Why do we use AC power isolation transformer?

The purpose of an AC isolation transformer, which invariably has symmetrical windings, is to decouple two circuits. The well-known fact is an isolation transformer allows an AC signal or power to be taken from one device and fed into another without electrically connecting the two circuits. Isolation transformers are deployed to block transmission of DC signals from one circuit to the other, but allow AC signals to pass. Isolation transformers with electrostatic shields are used for power supplies for highly sensitive equipments such as computers or laboratory and other precision instruments.

Some of the branded high quality isolation transformers include brand names such as GE Industrial Transformer, TEMCo Transformer, Marcus Transformer, Federal Pacific Transformer, and Acme Transformer with capacities ranges from 0.05 kva to 5000 kva. AC power isolation transformers are perfect for operating sensitive equipments that can not tolerate today's higher line voltages (ie.125 VAC input will produce a stress free 105 VAC output at full load + isolation and shielding). The general features of AC isolation transformers are; ventilated black steel case, rocker lighted on-off switch and fuse protected output. These high quality AC isolation transformers units are also designed for maximum versatility.

Ac power isolation transformerThere are also shielded isolation transformers that have all the features of the standard isolation transformers plus they have a full metallic shielding - of either copper or aluminum - between the primary and secondary windings. These shielded isolation transformers are referred to as electro-statically shielded isolation transformers. The electrostatic shield also called "Faraday Shield" is connected to earth ground to filter (attenuate) voltage spikes (voltage transients). These shielded isolation transformers have an attenuation ratio of 100 to 1. It also filters common mode noise. This is usually an attenuation of approximately 30 decibels.

Traditional filters will only filter out noise on the hot line. Yet noise on the neutral line can also cause problems. The Isolation AC Power Supply will effectively filter both the hot and neutral lines. Isolation AC Power Supply unit will isolate an amplifier from the source components. If you have ground loop problems, where there are multiple electrical paths for ground, this unit will electrically isolate the amplifier or the offending component.

Shielded AC Isolation Transformers are preferred over standard isolation transformers because they provide protection for sensitive and critical equipment. Most all of the general purpose isolation transformers 250 VA and larger are shielded at no added cost as a standard feature.

AC isolation transformers are commonly designed meticulously to capactivate coupling between the two windings. This is essential because excessive capacitance could also couple AC current from the primary to the secondary. A grounded shield is commonly interposed between the primary and the secondary. Any remaining capacitive coupling between the secondary and ground simply causes the secondary to become balanced about the ground potential.

In electronics testing, troubleshooting and servicing, an isolation transformer is a 1:1 power transformer which is used as a safety precaution. Since the neutral wire of an outlet is directly connected to ground, grounded objects near the desk, lamp, concrete floor, oscilloscope ground lead, etc. may be at a hazardous potential difference with respect to that device. By using an isolation transformer, the bonding is eliminated, and the shock hazard is entirely contained within the device.