Transformer Calculations - determining turns/current/maximum flux

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SUMMARY

The discussion focuses on calculating key parameters of a single-phase transformer rated at 120 kVA, 2000 V/100 V, and 60 Hz with 1000 primary turns. The secondary number of turns is determined to be 50 turns based on the voltage ratio. The rated primary current is calculated as 60 A, while the secondary current is significantly higher at 1200 A. The maximum flux and the cross-sectional area of the core require further clarification, particularly in relation to the maximum flux density of 0.25 T.

PREREQUISITES
  • Understanding of transformer equations, including voltage and current relationships.
  • Familiarity with electromagnetic principles, specifically flux and flux density.
  • Knowledge of power calculations in electrical systems.
  • Basic grasp of single-phase transformer operation and ratings.
NEXT STEPS
  • Learn about transformer turns ratio and its implications on voltage and current.
  • Study the calculation of maximum flux in transformers using Faraday's law.
  • Explore the relationship between flux density and core area in transformer design.
  • Investigate the implications of high secondary current in transformer applications.
USEFUL FOR

Electrical engineers, students studying power systems, and professionals involved in transformer design and analysis will benefit from this discussion.

Angusbrooks
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The Question
A single phase transformer has the following rating: 120 kVA,
2000 V/100 V, 60 Hz with 1000 primary turns.

Determine:

(A) the secondary number of turns
(B) the rated currents on the primary and secondary
(C) The maximum flux
(D) given a maximum flux density of 0.25 T, the cross sectional area of the core.

Equations used

NP (primary number of turns) VP (primary voltage) IS (Secondary current)
NS (Secondary number of turns) VS (secondary voltage) IP (primary current)

I (current) = P (Power)
V (Voltage)

The attempt at a solution

(A) NP = VP
NS = VS

1000 Turns = 2000V
NS 100V

NS = 100V
2000V

= 0.05V X 1000 Turns

= 50 Turns

(B)i I (current) = P (power)
VP (primary voltage)

I = 120000VA
2000V

= 60 A on the primary

ii I (current) = P (power)
VS (seconday voltage)

I = 120000VA
100V

= 1200 A on the Secondary



(C) I am struggling with this question i understand that I must calculate the maximum flux but am completely lost could someone please advise me in the correct direction?!

(D) as above



Any help would be great thanks!
 
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Part C: Remember emf = -dPHI/dt?
Part D follows immediately.
 

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