Isolation Transformers

Johnson Electric Coil Company
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Three Phase Isolation Transformers

We design dry-type three phase isolation transformers to meet your custom requirements: special voltage requirements, taps where you need them, your choice of winding configurations, terminations to suit your installation, unusual sizes and shapes—up to 250kVA.

Three phase transformer designs are carefully coordinated to meet your critical characteristics: electrical performance, terminations, size, weight, and price.

three phase transformers Wisconsin
The manufacture of three phase isolation transformers for high power and/or high current applications requires sophisticated testing, often using our state-of-the-art multi frequency generator.
single phase transformers Wisconsin

Single Phase Isolation Transformers

We design dry-type single phase isolation transformers to meet your custom requirements: high-reactance, ferro-resonant/constant-voltage, EI, toroid, special voltage requirements, taps where you need them, your choice of winding configurations, paper section or bobbin construction, special brackets, terminations to suit your installation, unusual sizes and
shapes—up to 75kVA.

Why Should You Choose Johnson Coil?

Our goal is to deliver excellent quality products accompanied by top-of-the-line customer service. Whether using the finest techniques to ensure productivity or finding the most cost-effective freight carriers, we got you! We strive for continuous improvement and are earnest regarding our principles and standards.

Our engineers understand environmental compliance concerns and have a comprehensive working knowledge of all applicable market trends. Since 1934, we have been serving various industries. While we mainly sell in the US, our single and three-phase isolation transformers can be found worldwide as components in OEM equipment.

Johnson Electric Coil Company provides complete design, engineering, and manufacturing services to supply our customers with the finest, most efficient and cost-effective single phase and three phase isolation transformers. Our isolation transformer design and manufacturing capabilities are some of the broadest in the industry. We can fully support our customer’s safety agency requirements with expertise in both domestic and foreign agency requirements.

Quality & Service

Our products are all made in Antigo, Wisconsin USA

In addition to our specialty engineering and manufacturing services, we work with our customers to customize scheduling, packaging, shipping, billing, and communication practices to meet their unique inventory management, product handling, delivery, and customer service needs. Our goal is to provide a level of quality and service that enables our customers to be leaders in their markets. While we mainly sell in the US, our single phase isolation transformers and three phase isolation transformers are found all over the world as components in OEM equipment. We pride ourselves on being the only transformer company our customers need.

What are Isolation Transformers?

An isolation transformer is a stationary device with isolated primary and secondary windings that keeps the two circuits separate physically and electrically. It transmits electrical energy between circuits by incorporating the magnetic induction mechanism, which uses a magnetic field to generate EMF in another circuit without affecting the frequency. Isolation transformers are used in transmission and distribution networks to step up and down voltage levels. The voltage and current capacities on both coils of an isolation transformer are equal.

How does an isolation transformer protect you?

One of an isolation transformer’s essential purpose is to eliminate voltage spikes in supply lines. The voltage spikes convey high voltages that can cause service interruptions or damaged equipment if they reach the load. The voltage spikes can be reduced before reaching the load by connecting an isolation transformer between the power supply lines. Another essential feature of an isolation transformer is that it can allow load equipment or the secondary side from being grounded. As a result, load ground loop interference and noise effects are attenuated.

Benefits of Isolation Transformers

Isolation Transformers are extensively used due to the following benefits. They:

  • Can change voltages to match the load needs if different than the source voltage.
  • Protect different kinds of electrical appliances by reducing power surges
  • Block interference caused by ground loops and reduce noise
  • Can reduce earth leakage in equipment used in wet locations
  • Provide stable performance, low energy consumption, and high working efficiency
  • Prevent electronic devices from polluting the power grid

Features of Isolation Transformers

Isolated transformers and normal transformers employ the same working principle, i.e., electromagnetic induction. The transformer illustrated in the image below shows primary and secondary windings with an additional Faraday Shield. The Faraday Shield gives a low impedance path to ground to reduce the coupling of common-mode noise.

Isolation Transformers REV

Applications of Isolation Transformers

Isolation Transformers can generally be used in

  • Critical Power – UPS / Battery Charging / Energy Management
  • Renewables – Wind / Solar / Energy Storage
  • Pulse circuits
  • Medical equipment
  • Devices that are not at ground potential
  • Electronics testing and servicing
  • Computer network configuration
  • Laboratory instruments
  • Motor Drives
  • Radars
  • Grids
  • Telecommunications

How to Choose an Isolation Transformer

When choosing an isolation transformer, one must keep its desired outcome and usage in mind. Based on the applications, one can easily choose the right isolation transformer to meet one’s requirements among the following types:

  • Due to their simple structure and small size, single-phase transformers are suitable for low-voltage distribution networks with small load density. In residential areas, using such transformers is more feasible.
  • Harmonic mitigation transformers are appropriate for installations with many harmonic loads, such as educational institutes, government, commercial, medical, and call-center applications, all of which require the consistent operation of computers, printers, and communication equipment.
  • Drive isolation transformers are used to isolate AC or DC motor circuits from the input voltage system. They can also be employed in industrial heating.
  • K-factor transformers are designed to function in high harmonic loads such as computer rooms and other areas with high levels of non-linear loads.
  • Power generation and electrical distribution network applications both utilize three-phase transformers extensively. They can be found in high-power industrial loads such as rectifiers and motor drives.

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