Isolation Transformers: Why Are They Used?

An isolation transformer is the most basic type of transformer in industrial machinery, in which primary and secondary windings are separated. Alternatively known as insulated or linear transformers, these fundamental devices are designed to complete multiple tasks.

Here are some of the uses and benefits of these essential components in high end electrical equipment.

Voltage Control The reason an isolation transformer has primary and secondary windings is to either step-up or step-down the voltage output, generating electrical isolation between the windings. One of the most important aspects of this process is that electrical noise between the windings is reduced. These transformers are designed to provide either one phase (AC) or three phase (AC, transmission, distribution) electrical power.

Impedance Matching Within the transformer, one side of low voltage is connected with another side of higher voltage. The low voltage side has low impedance while the opposite side converted to high voltage has high impedance due to more coil turns. The isolation transformer can generate superior impedance matching of a critical load to an electrical circuit. An internal low impedance isolation transformer, on the other hand, creates complete isolation from the input AC line.

Common Uses and Benefits

• Sensitive electronic hospital equipment that prevents shock
• Protect various electronic equipment for telecom, transactions, diagnostic testing
• Continuous filtering of power line noise, producing an isolated neutral-ground reference
• Reduction of electrical surges, which protects equipment
• Removal of neutral-to-ground voltage and noise, improving reliability
• Provide safe conditions in electronic testing, troubleshooting and servicing
• Cut costs vs. dedicated circuits and site electrical upgrades

How to Increase Isolation Adding electrostatic shielding increases isolation between the primary and secondary windings. Faraday shields enhance power quality by attenuating higher frequency noise currents. They also reduce the cumulative leakage current of the isolator and the connected equipment by less than 300 micro amps.

A grounded shield between the transformer windings may cut down the coupling of common-mode noise in supply conductors. Isolation transformers are designed with a filter circuit to block differential noise from the secondary winding.