Montage et ajustement d'arbres, de roulements et de coussinets ESA-OFPPT-PDF
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.
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.
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.