Motors/Bearings

Question 1

Briefly describe the procedure for Removing a worn bearing from a motor shaft

Answer 1

: Should carefully be removed using bearing pullers Heating the bearing should make easier

Question 2

Briefly describe the procedure for Replacing a bearing on a motor shaft

Answer 2

:New bearing is fitted using power press and a pipe that puts pressure on the inner bearing race only

Question 3

Where would a thermistor be located in the over current protection circuit of a three phase induction motor

Answer 3

The thermistor would be embedded in the windings of the motor connected to a control relay

Question 4

Name two methods of coupling motors to drive a given load

Answer 4

1. solid coupling
2. flexible coupling
   3.vee-belt drives
   4.flat belt drives

Question 5

Flexible couplings are used on electric motor drives state clearly the basic function of such flexible coupling and state how to motor is aligned to its load

Answer 5

The function of a flexible coupling is to mechanically connect a motor to its load when motor shaft and load shaft are connected end to end
The centre of both shafts lie approximately along the same centre line

Question 6

Describe two advantages a flexible coupling offers the user when it is used to connect a mechanical load to an electric motor

Answer 6

1. The motor does not need to be in perfect alignment with the mechanical load
2. the coupling can absorb some of the sock if stated suddenly
3. The coupling can accommodate shift expansion
4. The coupling can absorb vibration in motor or load