The primary function of the brush involves conducting current. In many cases the brush holder is also a part of this electrical
circuit.Therefore it is necessary that all electrical connections are of minimal resistance to provide the best path for current flow
from the main lead connection to the contact surface. Corrosion, contamination, or electrolytic action over a period of time can
cause dramatic increases in resistance which then requires cleaning. Careless installation of the brushes or the holders can
lead to loose connections. Any high resistance in the brush circuit will result in excess heat or an undesirable path of current
flow and unequal loading of the brushes.
On fractional horsepower cartridge style brushholders with captive coil spring type brushes the current should flow from the
clip connector at the bottom of the holder up the brass insert to the cap on the end of the brush and then down through the
shunt to the carbon. The brushes fail very quickly if the round or eared cap on the end of the brush does not make proper
contact with the brass holder insert. When this condition exists current will flow directly from the brass insert to the spring or
to the carbon. In either case there will be extreme heat, loss of brush contact, commutator wear, and eventually motor failure.
Another problem with larger frame sizes can occur when the holder mounting is part of the electric circuit. If the holder
mounting surface becomes dirty, corroded, or even painted over then current will again need to follow another path and
thereby cause problems.Anyway click here for more info www.ttmotor.com Thank you !