1.)Three identical 1 phase transformers, each rated 500 kva, 4160 - 277 V and60 Hz, connected delta-wye to form 3 phase bank.
Short circuit test measurements taken on HV side of 1 phase transformer

(i.e. LV terminals of 1 phase transformer short circuited together):

Vsc = 250 V, Isc = 120.2 A, Psc = 10 kW.

(a) What is voltage regulation of 3 phase bank if it delivers rated current at rated voltage and 0.9 lagging power factor?

(b) What is the input line current, delta winding current, and wye winding current ifthe load is shorted?

2.)Three identical 1 phase transformers, each rated 25 kva, 34500-277 V and 60 Hz, connected delta-wye to form 3 phase bank.

Open circuit test measurements taken on LV side of 3 phase bank

(i.e. HV terminals of 3 phase transformer open circuited):

Vsc = 480 V (line to line), Ioc = 4.11 A (line current), Psc = 945 W (total 3 phase).

Short circuit test measurements taken on HV side of 3 phase bank

(i.e. LV terminals of 3 phase transformer short circuited together):

Vsc = 2010 V (line to line), Isc = 1.26 A (line current), Psc = 912 W (total 3 phase ).

(a) Find per unit approximate per phase equivalent circuit of 3 phase bank.

(b) Find voltage regulation of 3 phase bank at rated conditions and 0.8 lagging power factor.

(c) What is efficiency of 3 phase bank under conditions of part (b)?

3) 480 volt, 3 phase load of 100 kW (total) at 0.8 lag pf supplied from ideal 2300volt 3 phase source with ideal step-down transformers.

Determine needed kva, voltage, andcurrent ratings of every single phase transformer winding (both primary and secondary) ifthey connected (a) V-V (open delta) and (b) T-T.