Sinrace Power Supply Technology (Shenzhen) Co., Ltd.

A frequency converter is either a motor/generator or electronic device that accepts AC power at one frequency and regenerates AC power at a differing frequency.

The Frequency Converter diagram above shows a typical design where the incoming AC at a specific frequency is rectified to a Direct Current (DC). The DC is then fed to a Pulse Width Modulated (PWM) Inverter stage where sinewave AC power is created at the desired output frequency.

Motor/generator (MG set) frequency converters are primarily designed for large fixed applications such as aircraft ground power or large equipment designed for use in another country. Due to their size and weight, they are a poor choice for portable applications. Electronic frequency converters consist purely of electronic circuitry. They take the incoming AC power, convert it to DC, filter it and regenerate new AC power at the desired frequency. The converters range in size from low cost, small portable units up to large models for fixed installations. Their output voltage and frequency regulation is typically superior to the motor/generator types. Most products range in size from 1-6kVA and are ideal for portable and small fixed applications. Typical applications include 400Hz power sources for small avionics and military labs, and 50Hz or 60Hz sources for powering frequency sensitive computers, networks, telecommunications, satellites and radio equipment. For applications requiring both conversion and on-line power protection, there are a select few true on-line models which provide three-phase to single-phase conversion, 50/60 and 400Hz frequency conversion, voltage conversion and optional battery backup capability for a complete power solution.

When choosing a frequency converter, understanding the equipment’s requirements and capabilities is key to finding the right fit. If the equipment is required to perform in an international environment, weigh the cost of the converter against the cost of replacing the equipment to be powered. Care must be taken to assure it is sized properly to meet the power demand of the connected load(s). Over-sizing the converter a bit is always a good practice. If selecting a low-cost converter, verify it has a true sinewave output with less than 5% Total Harmonic Distortion (THD). Never use a converter with a quasi-sinewave, step-wave, square-wave or modified-sinewave output.

For specific information on international voltage, frequency and plug standards by country, visit