Isolation Transformer


A transformer is not a new word for you. You have been told countless times that the transformer close to your hood is the one that pumps electric power, isn’t it? Well, that’s from a layman, today we will be looking at this single device which is very important in the electrical world and specifically isolation transformer. A transformer according to oxford learner’s dictionary is a static electromagnetic device that adjusts the voltage of an electric power supply, usually to allow a particular piece of electrical equipment to be used.

isolation transformer uses for human safety and equipment safety

Construction and operation

It consists of two windings that are primary and secondary. The key characteristic is that the two windings are physically and electrically disconnected but magnetically coupled with the exception of the autotransformer. It’s because of this property that they are called isolation transformers as they electrically isolate circuits while allowing power transmission. To enhance magnetic coupling a laminated iron core is used. The winding is insulated by a thin layer of nonconductor, so thin it looks like a paint.

When an alternating current passes through the primary winding a varying magnetic flux is created according to faradays law of electromagnetic induction. The ratio of primary and secondary windings gives the voltage transformation. This gives three types of transformers;

  • Step down transformer
  • Step-up transformer
  • Isolation transformer that has not voltage transformation

It’s worth noting that the frequency does not change and power output is less of input power only by transformer losses.

Why isolation transformer?

A transformer only designed to offer electrical isolation is termed by this name although many other transformers have isolation as earlier stated. The purpose of isolation is to serve the following functions;

  • Safety- it protects expensive and delicate equipment that usually have microprocessors such as telecommunication device, medical equipment, and computers. By offering physical and electrical isolation, an undesirable power supply such as surges and transients does not get to the load. Faulty equipment in the primary circuit does not affect the secondary side. Farther it prevents undesirable capacitance build up (as it grows with the length of the conductor) by electrically disconnecting.
  • Protect electronic personnel servicing equipment- the technicians are protected from electrical shock from primary circuit fault. Unintentional short circuit on the secondary side does not harm the personnel or equipment. To achieve this the secondary winding neutral and ground are not connected to common ground.  
  • Suppress noise- in telecommunication and measuring instruments such as oscilloscope, it bars dc noise signals and high-frequency unwanted signals from getting to the secondary side safeguarding the equipment. This ensures only the desired signal is available at the secondary side.


The following are some of the areas where isolation transformer is used for purposes of isolation.

  1. Measuring instrument transformers such as oscilloscope, current transformer, and voltage transformer
  2. Medical laboratory equipment is sensitive to unstable power supply and noise
  3. Telecommunication equipment to attenuate dc noise and high-frequency signals
  4. Computers – protect against undesirable power supply such as transients
  5. Special equipment with microprocessors that are sensitive to noise and can be damaged by faults in the power supply.


Electromagnetic induction discovered by Michael Faraday is the science behind the isolation transformer. It truly is an important device to us, its functions are key, and needless to say, it was a timely invention. From medical to telecommunication to instruments it’s a device that sits somewhere in a piece of equipment ensuring its optimal performance.

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