Examens De Passage Électromécanique des Systèmes Automatisées-ESA-OFPPT-PDF
Examens De Passage
Degradation of bearings
This failure is the most frequent cause of intervention on AC motors
• The wear of the bearings is the cause of noise, vibrations. A bearing that has not been replaced in time may lock up, turn on the shaft or in the seat (in the flange) and thus damage these two elements. In this case, you will need:
• Replace the rotor or reload the shaft and correct it. A shaft span can be recharged either standard thermal spraying or standard welding followed by a heat treatment and then machined to the prescribed diameter.
• Replace the flange or reload the seats. A bearing seat seat can be reloaded as standard by adding a steel ring which is then machined to the prescribed diameter See the bearing support module
It causes premature degradation of the bearings or bearings, it can lead to deformation of the rotor shaft, a loss of efficiency of the installation.
Troubleshooting AC electric motors
A DC motor is often coupled to a standard variety of frequency drive which can itself be the cause of the failure. This drive must itself be checked in case of doubt.
Spectator in particular follows oil leakage or grease dripping on the bearings.
Check the tightness of the legs or ladies of obsession
Check for abnormal vibrations. V
Some consideration should be given to the following focuses:
• Has there been a change in engine orientation (Vertical / level or the other way around): is it designed for this? otherwise the bearings or stops will have to be changed too frequently. A bearing must last at least two years under hard conditions and in continuous operation.
• Has the motor already been rewound? when?
• Has there ever been a motor replacement, does the current motor comply with the initial recommendations? Was there a standard replacement for another model?
• Is the use of the trailing machine according to its real possibilities?
Check the following focuses
• Presence of leakage current which could eventually damage the bearings.
• Check the alignment of the motor, incorrect alignment deteriorates the bearings. (see chapter on bearing troubleshooting).
• Presence of dust, humidity, metallic particles and so on over the top by affinity to the engine class.
• Value of pressures and intensity absorbed.
• Is the motor protected by a thermal relay?
• Is the power cable segment sufficient considering the starting overcurrent?
Check for visible damage:
- Fan split, broken, lack of blades;
- Deformed or detached fan cover;
- Cracked obsession legs or damaged obsession lady of the hour.
- No accumulation of dust, filaments, shavings and other materials on the carcass or around the fan inlet
- No significant consumption on the lifting eye rings / bolts
- No excessive vibrations
- No loose fasteners
- Cables and earths in good condition
- Motor tightness and cable gland in good condition
- Adequate insulation resistance. It is important to carry out this check after an extended shutdown period.
- Possible lubrication, particularly for 2-pole motors (3000TM) of high power.
- General condition of the engine, child alignment and its transmission components (pulley, pinion, chain, belt).
- Standard wear thermal exhaustion of the winding wires, especially on the elbows. This thermal weakness occurs after ten years of use in discontinuous administration following expansion and retraction under the effect of thermal varieties.
Run the engine empty with the principle and check the absence of abnormal braking for small models.
Squirrel confinement rotor control
It may happen that a bar of the squirrel confinement is broken or unsoldered. This produces tower crack and vibration. This fault can be detected by standard advanced vibration control devices or by standard visual examination of the disassembled rotor.
Wound rotor control
Check the ohmic resistance between the rings. It should be a few ohms.
The two test probes are affixed to the rings on the ohmmeter. We must measure a resistance of a few ohms. A cut can be a bad weld at the connection of the ring with the winding wire. A solder can be apparently perfect but mask a pocket of resin or insulating oxide which surrounds the copper of the wire.
Demagnetization of rotor magnets
It may happen that a magnet loses its magnetic properties. It must then be replaced.
Bending the tree