Ascend Electronics® has designed and manufactured a variety of Ferroresonant Power Transformers and Power Supplies for applications in automatic controls, industrial machines, computers, aerospace, marine electronics, biomedical equipment, geophysical instrumentation, military applications, oilfield service, audio applications, and more.
Typicaly Applications of ferroresonant power supplies
This supply type is used on applications requiring continuous power and isolation from mains disturbances. These include:
- High-Reliability Power Supplies
- Lightning Systems
- Inverter & UPS Systems
- Battery Chargers
- Line Voltage Stabilizers
- Cable television, gas, and other heavy industries
The ferroresonant power supply systems provide reliable regulation even under extreme operating conditions and are unaffected by surrounding electrical systems. The resonant regulators provide a constant average output voltage even with wide input voltage variations. However, regulation is less precisely regulated than in the switched mode or series-regulated power supplies, but the output voltages are precise and constant enough for many applications.
A ferroresonant power supply is a transformer-based power supply that uses nonlinear magnetic properties and a resonant circuit to provide a stable output voltage over a wide input voltage range. Ferroresonant power supplies are widely used in applications requiring constant output voltages, especially when the input voltage is likely to vary due to instabilities and other power line disturbances. The power supplies can also absorb most of the power line-induced transients.
The power supply is similar to an unregulated supply except for changing a standard single-phase transformer to the ferroresonant transformer, designed to maintain the voltage constant over a wide input voltage range and load current variations.
The ferroresonant transformer consists of an auxiliary secondary winding with a parallel capacitive tank to provide a resonant circuit at the supply voltage frequency. The transformer operation is based on the ferroresonance behavior associated with saturated iron cores in which a further increase in the winding current results in negligible or no increase in the magnetic flux.
The regulation is achieved through the saturation characteristics of the transformer core together with the capacitive tank circuit. The tank circuit stores energy in the form of AC oscillation. This energy sustains the output voltage for brief periods in the order of milliseconds in the event of supply losses or variation. In addition, the tank's circuit acts as a filter to reject harmonics generated by the transformer core saturation.
Advantages of ferroresonant power supply
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Simple design, reduced components, robust and reliable
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Self- current-limiting and self-regulating
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Regulated output voltage over a wide range of input voltages. The output remains constant even at ±40% input voltage or more of the nominal voltage
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Ideal for powering high crest factor or nonlinear loads
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Provides isolation and protection from AC line voltage spikes, surges, and noise. The laminated steel core physically isolates the primary and secondary windings of the transformer. The shunting reduces the capacitive coupling of noise and spikes
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Parallel connection possible for high-power equipment
Disadvantages
The supply is sensitive to line frequency changes, dissipates more heat than conventional transformers, sometimes produces more audible noise at resonance, and is heavier than the transformer in a linear regulated supply.
