The document discusses motor starting methods and their associated starting currents. It describes direct-on-line starting as having the highest starting current at 6 times normal current. Star-delta starting has a starting current of 3 times normal. Soft starters have a starting current of 2 times normal. The document also discusses star and delta motor connections, overload protection for motors, and provides examples of motor control circuits.

1. Motor starting
BY: Mahmoud Hussein

2. Motor starting
 Starting current depend on motor connection
 Why happen motor starting
 In starting motor need more current to run because it need more torque .
 Torque is directly proportional with current
 In running case motor need only save motor rated speed but in starting motor
need to increase speed .

3. Motor starting
 Motor starting types
 Direct on line (DOL)………..I_starting=6*I_normal
 Start –Delta connection …. I_starting=3*I_normal
 Soft starter……………………I_starting=2*I_normal
 With A group of resistance ……its depend on resistance value.
 DOL method:motor is directly connected to the supply I_starting=6*I_normal

4. Manual DOL starter
L2L1
M
3~
M
3~

5. Star-Delta connection

6. Star connection
 In star connection motor work with the highest volt and the lowest current in
nameplate

7. Notes
 Volt star=volt delta *sqrt(3)
 Current star=current delta/sqrt(3)
 Must me connect star or delta connection right to avoid burn motor
 If not found voltage supply as in name plate use transformer to convert supply
voltage to voltage on name plate.
 If we must connect motor as star connection and connect as a delta connection
motor will be burn.
 If we must connect motor as delta connection and connect as a star connection
with the same delta volt motor will be run with half power.

8. Star Delta connection
 In starting connect motor firstly as a Star then convert to delta after reaching to
rated speed .
 KM1 is the main contactor
 KM2 is the star contactor
 KM3 is the Delta contactor

9. Exercises
 Design a control circuit to run motor star then turn into delta without timer just by
pressing start button and operator press another switch to turn into Delta

10. Exercises
 Design a control circuit to run motor star then turn into delta without timer just by
pressing start button and operator press another switch to turn into Delta with
indication lamps

11. Exercises
 Design a control circuit to run motor star then turn into delta with timer

12. Exercises
 Design a control circuit to run motor star then turn into delta with timer

13. Star Delta for motor run in two direction

14. Group of resistance method
 This method is used for induction motor

15. Exercises
 Design a control circuit to run motor with group of resistances

16. Soft starter

17. Overload for motors with high power

18. Example
 Start –stop circuit with current transformer of overload

19. Starting current problem for overload
 Use contactor in parallel with overload to avoid problem and use timer after this
time return to main contactor

20. project

21. Project
 Start button run two conveyors
 When product reach to s1 do the following
 Piston (1A) : Forward until reach to 1S2
 Piston (2A) : Forward until reach to 2S2
 Piston (2A) : Reverse until reach to 2S1
 Piston (1A) : Reverse until reach to 1S1
 Wo conveyor work until new object reach to S1 and do the sequence.

22. project2

23. specification
 Four tanks are discharged manual and filled with four pumps.
 Pumps specification p1=3kw p2=4kw p3=7kw p4=5kw
 Select component with rated current
 Main power max feed=10kw
 Design a control circuit to cover this problem
 You have four switches to indicate high tank level.