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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