Short Curcuit Current

[HienN]

Hi guys,

 

Could you enlighten me on this case?

 

1. If I calculate the SC current in power system and it showed 17kA.

2. What will happen when I choose the MCCB with SC current rated at 10kA if there is SC in the system?

3. What wil happen when I choose the MCCb with SC current rate at 40kA if there is SC in the system?

4. What exactly is the SC current for the MCCB here?

5. Overcurrent protection will do nothing in this SC case?

6. What exactly the SC current on the MCCb's nameplate means?

 

Regards,

[asif]

Hi guys,

 

Could you enlighten me on this case?

 

1. If I calculate the SC current in power system and it showed 17kA.

2. What will happen when I choose the MCCB with SC current rated at 10kA if there is SC in the system?

3. What wil happen when I choose the MCCb with SC current rate at 40kA if there is SC in the system?

4. What exactly is the SC current for the MCCB here?

5. Overcurrent protection will do nothing in this SC case?

6. What exactly the SC current on the MCCb's nameplate means?

 

Regards,

 

Hi HienN,

10kA rating of a MCCB is the maximum short circuit current it can interrupt. If the fault level is more than 10kA, then MCCB won't be able to extinguish the arc fully & there is chance of burnt off contacts & in some cases, explosion due to heat developped inside case. Better you can go for 25kA rating MCCB.

 

If it is 40kA rated MCCB, then there is no problem unless you are not concerned about cost of MCCB. You may still get MCCB of 25kA rating which will be less costly than 40kA.

 

The basic difference between OC & SC operation is time factor. Short time delay & Long time delay are different for both operations.

 

Short circuit current on the MCCB's name plate is the capacity of MCCB to interrupt a fault of that level safely.

 

Thanks & Regards,

Asif Mansoori

Mumbai