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Brush Chatter

P2	P22	P42	P4	P6	P24	P16	P46

P12	P28	P26	P12

Sparking at the Leading Edge

B2	B6	B8	B10

Cummutator has Wavy Pattern

T12	T10	T14	T16	T18

Cummutator has Unsymmetrical burn marks

R2	R4

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1)	Film
	P2, P4, P6 good appearance, uniform colouring from bright- to darkbrown

2)	Appearance of patina
	P12	streaky film, not uniform - no copper wear
		causes : too much humidity, oil vapours, gases, current density, too low in brushes
	P14	streaky film, insufficient patinated copper, commutator wear
		causes : like P12, but long lasting damages - check brush grade
	P16	film with patchy colours - uneven film
		causes : Commutator out of round or dirty; perhaps vibration or mechanical deficiences

3)	Marks of mechanical origin
	P22	These areas can be isolated or regular
		causes : Commutator out of round, vibrations due to wrong balancing, worn bearings
	P24	dark marks with straight edges, followed by brighter ones with smudged edges
		causes : faulty lamella or group, which may result in brush lifting
	P26	lamellas are spotted either in the centre or on the edges
	P28	causes : high mica, low bars on entring on leaving edges, poor commutator machining
	P42	light/dark bar pattern - polished, matt or carbonized appearance
		causes : related to winding design of armature - difficulty caused from split windings crossing in the same slot
	P46	dark marks of varying densities and shape, matt or carbonized, appear in distance of a double pole sharing
		causes : faulty soldering connections on coils or terminals

4)	Burns
	B2-B6	Burns caused by brush fire on the bar edges - pay special attention!
	B8	twins in the centre of bars
	B10	perforated patina, small light spots on commutator film due to sparking under brush

5)	Marks
	T10	dark spots correspond to brush contact surface
		causes : long periods of operation at low or no load
		dark marks result from high bards (L2)
		dark marks result from low bars (L4)
		dark marks result from proud mica (L6)
		dark marks result from burrs (L8)

6)	Faulty commutator segments
	L2	high
	L4	low
	L6	proud mica
	L8	burs on the bar edge
	L10	copper dragging

7)	Wear of commutator segments
	R2	axle sectional view of bar - normal wear of copper per section and correct brush stagger
	R4	bar shows unnormal wear - wrong brush stagger, wrong grade and pollution


Possible Causes