Brief Introduction to Transformers

by | Dec 16, 2014 | Uncategorized

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A transformer is an electrical component used to transfer energy between circuits through electromagnetic induction. A transformer is made up of a core, a primary and a secondary side. The primary side is connected to the input and the secondary side is connected to the load. The primary and secondary are windings of conductive wires around the core. An AC current going through the primary winding creates a varying magnetic flux in the core, which in turn generates a magnetic field that induces a voltage in the secondary winding. The voltage induced on the secondary is proportional to the ratio of the number of turns of wire between the primary and the secondary.

High Frequency Transformers vs. Low Frequency Transformers

Some issues associated with practical transformers include leakage inductance and stray capacitance.  Leakage inductance is caused by poor coupling between windings which leads to amounts of flux “leaking” out and not being transferred to the other winding. The equivalent impedance of the leakage inductance can be modeled using the following equation:

Stray capacitance occurs between windings of a transformer due to their electric fields affecting other windings around them. The equivalent impedance of the stray capacitance can be modeled using the following equation:

It can be seen from the above equations that at high frequencies, the impedance of the leakage inductance increases significantly and the impedance of the stray capacitance decreases significantly and vice versa for low frequencies. At low frequencies (i.e. 60Hz), the impedances of leakage inductance and stray capacitance do not cause major problems. However, at high frequencies, problems such as poor voltage (or current) regulation, oscillation and crosstalk interference may arise due to the very high impedance of the leakage inductance and the very low impedance of the stray capacitance.  These problems can cause unreliable operation or even damage to the transformer and system devices. These high frequency problems can be controlled and even eliminated with proficient transformer designs and manufacturing.

High Frequency Transformer Applications

Some applications that require high frequency transformers include powering piezoelectric components, testing high frequency voltage ripple durability (i.e. motors and capacitors), compliance tests for medical equipment standards (IEC 60601-2, IEC 60601-2-18), generating magnetic fields for wireless power transfer, cardiovascular and sensor technologies etc. Demand for high frequency transformers is relatively low compared to demand for 50 Hz and 60 Hz low frequency transformers. Most of the applications for high frequency transformers are sophisticated industrial testing and research and development oriented projects. Therefore, there are relatively few proficient manufacturers of high frequency transformers for the industrial community.

Amp-Line Corp.

Amp-Line Corp. has a specialty in proficient designing and manufacturing of high frequency transformers for industrial and scientific needs. Amp-Line’s transformers are designed for low leakage inductance and stray capacitance to minimize or eliminate the problems associated with high frequency transformers. Due to the scientific nature of the demand for high frequency transformers, many of Amp-Line’s high frequency transformers are custom made for specific applications. Amp-Line can design and manufacture transformers for high and low voltage applications of up to 1M Hz.


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