Machine Tools: Lecture 3

Induction motor

• expensive

• used DC current

• asynchronous motor

• synchronous motor

Write down only one (1) character of electric motor. (all in small letter with a space if two sentences. Example: abc def)

From this figure, what is the value of torque developed by the induction motor when speed of rotating magnetic field equal to zero?

• critical

• 1

• zero

• nominal

From this figure, it can be concluded that:

• With the motor in operation, the resistance of rheostat 1’ can be increased

• third method of speed changing - by changing the input of the current

• The rheostat resistance being increased, the exciting current and magnetic flux are reduced

• the number of rheostat steps is large, motor speed changing becomes more rigid

From this Ward-Leonard system, it can be observed that:

• The system used in heavy and high-power machine tools with infinitely constant speed or feed are required.

• The function of Rheostat 6 is to control the magnetic flux of generator 3

• The switch controlling the direction of current in the exciting winding of generator 3

• The speed of motor 4 can be varied by changing the input voltage fed into motor 3 with the aid of rheostat 6 (by changing the magnetic flux of generator 2);