# Mathcad - 05-05 - Three-phase transformer bank rated...

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So choose at least a 20 KVA transformer for each phase. In reality we wouldn't want to load the transformer to 100% of it's rating so probably a 25 KVA transformer would be better. S delta 19.777kW = S delta S in 3 = c. For operation in closed delta, each transformer supplies one-third of the Volt-Amps I line 77.853 amp = I line S in 3 V s = S in 59.332 KVA = S in P in F p = P in 48.652kW = P in P out eff = P out 44.76kW = P out HP 746 watt hp = F p 0.82 = HP 60 hp = eff 0.92 = V s 440 volt = Given: KV kV b. Find the motor line current: KVA kW primary secondary A B C A B C motor 2400 V 440 V III III I I II II Problem 5-5 Solution:

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Unformatted text preview: Three-phase transformer bank rated 2400-440. Motor is 60 HP operating at rated power, 440 v, and 0.82 lagging power factor with efficiency of 0.92 a. Draw and label the system: d. For open delta or "V" operation, each transformer is rated to supply the total three-phase load over the square root of three: S phase I line V s ⋅ = S V S in 3 = or S V 34.255KVA = S phase 34.255KVA = So we would probably have to choose at least a 37.5 KVA transformer for each phase...
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## This note was uploaded on 03/26/2012 for the course ECET 231 taught by Professor Piller during the Spring '12 term at Purdue.

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Mathcad - 05-05 - Three-phase transformer bank rated...

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