Transformer Types & Applications

Transformers: Types and Applications

What are Transformers?

• Electrical devices that convert AC voltage levels (high to low or low to high) using electromagnetic induction.
• Input and output are AC.

Transformer Components

• Primary Coil/Winding: Input side wire wrapped around the core.
• Secondary Coil/Winding: Output side wire wrapped around the core.
• Core: Ferromagnetic material (e.g., iron) that conducts a magnetic field.

Transformer Operation

• Utilizes mutual inductance to induce AC voltage in the secondary coil from AC current in the primary coil.
• Core concentrates the magnetic field, improving energy transfer efficiency.

Mutual Inductance

• AC current in one coil induces AC voltage in a nearby coil due to the magnetic field.

Turns Ratio (TR)

• Ratio of the number of turns in the primary coil Np to the number of turns in the secondary coil Ns.
• TR = \frac{Np}{Ns}

Transformer Output Voltage Formula

• Vs = \frac{Vp}{TR}, where:
  • V_s = secondary voltage (Volts)
  • V_p = primary voltage (Volts)
  • TR = turns ratio

Formulas

• TR = \frac{Vp}{Vs}
• TR = \frac{Np}{Ns}
• \frac{Vp}{Vs} = \frac{Np}{Ns} = \frac{Is}{Ip}

Input and Output Power

• Ideally, input power equals output power, but in practice, power loss occurs:
• P{in} = P{out} + P_{loss}

Transformer Efficiency

• Power loss is converted to heat; efficiency can be calculated.

Transformer Types

• Isolation Transformer
• Autotransformer
• Control Transformer

Isolation Transformer

• Primary and secondary are physically isolated (no electrical connection).

Advantages

• Reduces or eliminates voltage spikes in the secondary.
• Protects secondary load from primary shorts.

Autotransformers

• Uses a single coil for both primary and secondary.
• Taps on the coil provide different voltage ratios.

Control Transformer

• Reduces main power line voltage to a lower voltage for machine control systems.
• Common type has two primary coils (H1H2 and H3H4) and one secondary coil (X1X2).