Phase Converters have a diverse range of applications and are found in many sectors of society. If electric motors offer to relieve the high maintenance schedule of gas engines or they present a cost-effective alternative to your operation, then phase conversion should be your first consideration. Commitment to quality, adaptability in design, and a desire to meet the specialized needs of our customers, has lead to Willett Manufacturing becoming a leading manufacturer of Phase Converters in Canada. Willett products provide you with years of maintenance free operation.
The Phasor is a static (non-moving) phase converter. It essentially consists of an enclosure containing the "Willett Power Pack", capacitors, and relays. It is primarily designed for single motor applications. More than one motor may be operated at one time in some cases, but each application must be sized individually to prevent damage to the motor and converter. Multi-motor operation really lies within the realm of the Willett RotaDyne. The Phasor supplies an out of phase current wave by splitting a single-phase lead, thereby forming a third current path sufficient to start the motor. Once the motor is started, the Electro- magnetic field (E.M.F.) from the running motor holds a power relay open to disconnect the starting cycle and the motor continues to run on single phase power with a capacitor produced third phase. Instant reversing characteristics are maintained with a static converter. The motor rpm is not affected and most two-speed motors can be run. Starting current drain of a Phasor is about 20% comparative to the same size single-phase motor.
Sizing the PhasorCare must be taken when putting together a static converter/electric motor system. It must be noted that this type of system will produce two thirds of the electric motor's rated horsepower. For example, a fifteen horsepower motor coupled with a 15 horsepower Phasor will develop 10 horsepower at the shaft. Energy consumption remains equal to the supplied horsepower equivalent or 10 horsepower in this case. The Phasors horsepower rating must equal that of the electric motor. Motors operated with a static converter can have slightly less starting torque than when operated on regular three-phase power. This is a consideration when sizing the converter, particularly when the load is hard to start. To overcome hard start loads the heavy duty Phasor or the next larger size of standard Phasor-motor combination should be purchased.
Light Duty: The light duty Phasor or UY series is for applications where the number of starts and stops are infrequent. Tools operated four or five times an hour would be such an application.
Heavy Duty: The heavy duty Phasor or Y2 series is used for frequently started or jogging applications such as compressors or hoists.
The following chart provides the Model Number of the Phasor that will match the horsepower of your motor, (Remember, this matched horsepower will be derated by one third). When choosing a phase converter, Willett recommends that you call the factory with any questions about sizing or applications. There may be simple features or adjustments available that can make your converter more efficient for your application.
* Also available in 230 Volt.
Power RequirementsPower supplier transformers should have 1 KVA capacity per effective connected horsepower over and above other single-phase motors.
Inrush CurrentsA Phasor unit and a three-phase motor will require approximately 350% of the full load nameplate current rating for starting. This is to be compared with inrush currents of 600% for single-phase motors. Power suppliers generally limit single-phase motors to a 10 HP maximum because of the effects to their lines during starting periods. The Phasor and three-phase motors are far more common in horsepower ratings 5 and up.
Efficiency and Power FactorThe overall efficiency of the three-phase motors run from single-phase lines with the use of a Phasor is lowered by almost a negligible amount . Small imperfect losses occur in the capacitor panels and relay coils. As compared to a three phase motor on three phase lines the Phasor/motor combination works more efficiently during starting and under normal load because of the leading power factor on start and the unity power factor under full load. This means all the metered power is truly useful power. The ratings of three-phase motors normally range in the upper 80's to lower 90% efficiency. Single-phase motor efficiencies are much lower, at 65 - 75%.
TorqueA Heavy Duty model Phasor paired with an equally sized three phase motor can exhibit only slightly less locked rotor torque for starting than the three phase motor on three-phase lines. Since the Phasor/motor combination operates at 2/3 of their rated horsepower, the starting torque is adequate for most properly sized applications. To overcome heavily loaded motors with starting problems:
Select a design C or D electric motor for better starting torque characteristics since the electric motor may not have enough torque for the application.
Forward- Reverse Applications with the Phasor
One of the biggest advantages of three-phase motors over single-phase motors or gas engines is instant reversing. Simply interchange any two motor leads and the motor is reversed. Heavy-duty Phasors, Forward-Reverse switching and an appropriate sized contactor are required for this application.
Two Speed Motor Applications
Two-Winding (Two-Speed Motors) require a Phasor that is matched to the smallest horsepower rating of the motor.
With Single-Winding, Constant or Variable Torque Motors (reconnectable pole type), the smallest HP must be matched to the Phasor unit. We recommend you contact the factory when using this type, as these motors have some torque limitations and must be adapted correctly to ensure satisfactory operation. Heavy-Duty model Phasors must be used with this application.
The Standard Phasor consists of the "Willett Power Pack", capacitors and relays. A general-purpose enclosure (12" x 12" x 6") is used that is suitable for indoor mounting under dry conditions. Standard input/output voltages are 230-240 and 460-480 VAC.
In addition to the features of the Standard Phasor, the Complete Phasor includes a selector, magnetic starter, and thermal overload protection.
The Auto-Phasor is a static converter that allows you to utilize 90% of the matched converter/motor horsepower rating. In other words, a 10 HP motor matched with a 10 HP Auto-Phasor will develop 9 HP at the motors shaft.
Combination Motor Controller/Phasor
This model includes a main disconnect, magnetic starter, stop-start or selector, provisions for remote switch, and a standard converter contained in a dust-tight or weatherproof enclosure. Alterations are available to meet customer specifications.
The Phasor may be ordered for applications requiring special enclosures, as well as motor protection and control as part of the unit. A special Phasor is also built with over-current, overload and single-phase protection, complete with a lightning arrestor, all in a CEMA 3 or 5 enclosure to be used on oilwell pumpjacks or irrigation systems.
We offer a variety of enclosures for special applications:
600 VAC models are available on special request.
A transformer is also available for voltage conversion in special applications. A voltage variation of more than 10% above or below the normal rating will affect both converter and system performance.