Page 3 of 5 pages on selecting the right converter. Page one is here.

Ronk Electric Industries

     When I first started promoting the transformer method I found there was a lot of skepticism about it. There was only one manufacturer building and selling transformer converters – Ronk Electrical Industries. 

    They also sell rotary converters and have been in business since 1952.

     I think this is another manufacturer that doesn’t go in for flashy ad copy and they don’t seem to aggressively go after the retail market.

     I doubt they are trying to compete on price.

     It looks like a manufacturer that has government and commercial customers that pay for the quality and service.

Remember that sometimes they refer to a static converter they are actually describing the transformer converter.

     So below is from the Ronk website and I have cut and pasted this abridged edition. I have put in my opinions in purple text.

     You can go to the website here. Ronk Electrical

     RONK ELECTRICAL INDUSTRIES pioneered single-to-three phase conversion with the introduction of the ADD-A-PHASE® converter in 1952. This converter has proven so reliable that it is still widely specified today to power a wide range of three phase loads from single-phase utility power. The TYPE HE-AA (automatic adjust) ADD-A-PHASE® increases applications for a static type auto transformer–capacitor converters to include equipment whose loads vary more than 50%, such as the hydraulic elevator. A load-sensing circuit allows the run capacitors to be automatically switched in and out with changes in the elevator motor’s load requirements. In this way, the TYPE HE-AA ADD-A-PHASE® converter maintains very reliable current balance to the motors that operate under variable load conditions.

This is something that everyone has been working on. 

Remember that in the previous page, Gary Werner from Smith Electric, totally trashed the above method of switching capacitors in and out. 

Below Ronk talk’s about the transformer converter used in elevator service.

     Phase conversion for elevator motors has normally been handled by a rotary phase converter– which is what most converter manufacturers’ produce. The TYPE HE-AA ADD-A-PHASE® allows the hydraulic elevator manufacturers to realize the advantages that the autotransformer-capacitor type design offers over rotary phase converters.

Higher reliability

     Rotary phase converters may prove problematic in insuring the reliability required of elevator systems. To increase energy efficiency, rotary converters are equipped with automatic controls such as timers and relays to initiate the elevator motor only when demanded. This increase in electromechanical content further compromises system reliability.

Greater efficiency

     Rotary phase converters, with or without automatic controls, are considerably less energy efficient than the TYPE HE-AA ADD-A-PHASE® converter. This is due to the fact that their rotating elements (rotors) must be maintained during no-load conditions, resulting in much higher idle losses. Another concern with rotary converters is that they do not normally balance phase currents and this imbalance forces inefficiencies in load motors. Overall efficiency is determined by the efficiency of the converter and efficiency of the load. The ADD-A-PHASE® type converter is 97% efficient and the no-load losses in the TYPE HE-AA ADD-A-PHASE® are limited to very small excitation losses in the auto transformer. A 15 HP TYPE HE-AA ADD-A-PHASE®, for example, would only be producing about 60 watts of no-load losses. The TYPE HE-AA ADDA- PHASE® converter maintains great current balance, allowing the motor to operate very efficiently.

Fast response

     From an at rest state, the rotor of the rotary converter must be accelerated to its synchronous speed before the elevator motor can be initiated. This normally takes between 3 – 10 seconds. By contrast, the TYPE HE-AA ADD-APHASE ® converter is constantly energized, providing immediate response for the elevator motor and not allowing sag in the system.

Quiet operation

     Electromechanical systems such as the rotary phase converter can generate mechanical noise. Sources of noise include the windings of the moving rotor, movement between the converter’s capacitor shroud and frame and rotor magnetizing current whine during no-load/under-loading of the system. Rotary converter noise levels will also increase as the converter’s bearings wear. The TYPE HE-AA ADD-A-PHASE® converter has only one moving part – a switching relay – which produces very little noise.  Newer electronic phase converters and drives produce harmonics which can contribute to problems in the facilities electrical distribution system. The TYPE HE-AA ADD-A-PHASE® does not generate harmonics!

The above points are exactly what I found desirable about the transformer converter.

No rotary to start before starting your motor, quiet operation, full starting torque.

      The phase converter and the four or six inch submersible pump motor have been quite successfully applied to rural single phase lines for many years. It is necessary to recognize the special characteristics of the submersible pump motor and also the characteristics that are encountered whenever this motor is operated from a phase converter. These characteristics must be considered in determining the proper size of phase converter for the submersible pump motor.

The 3-phase submersible pump motor

     The submersible pump motor is a very special unit. They are normally manufactured in diameters of four or six inches. They are, by necessity, sealed from the fluid that surrounds them. The diameter limit means that the motor must be lengthened in order to build an increased horsepower rating. The long slender design results in potential vibration problems which are not normally encountered in above ground motors. The motor being installed in the fluid affords the motor a constant ambient temperature and also the flow across the unit aids the motor in cooling. These motors do not follow standard full load current ratings which apply to equivalent above ground motors of the same horsepower and speed. The submersible pump motors will have a “maximum current rating” which includes the service factor amps of the motor and it can be expected the motor may operate near this maximum rating.


Above ground motor Submersible pump motor

10 HP – 230 volt – 3 phase – 26.8 amps 10 HP – 230 volt – 3 phase – 36.0 amps

15 HP – 230 volt – 3 phase – 39.2 amps 15 HP – 230 volt – 3 phase – 51.0 amps

     The phase converter and the four or six inch submersible pump motor have been quite successfully applied to rural single phase lines for many years. It is necessary to recognize the special characteristics of the submersible pump motor and also the characteristics that are encountered whenever this motor is operated from a phase converter. These characteristics must be considered in determining the proper size of phase converter for the submersible pump motor.

They must sell to a lot of people that use submersible pumps.  I always was a bit nervous when I found that one of my customers wanted to build a transformer converter to run something like that.

In good faith I could not tell them “Oh, yeah, it will work great for your $10,000 pump.” 

A transformer converter would be ideal, but I didn’t know if the person on the other end of the phone could really build one right.

I would always tell those customers that they should seek professional guidance.

Static phase converters

      Static phase converters are normally manufactured in two styles. They are the straight capacitor design or in the autotransformer-capacitor type design. The straight capacitor is not recommended for the submersible pump motor. The autotransformer-capacitor type should be used.The autotransformer-capacitor design is the unit most commonly applied to the submersible pump application. This time and field proven device is capable of operating a 3-phase motor at 100% rated horsepower on a single phase line. The unit consists of an autotransformer, running capacitors,starting capacitors and a contactor to take the starting capacitors out of the circuit after the motor is up to speed. These type units must be sized properly to obtain satisfactory operation of the 3-phase submersible pump motor on the single-phase line. The maximum ampere rating of the submersible pump motor determines the size of converter required. This maximum ampere rating should be compared to standard above ground full load ampere charts of 3-phase motors to determine the equivalent size of phase converter required. Some manufacturers of this type phase converter have specific types recommended for submersible pump motors.The submersible pump motor is and has been a common and successful application for the autotransformer – capacitor phase converter for 40 years.It has been widely applied throughout North American. Submersible pump motors normally have a high power factor, in the vicinity of 80-90%, resulting in the use of higher autotransformer taps . The phase currents can be adjusted well within the 5% current balance required.This type converter has excellent power line characteristics. The full load single-phase power factor, with the motor operating, will be near unity or slightly leading depending upon line characteristics, the load, the length and size of conductor between the converter and the motor. The starting current will be 2 ½-3 times the full load rating of the converter on the single-phase line and the power factor will be leading during starting. Submersible pump motors normally start in less than one second from this type of converter. Any submersible pump motor operating continuously, such as an open discharge,can be operated with excellent motor phase current balance.The phase currents should be checked carefully and the necessary steps taken to bring the motor and converter into an acceptable balance. This may necessitate adding or removing capacitors or adjusting the transformer tap of the converter for best balance.The main disadvantage of applying the submersible pump motor to the autotransformer-capacitor style converter is that current balance can be achieved at only one load condition. If there is a wild fluctuation to the load,on which the submersible pump motor is applied, the phase currents will go out of balance.The autotransformer-capacitor phase converter can be manufactured with a very unique feature. It can be designed to operate a 460 volt 3-phase submersible pump motor from either a 230 or 460 volt single-phase line. This feature will result in considerable savings during installation, particularly if only 230 volt single-phase is available to a deep set submersible pump motor.Use of the 460 volt 3-phase motor on the 230 volt single-phase system will result in much smaller wire size and a smaller pump control than would be used on the 230 volt 3-phase installation from the 230 volt single-phase line.

     The autotransformer-capacitor style converter has very low power consumption when the motor is not operating. The core and copper loss of the autotransformer are the only losses. For example, a 15 hp unit would dissipate about 60 watts.The starting capacitors utilized in this type of converter furnish approximately 150% starting torque to the submersible pump motor.

Rotary phase converters

     Rotary phase converters are manufactured in two types. They are the non adjustable rotary transformer and the adjustable rotary transformer designs.Both units have been successfully applied to 3 – phase submersible pump motors on single-phase lines. Either the non-adjustable or adjustable type rotary converters consist of a rotary transformer (aka: motor) and one or more capacitor banks.The non-adjustable rotary converter has limited control of the motor phase currents. It is somewhat possible to adjust the phase currents by varying the amount of capacitance in the circuit; however, only moderate success is achieved in this procedure. In many cases it is not possible to obtain current balances within the 5% tolerance recommended for submersible pump motors.

      The adjustable rotary converter does enable the installer to adjust the phase currents to within the 5% recommendation. This is accomplished by adjusting the rotary transformer taps and varying the amount of capacitance for a proper phase balance. This gives a distinct advantage in that the phase currents will be better balanced over the load range of the submersible pump motor. As such, mechanical motor vibrations caused by negative sequence currents will be minimized.Installation considerations The properly installed rotary converter on a submersible pump should have a single-phase safety switch or circuit breaker anda magnetic contactor ahead of the converter. The output of the converter should follow the submersible pump motor manufacturers specifications with respect to size of the starter, overload protection, and size of the conductor for the depth of the pump setting. Rotary converters develop very low starting torques and on any submersible pump application that might require high starting torque, it may be necessary to add a starting panel to the installation. If the starting panel is needed it should be connected to the load side of the magnetic starter. The starting panel, when wired in at this point, will get the motor up to speed in 2 or 3 seconds and automatically disconnect itself from the circuit when the motor reaches full speed.

Note: Here is a link to a complete FAQ from the Ronk Phase Converter company. This is straight from the horses mouth about the transformer converter. Ronk is the only company in the world today that produces models of the transformer converter.


All of the above is good reading and they tell it like it is. Remember these are people that sell both the transformer converter and the rotary. They have experience in both.

Next stop is American Rotary