MATTHIESEN Magic Finger Bagger, Owner'S Manual

Page: 56 / 85

Section 1
General Information
3-8 Maintenance & Troubleshooting MN605
Turning The Commutator
After commutator turning, check its run-out with the bearings on V blocks. For all
commutators, maximum run-out is .002
″
. New and minimum commutator diameters are
listed as follows.
Commutator Brush Track Diameters
Frame New Motor Commutator
Diameter (inches)
Minimum Diameter after
Refinishing (inches)
180 2.750 2.51
210 4.500 4.29
250 5.000 4.72
280 5.750 5.45
320 6.500 6.20
360 7.500 7.21
400 8.250 7.90
500 10.250 9.72
Notes:
The above diameters are approximate.
They are for standard design and speed motors. high speed motors require
larger minimum bar diameters. Contact Baldor for dimensions.
Commutator surface finish, after machining, should be between 40 and 65
micro-inch RMS.
Commutator Undercutting
Check the commutator mica between bars for an under-cut depth of 1/64
″
minimum,
5/64
″
maximum. The grooves of the under-cut are to be free of mica and chips.
Caution: Be very careful when repainting a drip proof motor. Do not get any
paint on the commutator. Paint on the commutator will show up as
black marks in brush tracks. Also, excessive brush sparking or
erratic operation can be caused by paint or other material on the
commutator.
Blowers & Filters
Do not use silicone RTV around DC motors as commutator surface damage can occur.
Intake filters on blowers and louvers of drip proof motors should be cleaned to remove
any dust or foreign matter. Canister type filters should be replaced when dirty. Failure to
keep air intakes clear will cause overheating and premature failure of the insulating
system.
Troubleshooting
Armature Overheating Excessive overloads will cause a noticeable odor of overheated varnish or charred
insulation. The commutator may eventually become blackened and pitted and the
brushes burned. This overheating may be general and uniform. To cure, remove the
overload and rewind or replace armature if damaged beyond use.
An open-circuited armature coil will cause flashing at the commutator. Two adjacent bars
will show severe burning and a resulting overheated armature. Short-circuited coils or
commutator bars may cause local heating that could destroy the insulation at that spot.
This may result in the burning of the armature coils, banding or commutator bars.
Grounds in the armature circuit may be found by using a megger. Connect one lead to
motor frame and the other lead to a commutator bar. If the armature is grounded, the
megger will show less than 1 meg ohm.
These tests should be done by experienced and qualified personnel.
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