The document discusses different methods for starting electric motors, including direct-on-line start, star-delta start, and using rotor resistance or a soft starter device. Star-delta start has disadvantages like lower starting torque and requiring six motor terminals. Rotor resistance starting provides higher torque but cannot be used with squirrel cage motors. Soft starter devices provide gradual voltage increases, reducing mechanical shocks and current spikes while maintaining the network voltage, at the cost of higher price.

3. 1- Direct-on-line start (D.O.L):

6. 2- star- delta method:

9. *disadvantage of star- delta method:
1-decreasing in starting torque about (25-
30%)of normal torque
2-must be terminals six of motor available for
connection
3-transint in voltage by two steps(220-380v) not
soft in operating
4-constant starting voltage where not control in
voltage

34. • Rotor resistance:

37. *It not depend on decrease in voltage but
depend on input resistors in the rotor
• Advantage:
1- high starting torque
2-give more stating soft (more steps)
3-part of starting energy convert to heating in
resistors far of motor
• Disadvantage:
1-not use with squirrel cage motor
2- contentions energy losses in resistors not
useful

44. • Advantages:
1-decraesing mechanical shocks on rotor and
gears
2-decraesing in starting current for motor
windings
3-keep up on network voltage constant
4-decraesing the dangerous on distribution
transformer
5-safe electrical energy at starting

45. 6-prevent the Suddenly shocks during raise the
load by cranes
7- not need to maintenance
disadvantages:
-high cost

55. * Questions about soft starter device:
• What are the components of soft starter
device:
• What are the specifications that are required
by the soft starter device:
• Can use device differ rated (v ,I) from rated (v
,I) motor :
• Can use one device with several motors:
• Can use device with synchronous motor: