Production operating manual of electric motors

Asynchronous single-speed short-circuited electric motors of 380 volts are used to the drive of the pumping equipment and forced-draft mechanisms in boiler rooms, as a rule.

Rated parameters of electric motors are the power, tension, current, rotational speed and electrical power factor. Ratings of the electric motor are specified on the guard (name plate) which fastens to its body.

Типы станций управления электродвигателями

Types of stations of control of electric motors.

1. Admissible operating modes of electric motors.
1.1. Engines allow long work with the rated load at voltage deviation from rated ranging from +10 up to-5%.
1.2. Rated temperature of the entering air for electric motors +40 °C are considered. Engine capacity, at the temperature of the cooling air above rated, has to be reduced. Minimum temperature of the entering air is not normalized. Maximum permissible exceeding of temperature of parts of the engine at the ambient temperature of +40 °C for classes of isolation "And": windings - 60 °C; active steel - 60 °C, for isolation of the class "B": the winding and active steel - 80 °C. Maximum permissible temperatures of parts of the engine are equal to top admissible temperature for this part plus rated ambient temperature.
1.3. For rolling bearings maximum permissible temperature is equal to 100 °C. In most cases actual temperature is much lower than this size. If temperature of bearings considerably increased in comparison with is long the observed temperature, and temperature of engines and fresh air remained at the previous level, then it indicates emergence of defect in the bearing.
1.4. The admissible amplitude of vibration of the engine measured on each bearing should not exceed at rotating speed 3000 RPM. 0,05 mm, and at rotating speed of 1500 RPM. - 0,01 mm. The increased vibration increases wear of bearings, graze of the rotor for the stator, breakdown of the shaft of the rotor, violation of contact in windings is possible.
1.5. The cold engine with the short-circuited rotor is allowed to start up 2-3 times in a row, hot - not Bol 2 the time in a row as at the large number of start-up in a row, windings of engines inadmissibly overheat from the starting current that sharply reduces service life.
2. Supervision and care of engines.
2.1. Supervision of loading of engines, temperature of bearings and the cooling air, maintenance of level of lubricant in bearings and also start-up and the stop of engines is carried out by the personnel servicing the mechanism. The personnel of service of the chief power engineer are OBLIGED: to periodically examine electric motors, to control the mode of their work on all indicators, to make repair and tests.
2.2. Supervision and care of bearings of engines consists in control of their temperature and lack of the increased noise. Change of lubricant in rolling bearings is made, as a rule, once a year.
2.3. Supervision and care of cooling of engines consists in regular cleaning of the inhausting apertures of edge covers of engines of dust and dirt
3. Malfunctions of electric motors and their reason.

Схема работы электродвигателя

Scheme of operation of the electric motor.

3.1. At inclusion the electric motor does not rotate, hoots, or rotates, but very slowly. There can be several reasons:

3.2. During the operation of the engine the increased heating of rolling bearings is found. There can be several reasons:

  1. Lack of lubricant as a result of effluence or drying because of untimely replacement.
  2. Excesses of lubricant. Usually this of defect is observed after repair. It is necessary to reduce amount of lubricant what it would occupy volume no more than 2/3 free spaces.
  3. Emergence of defects in the bearing: sinks, operations of bodies of swing, destruction of the separator and graze it for the bearing holder. Emergence of sinks, cracks, developments in effective areas, holders, on balls or rollers of bearings is followed by emergence of the increased noise at rotation of the bearing. The engine has to be stopped for repair as soon as possible.
  4. Operation of the separator is found on availability of traces of metal (blestok) in lubricant and also on noticeable shrinkage of the separator down, with contact of holders.

3.3. During the operation of the engine the increased heating of its body is found. Possibly several reasons:

  1. Engine overload on current. For decrease in loading it is necessary to cover the pressure head latch on forcing of the pump or the regulating gate on the forced-draft mechanism.
  2. Swamping by dirt and dust of protective grids in edge boards from the supply of the cold air.
  3. Swamping by dirt and dust of ventilating channels in steel of the stator and the rotor.
  4. Violation of isolation between sheets of steel of the stator.
  5. During the operation of the engine from it sparks and smoke appear. Protection does not work. The most probable cause - graze of the rotor for the stator. It is necessary to switch-off the electric motor abnormally.
  6. Break of the chain of the stator during the operation of the engine. The engine will continue to work. At the rated load current in one phase will become equal to zero, in two others will increase. In order to avoid overheating and overheating of windings of the stator the engine should be switched-off.
  7. Strong vibration. At emergence of the vibration exceeding norm, the engine has to be removed in repair as soon as possible, and at the strong and increasing vibration the engine has to be stopped abnormally.
  8. At accident with people or breakdown of the drive mechanism the electric motor is switched-off from network. If there was the emergency shutdown of the electric motor, put into operation the electric motor of the reserve unit.

Repeated turning on of automatically switched-off electric motor is made only after its survey. If at automatic shutdown of the electric motor of the responsible mechanism inclusion reserve is impossible, then turning on of the switched-off electric motor is allowed after survey.

With strong indications of the short circuit, accidents with people or breakdown of the mechanism turning on of automatically switched-off IS FORBIDDEN electric motor.

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