Lenze MGXQK DC motors - Manual (Page 18)

18
7.4 Recognition of incorrect operating
conditions
The function of the collector and the carbon
brushes is influenced by many factors. For
example humidity, pollutants in the air in the
form of gases, oil or solvent spray etc. as well
as a very low temperature of the cooling air,
low loads over a long time or vibrations acting
on the motor are decisive factors for the
commutation and wear of collector and
carbon brushes.
A prerequisite for a good function of the
carbon brushes is the right choice of the
brush material and the correct total
cross--section of the carbon brushes of each
pole, which must be perfectly adapted to the
motor and the operating conditions of the
motor.
Lenze have a long experience in
manufacturing motors and selecting optimum
carbon brushes. For special operating /
ambient conditions the brush material and the
number of carbon brushes can be adapted
for an optimum wear.
Before selecting another type of carbon
brushes, always contact the Lenze Service.
In the following, some troubles, possible
causes and measures to improve the
commutation and the wear are listed:
Fault Cause Remedy
Sparking,
increased brush wear,
black coarse spots on the collector s rface Penetration of oil or oil spray Avoid penetration of oil into the collector area
by sealing
black, coarse spots on the collector surface
Remove pollutions
Slightly grind the collector and thoroughly
clean carbon brushes
Sparking,
chatter marks on collector and carbon brush
r nning s faces Solid dust particles under the carbon brushes
cause chatter marks Where necessary, ensure efficient protection
against dust using filter elements
running sufaces
Supply motor with clean cooling air via a tube
system
Sparking,
collector surface has the colour of copper,
increased wear Formation of patina impossible because of
very dry air Increase humidity by air-conditioning of the
operating rooms or by other measures
Insufficient or missing patina,
run-in marks at the collector Temperature of the collector surface and the
carbon brushes too low for the formation of
patina Increase ambient temperature and thus the
cooling air temperature
Very low cooling air temperature or motor
operation with a considerably lower load
current than the rated current over a long time Reduce carbon brushes according to the load
Contact the Lenze Service
Strong sparking,
bl e or green lights High motor overload Reduce motor load
blue or green lights,
burns at the bar edges and chipping at the
edges of the carbon brushes
Check field supply,
measure armature current and adapt to the
rated current
Sparking,
excessive wear of carbon brushes,
collector with clear chatter marks Operation in rooms with chemically polluted
atmosphere Supply motor with clean cooling air using
suitable filter elements or supply of external
fresh air
Sparking,
burnings at the collector,
increased wear Insufficient contact between carbon brushes
and collector Clean collector in regular intervals
increased wear
Acumulation of carbon dust and other
pollutants Check if carbon brushes can easily slide in the
brush holders
Missing pressure Ensure easy sliding of the carbon brushes with
continuing wear
Reduction of the pressure by high accelerations Fit stronger springs in the motor
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