Static Phase Converter vs Rotary Phase Converter

Static Phase Converter vs Rotary Phase Converter

Phase conversion is the procedure when phase converters run enginery by changing single-phase current to three-phase current. The device is widely used with phase converters to produce three-phase current in houses and other industries. Many industries still have single-phase current and are not allowed for adding more current phases. In addition, due to better quality of three-phase current, three-phase converters are prefered by most users.

In the United States most industries have single-phase current. This is electricity or as it is also called AC electric current. In the 20th century double-phase electric current was produced, but in the 21st century a three-phase electric current has been more widely used than double-phase in the industry. Due to the phase-converter the single-phase circulation is changed into a three-phase source. This helps industrial supplication to be used safely.

Single Phase Power Supply 3 Phase Power Supply

types of Power Supply

  Phase 1    Phase 2    Phase 3

Static Phase Converter vs Rotary Phase Converter

Nowadays, Static and Rotary phase converters are widely used in the industry.

However, you should differentiate between their functions to choose the correct one for your device or machine.

Static Phase Converter and how does it work?

A static phase converter is used for starting the machine or device working. It has a simple construction when its condenser starts a circulation that helps the three-phase converter to work immediately.  It has two factors for its work:

Static Phase Converter

  1. A voltage sensitive relay ( is used to turn on between two condensers to help the engine to gain the speed;
  2. One and more condensers.

Static phase converter produces the electricity for machines that are used in homes or shops:

1. Sewing machines

2. Vacuum pumps;

3. Ventilation systems;

4. Small air compressors; 

5. Printing device;

6.Food processing devices;

7. Wood- / Metalworking devices, etc.

Note* The Static phase converter CAN’T be used for the Computer Numerical Control machines (CNC). 

The PROFITS of using the static phase converter are:

  1. Its price is little;
  2. You are able to start three-phase devices ( as long as they don’t exceed ⅔ of the HP range)

However, there are also drawbacks of using static phase converter:

  1. Not all the device can work with the static converter;
  2. The device won’t work smoothly, because it will get a three-phase electricity. 

how does work static phase converter

Rotary Phase Converter

Rotary Phase Converter and its functions

Rotary phase converter is widely used in the industry. This converter includes a three-phase engine and condensers that are pumped up together to work like one big condenser.

Two main engines are tied to the single-phase engine and the other engine is connected to the condensers. Output leads are tied across the engine terminals. 

Rotary phase converters are used for metalworking device as CNC (Computer Numerical Control machines) and  wire EDM’s (Wire Electrical Discharge Machining)

how does work rotary phase converter

Rotary Phase Converters and their Work with CNC machines

Rotary phase converters are used for work of Computer Numerical Control machines (CNC).

CNC machines take an important place in the production industry. These machines supply an accuracy that is possible to achieve due to their work.

A rotary phase converter helps to balance voltage. When a CNC machine works due to a rotary phase converter, the voltage imbalance should be reduced in the converter. To achieve a balanced work of CNC machines, Rotary phase converter should be used with Voltage Stabilizer. 

A rotary Phase Converter and Voltage Stabilizer helps to keep the necessary voltage balance. Voltage Stabilizer also helps to keep the voltage steady during the work of device, thus helping CNC/PLC (Programmable Logic Controller - a computer box that controls the work of CNC machine) to work effectively.

What phase converter should be used?

You should remember that the device will produce  ⅔ of its rated when running on the Static converter. If the device is loaded beyond ⅔ , a rotary converter should be used. Otherwise, you should unload the engine by reducing the engine pulley diameter by 1/3 or increase the horsepower by 50% to accommodate the loss of current.

Which HP range to choose?

To choose the phase converter for your device correctly, you should know what HP range to choose.  The largest engine on the device must fall within the minimum and maximum ranges of the converter. Two-speed engines usually have dual horsepower. For instance: A 3 HP 3600 RPM engine is 1.5 HP at 1800 RPM. You should select a converter with a minimum and maximum range, which will accommodate both horsepower ranges. 


  1. The first engine to start working on the converter must fall within the minimum and maximum horsepower range on the converter. However, after the first engine is started working, engines below the minimum range may be started and can usually be left running as the main engine is stopped and started.
  2.  Do not add the horsepower of the current feed, coolant pump, or other accessory engines when sizing a converter. You can add the horsepower of two or more engines together if they always start working at the same time. 
  3. A larger size converter won’t produce greater horsepower than a less size converter. Also, a Static Converter won’t work with a Heavy loaded device that consists of pumps, fans, compressors, hydraulics, etc.

The static phase converter won't be able to produce the current for more than one machine. The rotary phase converters can produce an amount of device. That’s why static converters work with  the machines that have less electricity current. Rotary converters with bigger devices and machines. 

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