Ronk static phase converter faq gas stoichiometry practice sheet

It is a static converter capable of producing symmetrical three-phase currents from a single-phase source. The name, ADD-A-PHASE®, implies a phase is added to the already present single-phase. This is true—and is accomplished by an autotransformer and a capacitor bank along with the motor’s impedance. Through this combination a third phase is introduced whose relation to the other two comprises symmetrical three-phase. The motor can then be made to operate as if it were connected to a three-phase power line.

Standard types are available from 1 through 100 HP. Units up to 150HP have been constructed. Where high horsepower loads are to be operated the power supplier should be consulted to determine that the single-phase line capacity is sufficient to carry the load.

Because of voltage drop, wiring size, starter size, etc., it may be desirable to operate large motors, submersible pumps, etc., at 480 volts when only 240 volt single-phase is available; the Type “3” ADD-A-PHASE® is designed for these applications. Other special voltages are also available such as 240 in/208 out.

The ADD-A-PHASE® draws close to unity power factor while the motor is starting and running, resulting in lower line current and lower losses in line voltage. The inrush current of the ADD-A-PHASE® and three-phase motor is only 3 to 4 times the running current.

Yes. The ADD-A-PHASE® is the only static converter for which this is possible due to its autotransformer design. In fact, continuous overload (service factor) operation is available that equals the permissible overload of the average three-phase motor (1.15). Note: while this operation is possible, some motor manufacturers (notably submersible pump motor manufacturers) may not warranty their motors if it is operated into its service factor range while powered by a phase converter. In practice, it is best to avoid service factor operation if possible to assure normal life expectancy of equipment.

It is not recommended, however, there may be applications where the load of the motor is reduced and within the rating of the converter. Extreme caution should be observed, and it is advisable to contact the factory before attempting such an operation.

The components selected and manufactured for the ADD-A-PHASE® have a life comparable to that of the average three-phase motor. This long life and reduced maintenance is one of the many advantages of the ADD-A-PHASE® over the conventional single-phase motor.

The ADD-A-PHASE®, being a static device with only a few moving parts, is relatively free of maintenance. Should replacement parts be necessary, immediate shipment can be made from factory stocks, or they can be readily acquired from local sources. TECHNICAL

The power factor will be very high during starting, near unity. The ADD-A-PHASE® draws a reduced starting current during starting due to the capacitance built into the converter. Due to this, starting KVA is approximately that of the 3-phase across-the-line starting.

Independent laboratory studies rate the power factor of the converter at almost unity on the single-phase line. This feature is of extreme importance and advantage to both the power supplier and user. On the other hand, repulsion-induction single-phase motors have a power factor range of only 60 to 80%.

No. Swinging load conditions necessitate the phases being balanced on installation for the maximum load. Where the load is reduced due to swinging, the unbalance should be disregarded insofar as none of the phases carries a current exceeding the nameplate rating. Minimal loss of efficiency is normally encountered.

Yes. The voltage that exists, with the converter energized and the motor off, will reflect the autotransformer’s settings. They are only useful for identifying the phases and the tap setting. The motor must be connected, with its normal load applied, to take readings which verify, or can be used to achieve, balanced currents and voltages.

This is not recommended because of the voltages that exist when the motor is off. If over/under voltage protection is necessary, it should be used across the two singlephase power leads only. Current monitors that do not look at voltage can be used, however.

The installation should include a single-phase switch sufficient to carry the single-phase FLA of the ADD-A-PHASE®, plus other auxiliary equipment, if any, on the single-phase line. These fuses must be of the lag type to allow starting of the motor.

Not necessarily. The ADD-A-PHASE® can be located at any reasonable distance from the motor. When the unit is to be located at a considerable distance it may be necessary to increase the wire size to compensate for loss of voltage. Also, “in-sight” rules of Section 430 of the NEC may apply. Consult the converter wiring diagram and NEC before installation.

Satisfactory converter operation requires application of the best converter for the job. Only RONK provides the broad product line and experience necessary to provide a converter for any application providing the best performance at the lowest cost.

ADD-A-PHASE® is usually recommended for single motor applications that operate at constant loads, though there are some exceptions such as multi-speed motors. In these applications, where automated operation is required, the ADD-A-PHASE® is generally recommended. A rotary converter is usually recommended for the operation of a group of motors or motors with varying loads. The rotary converter is also recommended for three-phase resistive, rectifier, or electronic loads.

Rotary converters may be significantly less expensive for multiple-motor applications where load characteristics allow their use. However, additional equipment is often required when rotary converters are used in automated applications, which raises the installation and maintenance costs. The ADD-A-PHASE’s® higher efficiency offers significant savings in operating costs. These savings can offset its higher initial cost.

Generally they can be, however, adjustments are available on both the ADD-A-PHASE® and ROTOVERTER® for balancing of all three of the phase currents. The ROTOVERTER® is the only rotary converter that provides this capability. QUICK LINKS Required Information for a Phase Converter Quote