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04/04/2022

Size of earthing conductor in rotating machines

Earthing connection

  • Each machine is provided with earthing terminal however, the machine shall be neither earthed nor provided earth terminal when
  • They fitted with supplementary insulation
  • They have rated voltage up to 50 V AC or 120 V DC and are intended to do SELV circuit. 
  • If the machine rating greater than 50 V AC or 120 V DC but not exceeding 1000 V AC or 1500 V DC, the terminal for earthing conductor is provided in the terminal box. 
  • If the rating of machine greater than 100 kW or 100 kVA, the earthing terminal shall be provided on the frame.
  • If the rotor winding and bearing of a machine is insulated, the shaft shall be electrically connected with earthing terminal unless the manufacture provided separate protection for it.

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Size of earthing conductor

The size of earthing conductor

  • That of live conductor if the cross-section area of live conductor less than 25 mm2
  • 25 mm2 if the cross-section area of live conductor lies between 25 mm2 and 50 mm2
  • 50% that of live conductor if the cross-section area of live conductor exceeds 50 mm2

Cross section area of earthing conductor


Cross section area of live conductor ( mm2 )

Cross section area of earthing conductor ( mm2 )

4

4

6

6

10

10

16

16

25

25

35

25

50

25

70

35

95

50

120

70

150

70

185

95

240

120

300

150

400

185

 


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