science

Isolation transformer

Isolation transformer is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Isolation transformer rather than just read about it. In short: An isolation transformer is a transformer used to transfer electrical power from a source of alternating current (AC) to some equipment or device while isolating the powered device from the power source, usually for safety reasons or to reduce transients and harmonics. Isolation transformers provide galvanic isolation; no conductive path is present between source and load.

Key takeaways

Isolation transformer belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Isolation transformer to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Isolation transformer from memory before moving on to harder problems.

Reference excerpt

An isolation transformer is a transformer used to transfer electrical power from a source of alternating current (AC) to some equipment or device while isolating the powered device from the power source, usually for safety reasons or to reduce transients and harmonics. Isolation transformers provide galvanic isolation; no conductive path is present between source and load. This isolation is used to protect against electric shock, to suppress electrical noise in sensitive devices, or to transfer power between two circuits which must not be connected. A transformer sold for isolation is often built with special insulation between primary and secondary windings, and is specified to withstand a high voltage between windings. Isolation transformers block transmission of the DC component in signals from one circuit to the other, but allow AC components in signals to pass. Transformers that have a ratio of 1 to 1 between the primary and secondary windings are often used to protect secondary circuits and individuals from electrical shocks between energized conductors and earth ground. Suitably designed isolation transformers block interference caused by ground loops. Isolation transformers with electrostatic shields are used for power supplies for sensitive equipment such as computers, medical devices, or laboratory instruments. Some specifications require that Isolation transformers be a part of the lightning protection on the AC circuits.

Terminology Sometimes the term is used to emphasize that a device is not an autotransformer whose primary and secondary circuits are connected. Power transformers with specified insulation between primary and secondary are not usually described only as "isolation transformers" unless this is their primary function. Only transformers whose primary purpose is to isolate circuits are routinely described as isolation transformers.

Operation Isolation transformers are designed with attention to capacitive coupling between the two windings. The capacitance between primary and secondary windings would also couple AC current from the primary to the secondary. A grounded Faraday shield between the primary and the secondary greatly reduces the coupling of common-mode noise. This may be another winding or a metal strip surrounding a winding. Differential noise can magnetically couple from the primary to the secondary of an isolation transformer, and must be filtered out if a problem occurs.

Applications

Pulse transformers

Some small transformers are used for isolation in pulse circuits.

Electronics testing In electronics testing and servicing, an isolation transformer is a 1:1 (under load) power transformer used for safety. Without it, exposed live metal in a device under test is at a hazardous voltage relative to grounded objects such as a heating radiator or oscilloscope ground lead (a particular hazard with some old vacuum-tube equipment with live chassis). With the transformer, as there is no conductive connection between transformer secondary and primary, only a small leakage current will flow if the exposed live metal is connected to earth. Even if an isolation transformer is used, hazardous voltages may still be present between components of the isolated device. Thus it is still possible for an operator to be exposed to lethal voltages by touching multiple elements in the circuit. An isolation transformer provides maximum protection when the device is ungrounded. Connecting it to test equipment, for example, an oscilloscope or a benchtop multimeter, may ground the circuit. Electrical isolation is considered to be particularly important on medical equipment, and special standards apply. Often the system must additionally be designed so that fault conditions do not interrupt power, but generate a warning.

Supply of equipment at elevated potentials Isolation transformers are also used for the power supply of devices not at ground potential. An example is the Austin transformer for the power supply of air-traffic obstacle warning lamps on radio antenna masts. Without the isolation transformer, the lighting circuits on the mast would conduct radio-frequency energy to ground through the power supply.

See also Balun Power quality Transformer types Zigzag transformer

References

External links Transformer Isolation

Illustrations

Worked examples

Example 1 — a first encounter with Isolation transformer

Start with the simplest possible case. Write down what Isolation transformer claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Isolation transformer before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Isolation transformer ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Isolation transformer

In research: Isolation transformer appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Isolation transformer in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Isolation transformer is common in secondary-school and first-year university syllabi. It links to neighbouring topics Electric power conversion, Electric transformers, Electrical safety, so understanding it makes those chapters shorter.
In everyday life: Look for Isolation transformer outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Isolation transformer in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Isolation transformer means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Isolation transformer out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Isolation transformer in simple terms?

Why does Isolation transformer matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Isolation transformer?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Isolation transformer.