I am interested in how you would calculate the voltage drop across a transformer resulting from a motor inrush current due to the transforers impedance using the P.U. method. What if for example I have the following hypothetical setup.
Inside my plant on the secondary of the utility transformer I have a 4.16kV-480V 1500kVA transformer with a 5% impedance. On the secondary of this transformer I have a 300hp motor and assume that this 300hp is equivelent to about 300kVA. Lets assume that the starting current for this motor is 2800A.
I know that I must convert everything to a p.u. impedance. Since I am interested in the VD across the transformer do I simply use .05 as the P.U. impedance or must I covert this to a different kVA base since motor and transformer are two different kVA bases?
Can someone please help me with how I would go about this?
Inside my plant on the secondary of the utility transformer I have a 4.16kV-480V 1500kVA transformer with a 5% impedance. On the secondary of this transformer I have a 300hp motor and assume that this 300hp is equivelent to about 300kVA. Lets assume that the starting current for this motor is 2800A.
I know that I must convert everything to a p.u. impedance. Since I am interested in the VD across the transformer do I simply use .05 as the P.U. impedance or must I covert this to a different kVA base since motor and transformer are two different kVA bases?
Can someone please help me with how I would go about this?