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What are the points to check SCF3 fault on ATV71 drive; the application is submersible pump.

The purpose of this SCF3 i.e.Ground short circuit is to detect a short circuit to the ground at the start-up or during the running.Quick hardware detection with a current transformer around the three incoming power leads for the smaller ranges and the 3 separate current transformers for the big ranges.
Probable causes:--
* High leakage current to ground on the output of the drive when connecting motors in parallel.
* Long shielded cables
* Bad motor isolation

Remedies:--
• Check the cables connecting the drive to the motor, and the motor insulation.
• Reduce the switching frequency.
• Connect chokes in series with the motor.
• Perform the IGBT diagnostic tests via the [1.10 DIAGNOSTICS] menu.
 
With this kind of application (i.e. submersible pumps), the earth leakage current is increased because of the submerged motor cable. In fact, the earth capacitor of motor cable becomes higher and higher because of the part cable in the water. It is because of the earth capacitor of motor cable that the drive trips in SCF fault.
 
However, following are the general recommendation for this application: --
1. Insulation level of motor should be F class.
2. Do not use shielded cable.
3. Select Motor Choke/Sinus Filter depending on the Submersible motor cable length.

Note:--
Reduce the earth leakage current of the motor cable:--
• use an inductance or filter between the drive and the motor to reduce the dV/dt . Sinus Filter is the better option for this application.
• don’t use shielded cable if there is no EMC requirement
• reduce the switching frequency
• if possible then reduce the wire length between the drive and the motor
 

 
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