【Q&A Question 087】2016.07.16

(1) Friction occurs between the rotor and the stator; for example, if the bearings lack oil, wear of the bearings causes the rotor to sink and come into contact with the stator； (2) The cooler air ducts are blocked or the inlet air temperature is too high, resulting in poor cooling of the motor ； (3) Coolant air entering steam or water causes the motor to become damp, reducing its insulation ； (4) Mechanical overload on the motor ； (5) Two-phase operation of the motor.

1. The motor is operating under overload conditions； 2. Motor short circuit ； 3. High temperatures

1 The motor bearing temperature is high. 2 The motor load increases. 3 Motor bearings are out of alignment.

Overpressure, superfluidity, bearing failure, ambient temperature, cooling fan, etc

There are short circuits between the turns of the motor windings, between windings of different phases, and between the windings and ground, which causes an increase in current within the windings and leads to a sharp rise in temperature, resulting in overheating. 　　2. The insulation between the motor core laminations is damaged, resulting in increased eddy current losses within the core; this leads to a sharp rise in core temperature and excessive heating. 　　3. When a three-phase motor operates with one phase missing, the current in the other two phases increases, resulting in excessively high winding temperatures. Similarly, when a starting winding in a single-phase motor is broken, the temperature of the main windings also rises excessively. 　　4. Operating the motor under overload for an extended period can also lead to excessive winding current, resulting in increased heating of the windings and thus high temperatures. 　　5. If the motor is started too frequently, the current during startup is more than twice the normal operating current, which can also lead to increased heating of the windings and thus excessive temperatures. 　　6. Poor electrical contact in the motor leads to increased heating at the connection points, resulting in excessive temperatures. 　　7. When the grid voltage is too high or too low, it increases the current in the motor windings, resulting in heating and excessive temperature. 　　8. When the bearings in the rotating parts are damaged or lack lubrication, it increases friction in those rotating parts or leads to collisions, resulting in excessively high temperatures. 　　9. A malfunction in the motor’s cooling components or blockage of the ventilation channels leads to excessive temperatures. 　　10. The ambient temperature is too high when the motor is in operation.

The main reasons are as follows: (1) Friction occurs between the rotor and the stator; for example, lack of oil in the bearings, or wear and damage to the bearings cause the rotor to sink and come into contact with the stator； (2) The cooler air ducts are blocked or the inlet air temperature is too high, resulting in poor cooling of the motor ； (3) Coolant air entering steam or water causes the motor to become damp, reducing its insulation ； (4) Mechanical overload on the motor ； (5) Two-phase operation of the motor.

Motor fan has fallen off, coil is damaged, excessive vibration

Lack of lubricating grease, excessive power