How Does a Phase Converter Work?

By Michelle Kerns, eHow Contributor

 
 
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How Does a Phase Converter Work?

1. Aspects

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     Phase converters are devices that are capable of taking single-phase electrical power (current in which the voltages of all the sources of supplied power are synchronized) into multiple phase electrical power. The most common phase converter transformation is from single-phase to triple-phase power, in which the currents of electricity delivered from three different power conductors peak sequentially, each approximately 1/3 of a full cycle behind the other. There are three main types of phase converters: digital-phase converters, rotary-phase converters and static-phase converters.

   Function

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     While all three main types of phase converters generate 1/3 voltage that they add to the two voltages present in single-phase power service, they accomplish this in different ways.

     Rotary-phase converters use a separate, three-phase motor and a group of capacitors which together function as one large capacitor. The single-phase source of electricity is attached to two of the three phase motor leads. The third lead to the motor is attached to one of the single-power source outputs in series with the group of capacitors, and the output leads from the rotary-phase converter connect to all three-motor terminals. In this way, the rotary-phase converter generates 1/3 source of power while simultaneously combining it with the other two currents from the single-phase power source.

     Static-phase converters produce a third phase current, supplementary to the currents from the single-phase power source, only while the item being powered is being started and cannot be used for long-term, three-phase power needs.

     The most modern type of phase converter, the digital-phase converter, differs greatly from the other two main types of converters in that they are entirely electronic--they produce the third voltage through a process known as the double-IGBT conversion, in which alternating current from the single-phase power source is converted to direct current, then back to alternating current. A digital signal processor constantly monitors the three currents.

   Significance

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     While single-phase electrical power is sufficient for most small, rural areas and when electrical needs are confined to heating and lighting as opposed to powering large-scale electrical motors, three-phase power is essential for powering large office buildings, factories, shopping centers and urban residential areas.

     Three-phase power service is not readily available in many locations, because to provide it requires utility companies to install higher voltage transformers, alternative service panels and separate wires. When they do offer three-phase service, it is therefore usually at a higher utility price.

     Phase converters provide a way for people in areas that only provide single-phase service to power large electrical machines, such as farm equipment.