Montage et ajustement d'arbres, de roulements et de coussinets ESA-OFPPT-PDF
Data
Control of artificial round or "ovality" of the
collector.
It is done with a comparator whose base is supported on the
brush holder or the flange of the motor.
The measuring tip remains on the head of a broom which will
be versatile under the effect of a possible (oval) defect in the collector. The
brush movement must not exceed 0.03 mm.
Roughness control of the collector lamellae
If a roughness controller is arranged, it must be checked
that the condition of the surfaces of the collector lamellae are:
· From 1 to 1.8 µm for motors with power> 1.5 kW
0.5 to 1 m for motors with power <1.5 kW
Brush holder crown adjustment.
After replacing a collector, the position of the brushes
must be adjusted if they are mounted on an adjustable crown. Place a voltmeter
as on the diagram below (scale of a few volts).
Connect and disconnect a heap on the stator so as to
generate an induced strain between the brushes of the collector, the motor
driving in dynamo. The right position is obtained for a brush tension as low as
conceivable.
Brush holder crown adjustment
Continuity check of a DC stator
It is done with the ohmmeter the two test probes being
affixed between the focuses of associations of the terminal block. We must
measure a few tens to a hundred ohms.
The standard insulation affinity to the stator frame must
also be measured.
Insulation check
The insulation must be at least 5 M pour for a test strain
of 100 volts (i.e. 5,000ω / volt)
Towers short circuit control
It is done with the engine disassembled with a tester (also
called grognard). It is in fact a coil whose open magnetic mass closes by
relation to the notches of the motor. A transformer is thus obtained, the rotor
or stator coil being the secondary. A short circuit in a tower of this
secondary increases the current of the primary which is signaled by a noise or
an indicator light.
Renovation of a DC motor
In the event of renovation of a DC motor the following
operations must be carried out in a specialized workshop:
Disassembly of the coupling present on the motor
· Removal of brushes and brush holder springs
· Complete disassembly of the engine and markings
· General cleaning and degreasing of mechanical parts
· Control and measurement of the tolerances of the bearing
seats on the shaft and in the flanges
· Armature cleaning using an appropriate detergent
· Oven drying with forced air
· Electrical control of the rotor winding
· Winding continuity tests
· Measuring the value of insulation
· Search for bad welds from the winding to the collector
· Short circuit searches between towers, entry to controller
(grognard)
Armature vacuum impregnation and oven varnish polymerization
· Rectification of the collector at the visit
· Milling of mica between blades and chamfering the blades
· Dynamic balancing of the armature on a balancing bench
· Cleaning of the windings of the head and auxiliary field
· Drying in a forced air oven
· Coil timing control and electrical winding control
· Varnishing the stator and armature windings with hostile
red varnish to streak
· Replacement of bearings
· Repair and adjustment of brush holders - running in
brushes
· Reassembly of the engine - fight tests or tests on a test
bench
· Finishing and painting, reassembly of the coupling.
Tree control
The bending of the shaft is particularly to be watched, an
excessively specialty load applied on the child end can generate a torque such
that a bending evaluate occurs.
is induced and worn on the bearings or causes the rotor and
stator to rub.
This bending results in a weakness of the shaft, a bad
positioning of the brushes, an excessive exertion on the bearings according to
an inappropriate edge and in extreme cases a contact between the magnetic
sheets and the magnets.
Occasionally, the shaft deformation should be checked with a
comparator. It is conceivable on certain motors to separate the axis of the
rotor and to replace it. The tolerance will be from one to a few hundredths of
a mm.