DOL and distribution transformers utilization

[usamaegypt]

Dear all,
We have a distribution transformer with the following data:
6300/400 V , nominal current on LV side 2886 A , short circuit impedance is 6.34%. The actual consumption for this transformer is 1616 A. We want to add a load of 700 A to this transformer to feed T/R set for ESP filter. This load will be 2 phases , 380 V. We have also a motor 160 KW , 280 A , DOL connected to the same transformer and we are worry from the effect of voltage drop that might happned after adding the new loads 700 A , during the direct on line start of the 160KW motor.
We are looking forward for your advise.
Best regards.

 

[ScottyUK]

On a 2MVA transformer and assuming that the upstream network is reasonably solid I don't think you will have a problem with both loads on this transformer. You will see a sag in voltage when the motor starts, and you should check how well the T/R unit will deal with this.

Estimating the voltage sag requires more information than you've provided because the upstream network impedance and motor starting method will influence the depth of the sag, and the acceleration characteristics of the motor load will affect its duration.



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