Power Transformers

power transformerPower transformers transfer AC electricity from primary to secondary circuits via electromagnetic induction. Depending on their core function, transformers operate for applications ranging from domestic consumption to long-distance transmission with minimal power line loss.

A typical power transformer operates via a system of primary and secondary coils attached to a core. The input and output windings do not require a metallic connection between them to transfer current, helping separate the system’s internal circuitry from the external electrical grid.

Common Power Transformer Designs

Power transformers operate in two main conformations, outlined below:

1-Phase vs. 3-Phase Transformers

power transformerA single-phase transformer uses 1-phase AC, and as such, voltage cycles operating in synchronized time phases power it. Operating with a primary winding and a secondary coil, this equipment steps down voltage into appropriate levels for household and light commercial uses.

One way to create a 3-phase transformer involves integrating three single-phase units. This setup uses three sets of primary and secondary coils. Each unit functions independently, mitigating power interruption when any individual phase breaks down.

Other types of 3-phase transformers use three sets of primary and secondary coils. This relatively inexpensive construction uses less core material than required for a system of three single-phase transformers, making it lighter, smaller, and more energy efficient. Three-phase transformers operate best in high-voltage industrial applications.

Different Transformer Types

Although power transformers operate via the same basic magnetic induction principles, they may differ in size, construction, and power rating depending on commercial, residential, or industrial applications. Different transformer types include:

Types of Power Transformers infographic

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Toroidal Transformers

Toroidal transformers comprise a copper wire tightly wound around a donut-shaped or cylindrical core. Their compact design minimizes magnetic flux leakage, distortion, and interference with sensitive electronic components, making them ideal for use in high-precision medical equipment circuitry.

Additionally, toroidal transformer cores perfectly align with the flux path over the entire electromagnetic field, minimizing core power loss. Low current leakage means greater functional efficiency, allowing for the construction of relatively smaller and lighter transformers.

Depending on the application, toroidal transformers can be configured in laminated, nanocrystalline, ferrite, or power materials.

Flyback Transformers

flyback transformerFlyback transformers originally regulated electron beam motion in television and monitor cathode ray tubes (CRTs). In the flyback structure, the electromagnetic field stores current when the first half of the switching cycle applies voltage to the transformer. After turning the switch off, the output voltage surges sharply in a fraction of a second before dropping in a sawtooth wave.

Nowadays, besides CRT control, flyback transformers have diverse industrial/commercial applications, including switched-mode power supplies. Their circuitry experiences minimal energy loss, making them relatively more efficient. Compared with mains transformers, flyback transformers are lighter and smaller and can function at relatively higher frequencies between 10 and 100 kHz.

EI and EE Laminated Core Transformers

Most power transformers incorporate laminated cores to minimize eddy current induction caused by electromagnetic field fluctuation. This construction optimizes energy transmission from the primary winding to the secondary winding.

In a laminated magnetic core, stacks of thin iron or steel sheets with layers of insulation increase resistance to eddy currents. Restricting the flow of current to small loops within each insulated sheet reduces heating and electrical losses.

EI and EE laminated core transformers normally operate between 50Hz and 400Hz.EI and EE laminated core transformers are also available for audio applications. Transformers for these specific applications utilize nickel in place of the traditional silicon steel material. While the cost of nickel is much higher than silicon steel, it provides higher impedance.

Gate Drive Transformers

Gate drive transformers offer a broad spectrum of benefits. They operate by adjusting the voltage level to the gate using gated semiconductor devices. Gate drive transformers help with voltage isolation and impedance matching applications.

The devices may function as pulse transformers, where they generate voltage pulses to electrically activate or deactivate semiconductors.

Planar Transformers

Aerospace and military applications rely on planar transformers because these devices meet specific technical standards and deliver precise electrical characteristics. Planar transformers’ advantages include:

  • High power density because they function at high switching frequencies
  • Low profile
  • Greater surface area, preventing overheating
  • Large magnetic cross section area, resulting in fewer winding turns and lower copper losses
  • Interleaved windings, reducing leakage inductance

Push–Pull Transformers

Push–pull transformers’ compact construction optimizes their usefulness in switched-mode power supplies. They work best with high-power switching applications between 100 watts to 1,000 watts. In addition to the traditional design type with a center tap input and output, other common design configurations include:

  • Half-bridge configuration: This push–pull transformer has no primary center tap, and it lowers the primary coil capacitance. Two capacitors connected in series reduce the input voltage by half.
  • Full-bridge configuration: This push–pull transformer does not have a primary center tap, and it reduces capacitance in the primary winding. It employs two extra transistors in place of the two series-connected capacitors. For the same voltage supply and power rating, the input voltage to the full bridge circuitry mimics that of a center-tapped, buck-boost transformer.

Switch Mode Power Supply Transformers

Switch mode power supply (SMPS) transformers efficiently step up or step down current or voltage in accordance with power regulation needs, and they also isolate the input and output sides of a power supply from each other. They’re prized for their ability to provide constant output voltages over varying load conditions, and their simple interface offers easy automation capabilities.

SMPS transformers usually work with DC sources to regulate electric flow to one or more output DC sources, and they operate with frequencies ranging from 10 kHz to 1 MHz. Additionally, their small size and flexible design allows a higher power density than other converters, achieving efficiencies of 68–99%.

SMPS transformers benefit the following applications:

  • Computers
  • Cell phones
  • Battery-operated toys or devices
  • GPS transponders
  • Hand-held scanners
  • Equipment
  • Power supply
  • Electrical and electronic appliances

Contact MPS Industries

Are you searching for a highly efficient power transformer for a specific electrical/electronic application? At MPS Industries, we offer different types of such electronic components, from flyback and half bridge to gate drive and planar transformers. Contact us today or request your free quote.

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