Over Load Relay & Contactor for Starter

Over Load Relay & Contactor for Motor Starter:

Types of Over Load Relay:

  1. Class 10: Would Trip after 10 seconds.
  2. Class 20: Would Trip after 20 seconds.
  3. Class 30: Would Trip after 30 seconds.
  • Over Load Relay should be set 115% to 130% of Motor Full Load Current.
  • Class 10 is faster than Class 20 and Class 30 over Load Relay.

Size of over Load Relay:

Size

Amp Capacity

S00

0.1 To 0.4

0.4 To 0.6

1.6 To 6

3 To 12

S0

3 To 12

6 To 25

S2

6 To 25

13 To 50

S3

13 To 50

25 To 100

S6

50 To 200

S10 & S12

55 To 250

200 To 540

300 To 63

Contactor Coil:

Coil Voltage (40 To 50 Hz) Suffix
24V T
48V W
110V To 127V A
220V To 240V B
277V H
380V To 415V L

Type of Contactor for Starter:

Contactor

Application

AC1

Non-Inductive or Slightly Inductive ,Resistive Load

AC2

Slip Ring Motor

AC3

Squirrel Cage Motor

AC4

Rapid Start / Stop

AC5a

Switching of Electrical Discharge Lamp

AC5b

Switching of Electrical Incandescent Lamp

AC6a

Switching of Transformer

AC6b

Switching of Capacitor Bank

AC7a

Slightly Inductive Load in Household or same type load

AC7b

Motor Load in Household Application

AC8a

Hermetic refrigerant Compressor Motor with Manual O/L Reset

AC8b

Hermetic refrigerant Compressor Motor with Auto O/L Reset

AC12

Control of Restive Load and Solid State Load with optocoupler Isolation

AC13

Control of Restive Load and Solid State with T/C Isolation

AC14

Control of Small Electro Magnetic Load ( <72VA)

AC15

Control of Small Electro Magnetic Load ( >72VA)

 Making and Breaking Capacity of Contactor:

Contactor Making Capacity(Amp) Breaking Capacity (Amp)
AC1 1.5 X motor rated current 1.5 X motor rated current
AC2 4 X motor rated current 4 X motor rated current
AC3 10 X motor rated current 8 X motor rated current
AC4 12 X motor rated current 10 X motor rated current
AC5a 3 X motor rated current 3 X motor rated current
AC5b 1.5 X motor rated current 1.5 X motor rated current
AC6a 12 X motor rated current 10 X motor rated current
AC6b 12 X motor rated current 10 X motor rated current
AC7a 1.5 X motor rated current 1.5 X motor rated current
AC7b 8 X motor rated current 8 X motor rated current
AC8a 6 X motor rated current 6 X motor rated current
AC8b 6 X motor rated current 6 X motor rated current
AC12    
AC13 10 X motor rated current 1.1 X motor rated current
AC14 6 X motor rated current 6 X motor rated current
AC15 10 X motor rated current 10 X motor rated current

 Contactor Status:

Contactor Status Continuity Between  Pins (N/C) Non Continuity Between Pins (N/O)

Power Not Applied

32 and 33

21 and 22

11 and 12

A1 and A2

B1 and B2

Power Applied

21 and 22

32 and 33

11 and 12

A1 and A2

B1 and B2

 Main Circuit Voltage of O/L Relay & Contactor:

  1. A.C= 240V,415V
  2. D.C=230V,460V,600V

Contactor’s Coil Voltage:

  1. A.C= 40V,220V,240V,415V
  2. D.C=24V(For PLC),110V,230V,460V

Rated Current of Contactor: (Thermal and Intermediate Duty):

  1. A.C= 6,10,16,25,63,100,160,200,315,400,630,800 Amp
  2. D.C= 16,20,80,160,315,1250,8000 Amp.

Contactor / Relay Setting / Fuse / Cable for DOL STARTER

H.P

KW

FLC

Contactor Size (Amp)

Relay setting

Fuse

Cable (mm2)

Min

Max

Cu

Allu

0.5

0.37

1

0.8

1.17

4

1

1.5

0.75

0.55

1.3

9

1

1.5

4

1

1.5

1

0.74

1.9

9

1.6

2.3

6

1.5

2.5

1.5

1.11

2.6

9

2

3

6

1.5

2.5

2

1.49

3.7

9

2.5

3.7

10

1.5

2.5

3

2.2

4.8

9

4

5.9

16

1.5

2.5

5

3.73

7.8

9

6.3

9.4

20

1.5

2.5

7

5.22

11.2

12

8

11.7

25

2.5

4

10

7.46

16

16

12.5

18.7

25

4

6

12.5

9.32

19

32

16

23.4

32

4

6

15

11.19

20.8

32

16

23.4

50

6

10

20

14.92

28

32

20

30

50

6

10

25

18.65

34

38

32

37.4

63

10

16

30

22.38

40

45

32

47

80

16

25

40

29.84

53

63

50

59

100

25

35

50

37.3

65

70

57

65.5

125

25

50

60

44.76

78

85

70

88.9

125

25

50

75

55.95

96

110

85

98.2

160

50

70

100

74.6

131

140

115

168

200

70

95

125

93.25

156

170

115

168

250

120

150

150

111.9

189

205

160

234

315

150

240

180

134.28

227

250

160

234

355

185

300

215

160.39

271

300

200

299

400

270

201.42

339

400

250

374

500

335

249.91

338

475

320

468

500

Relay Range & Back up Fuse for DOL Starter

H.P

KW

Full Load Current (amp)

Relay Rang(Amp)

Back Up Fuse

Min

Max

10

7.5

13.6

13 To 20

25

50

12.5

9.3

17

13 To 20

25

50

15

11.2

20

20 To 30

35

80

20

14.9

28

20 To 30

60

80

25

18.7

35

30 To 45

60

100

30

22.4

40

30 To 45

80

100

35

26.1

47

45 To 63

80

125

Relay Range & Back up Fuse for Star / Delta Starter

H.P

KW

Full Load Current (amp)

Relay Rang(Amp)

Back Up Fuse

Min

Max

20

14.9

28

13 To 20

60

60

25

18.7

35

20 To 30

60

100

30

22.4

40

20 To 30

60

100

35

26.1

47

20 To 30

80

100

40

29.8

55

30 To 35

80

125

50

37.3

66

30 To 35

100

125

60

44.8

80

45 To 63

100

160

75

55.95

95

45 To 63

125

160

About Jignesh.Parmar
Jignesh Parmar has completed M.Tech (Power System Control), B.E(Electrical) from Gujarat University. He has more than 13 years experience in Power Transmission-Power Distribution-Electrical energy theft detection-Electrical Maintenance-Electrical Projects(Planning-Designing-coordination-Execution). He is Presently associate with one of the leading business group as a Deputy Manager at Ahmedabad,India. He is Freelancer Programmer of Advance Excel and design useful Excel Sheets of Electrical Engineering as per IS,NEC,IEC,IEEE codes. He is technical Author for "Electrical Mirror" and "Electrical India" Magazines. He is Technical Blogger and Familiar with English, Hindi, Gujarati, French languages. He wants to Share his experience & knowledge and help technical enthusiasts to find suitable solutions and updating themselves on various Engineering Topics.

10 Responses to Over Load Relay & Contactor for Starter

  1. Hament Kaushik says:

    thanks sir ji
    tis is very usfull for us.

  2. Saahib Ghouse says:

    Please provide relay coordination examples ..hand calculations if included and developing curves, selection of relay curves.
    Thumb rules or any logic or technic or any hidden knowledge in performing relay coordination studies and settings.

    Thanks for your knowledge sharing…you are a real master..

    Best Regards,

  3. nikhil says:

    sir please insist me the contactor size for the star delta stater also…….. and simple hand cluculations….

  4. TANVEER SHAH says:

    definitely your sharing valueable knowledge is a great task remembered to be ever for comforting other keep it up good job good contribution wish u more grow to show such a contributon to deliver spreading valueable knowledge.

    thanks

    TANVEER SHAH

  5. rishabh says:

    thank you for posting it but it is incomplete knowledge for an engineer . he also deserves to know about various specifications as what is voltage and power factor that you have taken into consideration for making this chart. . please provide some basics so that i can select mccb, contactor . o\l relay. for dol and s\d starter.
    kindly provide some information.

    THANKS

  6. MUHAMMAD AFROOQ JAMAL says:

    really great and very helpfull…

  7. Yatindra says:

    To calculate size of fuse, contactor, relay,cable of motor please help us.

  8. arjun says:

    Dear Sir,
    Your electrical basic note are very valuable as compare to diamond these notes cover all data which are very important for gaining knowledge of career growing engineers. please help me for understanding how 11kv transmission line enter in the plant , how its connected to the LT panel please help me.

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