Isolation transformer

1:1 isolation transformer

What is isolation transformer?
How it works?
What happens when the secondary of a isolation transformer is shorted?

isolation transformer in bathroom

isolation transformer is just an ordinary transformer... the name is because it is used for the purpose of isolation... i.e. the source connected to primary is very high voltage compared to secondaries output or the source is prone to noise and glitch.....

shaver point isolation transformer

An isolation transformer provides an electrical isolation or barrier between a high potential and a low potential. You will see these used to step down wall power AC to a lower voltage in many commercial devices. These are typically used as a safety device.

How does it work? The voltage is stepped down in proportion to the ratio of the windings for the secondary side to the primary side.

I take it your question about shorting the secondary side of the transformer is meant to ask what happens if I short the secondary to ground. If you short it this way all the power on the primary should be shunted to the ground or neutral line and leave the circuit. HOWEVER if the transformer starts to degrade that primary line potential could break through the short and possible swarm into the rest of the circuit.

E

isolating transformers in the bathroom

An isolation transformer does not generally change the voltage. It is used to isolate mains a.c. voltages from ground. A typical application is before a shaver socket in a bathroom. So that if you happen to get a problem of the appliance (shaver) going live you cannot get electrocution problems if you touch the many sources of ground in a bathroom.

microwave oven transformer smaw

Quibbler it does NOT isolate from AC main to ground, it isolates from high potential to low potential (i. e. the neutral line) and it is required to drop the potential (voltage and current) on the secondary side when used in a commercial product application.

When is the last time you saw a 1:1 transformer used for any product that a person would be holding such as an electric razor?

That answer is you have not. You will never see a 1:1 transformer in a product like that. Why? Because the potential to kill someone is great. That is why all products powered off of a wall socket are required by every safety agency to use a step down isolation transformer as a minimum.

And in case you dont know, the earth ground that you are referring to is not found in the wall socket. That is found at the circuit breaker.

isolation transformer measurement

Most of the transformers in wall adapters (which stepdown 110/220VAC to 1.5 or 3, 4, 6, 9, 12, 15, 24V) are ISOLATION transformers, where the primary and secondary windings are isolated from each other.

Most of the transformers that are used for the purpose of mains voltage regulations such as 220V:110V stepdown, AC voltage regulators are NON ISOLATION transformers, where secondary winding is a part of primary winding.

However, when people talks about the ISOLATION transformers, they mention about the 1:1 transformer with seperate identical primary and secondary windings. They supply the mains voltage at secondary winding. This kind of transformer is used for safety purpose.

You may know that mains lines in our houses have the L (line) terminal and the N (neutral) one. The N terminal is grounded at the power transformer station. That is why when you touch the neon bulb electric tester tip to the L terminal, the neon bulb lights, and to the N terminal, the neon bulb does not light. And when you stand on ground but touch the L terminal, you must be electrically shocked.

The isolation transformer now supplies the mains voltage, but not any of its terminal is grounded, so it is safe for you when touching to one of its terminals.

Of course, the transformer must be blown when you shorten the secondary termicals if there is not any suitable fuse or circuit breaker at primary and secondary sides. You must use suitable fuses or circuit breakers at both sides of the isolation transformer, or at least the primary side.

nguyennam

1 1 transformer

Hi nxtech

I would just like you to note that your statements in your post makes it sound like there is no place for 1:1 isolation transformers in consumer/handheld electronic devices. I can think of one used usually outside of the bathroom, i.e. an oscilloscope. Sometimes you need an isolation transformer to allow measurements when mains powered equipment are at different ground potentials.

CVT

oscilloscope isolation transformer safety

1:1 isolation transformers are used. It allows whichever point of the circuit is accidentally or deliberately touched to be referenced to the potential of the touching conductive body without causing current to flow (other than equalization charge). On the other hand if two points on the circuit are connected, they become part of that circuit.

isolation transformer electronic fuse

it is normal there is somehow confusion about that. When isolation transformer is explicitly said, that means it is really for HV separation purposes between primary and secondary. It is usually benefited in test/measurement applications, where primary side is higher voltage than secondary (protection for electronic parts/components and en user/network). And yes, it is true, very often windings are 1:1.

However, in other applications like household/bathroom, you have a step-down transformer, which has also ability for isolating primary and secondary voltages. In the end windings are separate and there is no galvanic touch in between themselves and them&core. So primary and secondary are really galvanically isolated. So sometimes these transformer are also interpreted/named as isolation transformer. It is not completely wrong, in the sense of application feature. However, the very usage of this name in literature/industry is still for applications mentioned first (test etc.).

There are also transformers, which dont have any isolation. For example, when secondary winding is part of primary one, there is no isolation between windings. I guess auto transformers are such kind.


You can find some info simply in wiki.
https://en.wikipedia.org/wiki/Isolation_transformer

Hope helps to some degree.

household step down transformers perth

I think an isolation transformer is always for safety.
I have one in my garage made with two old microwave oven transformers.

need for isolation transformer

I guess one of the simplest way (not sure if better than single fully shielded transformer) to make it is to connect two same transformers back-to-back (might be the case of Brumi).

Outlet/Wall Plug ---> [Primary::Secondary--> Secondary:rimary]--> Isolated Output

220-110v transformer galvanic separation

Most transformers provide isolation from supply. Exceptions as noted in the autotransformer. Transformers of course can be step up or down.

Grounding is done by code at the supply transformer, and for our homes, that can be done locally(as close as the transformer hanging on the pole at the back yard). The second ground is made at your home's entrance service. Subsequent transformers must be grounded, as they become a source.

In regards to the shorted current; the transformer secondary will supply a short circuit current that is it's VA current divided by the % impedence of the transformer. A transformer rated at 10 amps with a 5% impedence will supply a short circuit current of 200 amps. The percent impedence is not always available, but it is the percent of voltage / over rated voltage of the primary that will cause the rated secondary current to flow, when the secondary is shorted.

'Isolation' transformers are typically used in instrumentation to reduce an unmanagable quantity to a measurable quantity

Brumi - Isolation xfmrs are also very useful for eliminating ground loops. Not just limited to safety applications.

On of the purpose of isolation transform is to prevent ground loops and isolate effects of lightning strikes.

We are using 1:1.1 isolation transformer for providing supply to instrumentation systems.

There are 1:1 or 2:1 isolation transformers whare the secondary is centre tapped
and the CT is held to earth. In this case there are two live wires but only half the voltage will flow to earth should the sort of malfunction occur whare the case is shorted to live. Use of power tools outside for instance