The voltage applied to a transformer primary is increased keeping V/f constant. With this, the core loss ____ and the magnetizing current (Im) ____

• A. increases, increases
• B. decreases, increases
• C. remains constant, decreases
• D. increases, remains constant

Answer: (D)

For trasnformer:
1. e = 4.44fφ*Turns
2. V/f ≈ e/f ∝ φ ∝ B
3. Eddy Current loss, Pe ∝ B²f² ∝ f² (as B is constant if V/f is constant)
4. Hysteresis loss, Ph ∝ B^1.6*f ∝ f
If V/f is constant, B is constant, mmf required to create B is constant, Im is constant.