Rotary Converter

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   Static Phase Converter Application Notes

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The most important question is whether or not the motor is heavily loaded. You must keep in mind the fact that the motor will produce approximately 2/3 of its rated horsepower when running on the static converter. If the motor is loaded beyond that point, you must use our Rotary Converter, or use method number 2 as explained in the Installation Instructions. Otherwise, you must unload the motor by reducing the motor pulley diameter by 1/3, or increase the motor horsepower size by 50% to accommodate the loss of power.

For further information or verification of proper sizing, contact Phase-A-Matic, Inc.

NOTE: For the following outlined applications you MUST use a Rotary Converter:

Battery Charger Plasma Cutter Some CNC Equipment
EDM Machine Radar Transmitter (Radio & Television)
Heating Elements Rectifier Variable Frequency Drive
Laser Rheostat Welder

Next you must determine whether to use a Regular Duty or Heavy Duty converter. Keep in mind you can always use a Heavy Duty converter in place of a Regular Duty one. A Heavy Duty converter will not provide greater horsepower. However, there are some static converter applications for which you should always use the Heavy Duty series. 

These are:
1. Frequent starting (more than once a minute).
2. Instant reversing.
3. Unattended equipment, such as air compressors.

Long, heavy starting cycles, such as lathes without a clutch, flywheel driven equipment, etc.

5. If jogging is required.

If there is a chance of the motor being stalled during use (woodworking equipment, etc.).


Next, you must find the proper horsepower range for the application. The largest motor on the machine, or idler motor if used, must fall within the minimum and maximum ranges of the converter. Two speed motors are usually dual horsepower. For example, a 3 horsepower 3600 RPM motor is 1-1/2 horsepower at 1800 RPM. You should select a converter with a minimum and maximum range which will accommodate both horsepower ratings. However, with Taiwanese and Chinese motors, the larger horsepower should be at the lower range of the converter whether it is a two speed motor or not. For example, for a 5 horsepower Taiwanese motor you should use a 4-8 horsepower range converter, even if it is a two speed motor with 2-1/2 horsepower on the low speed. This is because Taiwanese and Chinese motors draw more amperage during start than do domestic motors and therefore require a slightly larger converter than would normally be used. A larger size converter will not provide greater horsepower.

  A Few Additional Items to Remember:

The first motor to start on the converter must fall within the minimum and maximum horsepower range on the converter. However, after the first motor has started, motors below the minimum range may be started and can usually be left running as the main motor is stopped and started.


Do not add the horsepower of the power feed, coolant pump, or other accessory motors when sizing a converter. The only time you would add the horsepower of two or more motors together would be if they always start at exactly the same time.


A larger size converter or a Heavy Duty series converter will not produce greater horsepower than a Regular Duty converter.


Heavily loaded equipment usually consists of equipment with pumps, blowers, fans, compressors, etc.


If further technical assistance is required, contact Phase-A-Matic, Inc. for assistance at 661-947-8485. Our business hours are Monday through Friday 8:00 AM to 4:30 PM Pacific Time.



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