A 20kVa, 50Hz, 1100v/240v, single-phase transformer has a gross cross-sectional area of 0,008m². Determine the number of primary and secondary turns if the maximum flux density is 1,5Wb/m². Take the stacking factor to be 0,93.

User Icon for Bot GPT 4-o mini Bot GPT 4-o mini answered
18 days ago

To determine the number of primary and secondary turns of the transformer, we will use the transformer equations and the given parameters.

Step 1: Calculate the Maximum Magnetic Flux (Φ)

The formula for the maximum magnetic flux (Φ) is:

\[ Φ = B_{max} \cdot A \]

Where:

  • \( B_{max} \) is the maximum flux density (1.5 Wb/m²)
  • \( A \) is the cross-sectional area of the core (0.008 m²)

Substituting the values:

\[ Φ = 1.5 , \text{Wb/m²} \cdot 0.008 , \text{m²} = 0.012 , \text{Wb} \]

Step 2: Calculate the Effective (True) Flux (Φ_eff)

The effective flux can be calculated as:

\[ Φ_{eff} = Φ \cdot \text{stacking factor} \]

Substituting the stacking factor of 0.93:

\[ Φ_{eff} = 0.012 , \text{Wb} \cdot 0.93 \approx 0.01116 , \text{Wb} \]

Step 3: Calculate the Number of Turns

The number of turns (N) is related to the voltage, frequency, and effective flux as follows:

\[ N = \frac{V}{4.44 \cdot f \cdot Φ_{eff}} \]

Where:

  • \( V \) is the voltage (in this case, we will calculate both primary and secondary voltages)
  • \( f \) is the frequency (50 Hz)
  • \( Φ_{eff} \) is the effective flux (0.01116 Wb)

For Primary Turns:

Given:

  • Primary Voltage \( V_p = 1100 , \text{V} \)

Calculating the number of primary turns:

\[ N_p = \frac{1100}{4.44 \cdot 50 \cdot 0.01116} \]

Calculating the denominator:

\[ 4.44 \cdot 50 \approx 222 \] \[ 222 \cdot 0.01116 \approx 2.48 \]

Now substituting back:

\[ N_p \approx \frac{1100}{2.48} \approx 442.74 \approx 443 \text{ turns} \]

For Secondary Turns:

Given:

  • Secondary Voltage \( V_s = 240 , \text{V} \)

Calculating the number of secondary turns:

\[ N_s = \frac{240}{4.44 \cdot 50 \cdot 0.01116} \]

Using the previous calculation for the denominator:

\[ N_s \approx \frac{240}{2.48} \approx 96.77 \approx 97 \text{ turns} \]

Conclusion:

The number of turns for the transformer is approximately:

  • Primary Turns (N_p): 443 turns
  • Secondary Turns (N_s): 97 turns