Working principle of Carbon brush's:

A carbon brush, also known as a motor brush is the small part of the motor that conducts electrical current between the stationary wires (stator) and the rotating wires (rotor) of a motor or generator. A motor generally contains more than one carbon brush to conduct electrical current.


                            FRICTION COEFFICIENT

Carbon brush friction coefficient “μ” has to be low and stable over time to allow the carbon brush to work without overheating.

  “μ” has no fixed value. It is the result of many factors depending upon   the carbon brush grade, speed, load, commutator (or slip ring)condition and environment.


“μ” friction coefficient calculation formula

The “μ” friction coefficient is the relationship

                     

Consider four types of Mechanical Parameters present in Carbon brush:

a.     SLIP RING AND COMMUTATOR SURFACE CONDITIONS (ROUGHNESS

b.     FRICTION COEFFICIENT

c.      VIBRATION

d.     CARBON BRUSH PRESSURE ON A SLIP RING OR COMMUTATOR

 

Consider three types of Electrical Parameters present in Carbon brush:

  a. VOLTAGE DROP (OR CONTACT DROP)

   b.  DISTRIBUTION OF CURRENT IN THE BRUSH CONTACT SURFACE

   c. RESISTIVITY

 Consider two types of Physical and chemical Parameters present in Carbon brush:-3

a. HUMIDITY      b. DUST 

Types of Carbon brush

 


Carbon brush common shapes





 


                                                                                                                            










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