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We understand there is a EMC filter switch in ATV31 range( up to 7.5Hp), and it can be lifted if its power is a I.T. system. 1. Actually, we was tol...

Goals and Symptoms

We understand there is a EMC filter switch in ATV31 range( up to 7.5Hp), and it can be lifted if its power is a I.T. system.
1. Actually, we was told there is a very few power system using I.T. system. Could you please give us examples what condition and what EQUIPMENT must use I.T. system? Is there any country use this I.T. system?
2. What would be problem if this EMC filter switch not disconnected in I.T.system?

Causes and Fixes

The current of first insulating defect is limited, by the impedance connection with the ground of the point medium of the transformer (2000 ohms), and with a value such that does not result from dangerous voltage of contact. i=230V/2000 ohms = 100mA (simplified equation) protection does not require a cut, which makes it possible to maintain the continuity of service. With the second insulation defect , the automatic cut must intervene. The defect phase/ground degenerates into short-circuit equivalent to a defect phase/phase. The device safety against the courts - circuits (circuit breaker) thus it will locate and cancel it instantaneously. Protection against the indirect contacts is ensured by the circuit breakers with rate IT. The differentials are useless (N.B.: the pole of neutral must also be protected).

This neutral mode is used for continuity service, use in a lot of countries ( France for example ).

EMC filter capacitors could be damaged because of an overvoltage in case of contact between one input phase suplly and the earth.
Other reason:
The leakage currents generated cause a dysfunction of the insulation fault detection devices (Permanent Insulation Monitor (PIM) or Residual Current Device (RCD)

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