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Questions & Answers

1. Does it generate constant frequency and voltage?

2. VSI Generator cost compared to induction type

3. Comparison of output per unit weight

4. Efficiency versus range of rpm

5. What does overspeed capacity mean?

6. What are the comparative effects of the VSI Generator?

7. Can the VSI Generator be used for starting purposes?

8. Does the VSI Generator offer any other advantages besides a wide speed range?

9. Is the power factor and VAR support affected at variable rpms?

10. What are the major advantages of the VSI Generator?

11. What are the starting amperes necessary to energize the windings of the VSI Generator?

12. Can slow multipolor, VSI Generators be manufactured?

13. What about speeds above 200% of base speed?

14 Does the VSI Generator require a special design to fit an application?

15. How does the VSI Generator effect peaking at the utility company?

16. Can the VSI Generator be utilized with anaerobic digestion and fluctuating Btu?

17. Can the VSI Generator be used in hydroelectric power plants?

18. Does generator require special design to fit a need?

19. Can the VSI generator be used in wind turbine applications?

20. Are there other applications for the VSI Generator unit?


1. You call it a Constant Frequency and Voltage generator. Does it generate constant frequency and voltage regardless of the rpm it is driven?

Ans. Yes, within the designed range of speed. This means above the base speed. Actually it always generates the frequency and voltage with which it is excited (line frequency). That is the key to the VSI Generator patents. This means that if the output of the VSI Generator is fed into a 50 Hertz line, it always generates 50 Hz; into a 25 Hertz line, 25 Hz, and of course, into a 60 Hertz line it will deliver 60 Hertz. back

2. How does the operation and cost of the VSI Generator compare with an induction generator?

Ans. Although the VSI Generator is similar to an induction generator in its construction the similarities end there. Although the VSI Generator can perform as an induction (squirrel cage) generator, the opposite is entirely untrue – so how can they be compared?

The standard fixed speed induction generator (plus or minus approximately 3% of a fixed rpm) is a simple unit and should be used where a constant speed is controlled and available. But as soon as you mention 15%, 30% or 100% change in speed, you have no comparison. So how can you compare costs with a non-existent device?

If you want to compare the VSI Generator to the electronic controller necessary for a standard induction system, then the costs of the VSI Generator are from 1/3 to 1/5 as much. Electronic controls represent the weak link in the induction generator system. The servicing of such a device, when it needs repair, can take weeks or months and the cost can exceed thousands of dollars in “down-time” not including the actual repair costs.


3. What is the output per unit weight size comparison?

Ans. Compared to an induction generator, the VSI Generator is approximately 15% lighter. The following is a comparison between standard AC generators and the VSI Generator power ranges. Note: An individual VSI Generator has the ability to produce power incrementally and at variable rpm's without speed controls. It would take multiple standard generators running in conjunction with different power ratings, pole counts and with speed controls to duplicate the basic characteristics of a single VSI Generator.

For example: A 4 pole VSI 3-10 can produce from 1 KW to 10 KW at speeds ranging from 1800 to speeds beyond 3000 rpm. In order to duplicate this extreme kilowatt output and wide speed range you would need a minimum of four standard AC generators with at least four different power ratings, several different speed configurations, electronic and mechanical speed controls and a combination of 2 and 4 pole standard generators running in parallel.

Four AC generators to = one VSI VSI Generator

1 KW

3 KW

5 KW

10 KW = VSI 3-10 = 3kW-10KW

15 KW

20 KW

25 KW

30 KW = VSI 10-30 = 10kW-30kW

35 KW

40 KW

50 KW

75 KW = VSI 30-75 = 30kW–75kW

100 KW

125 KW

150 KW

200 KW = VSI 75-200 = 75kW-200kW

200 KW

300 KW

400 KW

500 KW = VSI 200-500 = 200kW-500kW

500 KW

750 KW

1,000 KW

1,500 KW = VSI 500-1500 = 500kW-1meg

The VSI Generator increases efficiency, that is it eliminates the need to start an additional unit to produce power when the original unit reaches capacity. For example: In a standard power plant with a capacity of 1000kW, if the demand exceeded 1000kW the plant would have to put another unit on line to meet the demand. With a 1000kW VSI Generator running in the same plant, all the plant would have to do is increase the output speed of the turbine (prime mover) and the VSI Generator would pick up the load to a maximum output capacity of approximately 1200kW. This 20% increase in output coupled to the savings to the plant operator of not having to fire up another generator produces the increase in efficiency. back

4. What is the efficiency versus the rpm range?

Ans. The efficiency of the VSI Generator must be considered while operating at variable speeds, the fall-off efficiency with increased RPM is acceptable only as long as there is a relatively flat high efficiency range. In effect, the design point cannot be a single point but must rather be an acceptable range, to be able to achieve the same power output over that range as other generators with different methods of control.

To illustrate: If a 5 H.P. 3 phase motor has a base speed of approximately 700 RPM and is 91% efficient, A properly designed VSI Generator will have about the same efficiency up to a 10% to 15% increase in RPM, and at double the base speed will still be within 75% to 85% of the original efficiency. The VSI Generator, nevertheless, can utilize variable speed prime movers and other energy sources which the traditional standard generator is unable to harness.


5. What is overspeed capacity?

Ans. Because the VSI Generator unit is NOT speed dependent, that is, it does NOT suddenly drop its load as an induction generator does, it does not need overspeed protection. The VSI Generator power system is designed to gradually decrease its load. If the current starts to rise – overload relays will trip the generator off the line. In any case, the width of the rpm range is easily within the control capabilities of almost any type of overspeed controller, mechanical or electrical. back

6. What are the comparative effects of the VSI Generator?

Ans. Under the present method of generation of electricity, the common practice of the utility companies is to have banks of generators operated by low speed steam turbines that are producing electricity at a regular consumption rate. For the peak demand periods, additional generators are maintained on a standby basis and are employed during the peak periods. The common prime movers for such generators are gas turbines because they can be put on the line on extremely short notice so as to meet the sudden surge in the power demands of the consumers.

Low speed turbines strictly controlled to rotate at 3,600 RPM show a productive output per unit of fuel burned (heat generation) of some 34%. A high speed turbine has a productive output of over 38%. However, gearing a high speed turbine to provide 3,600 RPM to a generator causes a loss of some 8% in transmission gears. For this reason only low speed turbines are used by utilities. The gas turbines are substantially less efficient putting out some 25% of heat generated as electric energy. Thus, the kilowatt hour production during peak hours is costing utilities some 136% per kilowatt hour of the normal production.

With the AC Synchronized VSI Generator operating at any speed and capable in the design of producing an increased output of energy through acceleration, the auxiliary generators will no longer be necessary and high speed turbines can be exploited.

To illustrate the difference in figures, if we assume that the current cost of production of one kilowatt hour is one hundred something... then the peak production will make the cost of power to be 136. So that during the peak hours we will have a combination of 100 kilowatt hour cost and 136 kilowatt cost. If we assume that the increase in production was 30% and lasted four out of twenty-four hours, every day, then the total average production costs per kilowatt hour will be 103. With the AC Synchronized VSI Generator using a high speed turbine which is 11.8% more efficient than the conventional low speed turbine, using the same 100 as the base cost of kilowatt hour, the cost will be 84.74. With the same generator to generators being capable of an increased output, there will be no need for auxiliary generators and gas turbines so that the increased production during peak hours will maintain the same cost of 84.74 per kilowatt hour. Thus, disregarding the exotic devices for generating power, such as windmills, geothermal power, etc., if the AC Synchronized VSI Generator were utilized today, in all fossil-fuel plants, and were producing power at current levels, the reduced fuel consumption would mean that the present consumption with the conventional generators would be 21.55% higher than the AC Synchronized VSI Generator.

For example: AC Synchronized VSI Generators consuming 100 barrels of oil a day will be producing the same power that the conventional generators would produce with 121.55 barrels of oil. Needless to say that in addition to more economical consumption of fuel, this would substantially effect the importation of foreign oil into the country. back

7. Can the VSI Generator be used for starting purposes?

Ans. The VSI Generator can be used for starting purposes, for wind turbines and other turbines. As previously stated, stated the VSI Generator acts as an induction motor, but with the advantage that it does not require the 6 to 8 times full load rated inrush current to develop full torque and thus has a major advantage over other machines in this respect. back

8. Does the VSI Generator offer any other advantages besides a wide speed range?

Ans. The VSI Generator can be designed to make the output watts curve follow the "cube" law to a remarkable degree. No other equipment approaches this parameter without excessively complex and costly controls. back

9. Since this is an inductive device, windings around an iron core, is the power factor and VAR support difficult to keep up to a reasonable level?

Ans. The majority of VSI Generators give the power factor in the high 90’s for units with extreme speed range we use NEMA recommended kVAR (kiloVolt Amperes Reactive) values for motor hp. The impact of reactive kilovars on power interchanges between independent power producers and utilities. The intent of many power purchase contracts calls for the producer to stand ready to provide 62 kilovars (kvar) of reactive with every 100 kilowatts (kW) of power. This particular kvar/kW ratio is equivalent to an 85% power factor.

Figure 1 illustrates the power factor equivalents of various kvar/kW ratios.

Figure 2 depicts three operating scenarios. The first case illustrates a situation where an independent producer is providing adequate var support, a case where power is being delivered with no var support (no kvar) and a third case where the producer is selling power and purchasing vars.

In the first case, everything is in reasonable balance; however, in the second and third cases, the utility has had to bring on additional generation solely to provide the reactive megavars required by the combined system loads. If the power producer fails to provide adequate “VAR support,” the utility may be forced to start up another generator for the sole purpose of generating kvar, or if a chronic condition is involved, install a bank of power factor correcting capacitors. In either case, the utility’s “avoided cost” is reduced along with the amount that it can justify paying for the power that it purchases from the producer. These explanation(s) are from a design perspective and from the utility’s standpoint.

From the previous tests of the operation of the VSI Generator it can be observed that the only requirements for obtaining an output are a source of magnetizing VAR’s and a suitable load below the power limit. The power limit for the VSI Generator is significantly larger than standard generators by several times.

The relationship between power and vars for the VSI Generator is illustrated in Fig. 8.


10. What are the major advantages of the VSI Generator?

Ans. (See Applications) Engineers have been subjected to utilizing AC generators that have to keep their rpm within a quarter of 1 percent or better (the synchronous machine) or the type that has to be carefully monitored so that it does not reject its load with an increase of a few rpm (the induction generator). The first type requires the nuisance of accurate speed control; the second type will destroy its prime mover if the maximum speed is not limited. The VSI Generator has neither of the above shortcomings. It answers the dreams of engineers that have been struggling with these problems for more than a century. The VSI Generator will operate at a wide range of speed, will not discard its load and still continue to generate power of the same frequency and voltage as the utility line that it is in parallel with. The VSI Generator will be employed where it displaces synchronous or induction generators and where it will harness power sources that otherwise would not be used.

Conventional AC generators must operate within a narrow rpm range or use variable frequency exciters in order to provide electrical power in phase with the utility power network. Otherwise, the out-of-phase generator must be switched off the system. In any case, to accomplish effective integration into existing power systems, precision must be achieved through prime mover speed control devices. Furthermore, grid protection systems must usually be installed to insure power system stability in the event of generator over or underspeeding.

The VSI Generator has neither of the above shortcomings. It answers the dreams of engineers that have been struggling with these problems for about 100 years. The VSI Generator will run at a wide range of speed, will not discard its load and still continue to generate power of the same frequency and voltage as the utility line it is in parallel with. back

11. What are the starting amperes necessary to energize the windings of the VSI Generator?

Ans. In a “motoring mode” (below synchronous speed), the VSI Generator, acting as a wound rotor machine, delivers the highest torque per ampere of any available alternating current motor, and thus has much less effect on the power utility line (mains). Induction generators usually require about six (6) times or more of the rated output amperes when used as a motor for starting turbines. Unfortunately, a well-designed, efficient, induction generator (not motor) may go to eight (8) times or more of the rated amperes for starting. On small (low capacity) systems this may increase starting time to an intolerable degree because of the large voltage drop.

The VSI Generator is singularly capable of decreasing this high “inrush” required by as much as 70%. Simultaneously, the torque can be increased by more than double the induction generator’s capability, thus shortening the time that the starting load is on the utility line (mains). This phenomenon is caused by the two internal VSI sets of windings in parallel, functioning as wound rotor motors. Wound rotor motors are known for their very low starting current and very high (if necessary) starting torque. Thus, the acceleration time for the turbine to reach its full speed can be made quite short. This will not cause too much, or too long, of a voltage dip, so common when other generators are used. back

12. Can slow multipolor, VSI Generators be manufactured?

Ans. Yes, slow speed VSI Generators can be made, and no, there are no special problems. As with any rotating machine with windings on the rotor, centrifugal forces, bearings, shaft length and size are the parameters utilized by our design engineers. back

13. What about speeds above 200% of base speed?

Ans. Laboratory tests have far exceeded 2.5 times base speed. Presently, the engineering team is designing units to accommodate applications where machinery is required to operate during extreme rpm’s. back

14. Does the VSI Generator require a special design to fit an application?

Ans. Yes. Just as there are four NEMA types of induction motors, designs A, B, C, and D, so the VSI Generator should be matched to get a specific or tailored to the application and requested results. For example: A VSI Generator being driven by a diesel engine that has its most efficient hp output at 1450 rpm. The VSI Generator was matched to give maximum output and efficiency within 50 rpm above and below this speed. Without the VSI Generator the customer would have had to use a 1200 rpm generator and lose more than 18% to 20% of the rated engine capacity, or install belts, pulleys, etc. with their maintenance, replacement problems, and additional losses. back

15. How does the VSI Generator effect peaking at the utility company?

Ans. Many companies have “peaking” generators for the additional power required seasonally - air conditioning, heating or lighting - to save the $10 to $20 monthly charge per kilowatt. These too, have accurate governors to protect the generator and stay in synchronism with the utility power. The VSI Generator eliminates these nuisance controls, and better still, if driven faster, will deliver additional kilowatts when such extra power is needed. back

16. Can the VSI Generator be utilized with anaerobic digestion and fluctuating Btu?

Ans. The biomass people have a similar problem because of the erratic power output of their system. Without the fixed rpm requirement, the VSI Generator can deliver a larger quantity of more profitable kilowatts with much less maintenance. back

17. Can the VSI Generator be used in hydroelectric power plants?

Ans. Waterwheel generators can increase their yearly kilowatt output by taking advantage of the excess water wasted with fixed rpm generators. Like wind turbines, the VSI Generator, with its simple method of changing the maximum rpm-kilowatt output, will give the hydro-generator an entirely new profit picture. back

18. Can the VSI generator be used in cogeneration applications?

Ans. The VSI Generator system of co-generation is causing a great deal of excitement in various countries. The co-generator can now match steam needs and power generation needs to further optimize energy use, steam use and energy production. back

19. Can the VSI generator be used in wind turbine applications?

Ans. The VSI Generator opens a vast new field. The exotic short-lived control equipment of tens of thousands of windmill generators in the U.S.A. alone, will no longer be a perpetual source of problems. back

20. Are there other applications for the VSI Generator?

Ans. The VSI Generator is the only A.C. generator for the production of electric current (without complicated speed controls) in the broad field of uncontrollable sources of energy such as; wind, unimpeded running water, methane gas, biogases and multifuel gas turbines, geothermal, tidal, steam and many others untapped sources of electrical energy. The vast market for the VSI Generator can be subdivided into 33 sectors as follows:

1) Manufacturers of power supply units;

2) Manufacturers of dynamometers;

3) Co-generation - producers or services that use steam in their business;

4) Businesses that create biomass as by-products of their activities;

5) Water turbine systems;

6) Gas turbine systems;

7) Steam turbine system;

8) Wind turbine power generation systems;

9) Solar power generation systems;

10) Wave, tidal and current generation systems;

11) Public Utilities, nuclear, coal, gas, hydroelectric systems;

12) Oil refineries;

13) Producers of methane;

14) Producers of biogases;

15) Geothermal systems and ocean thermal energy conversion;

16) Superconductor technology systems;

17) Communication systems;

18) Medical facilities;

19) Transportation systems;

20) Mag-lift technology systems;

21) Control systems;

22) Fuel cell technology;

23) HVAC/compressor bases systems;

24) Residential Home Owners and Builders;

25) Commercial Property Owners and Builders;

26) Computer and microcomputer systems and applications;

27) Military;

28) Aerospace;

29) Marine;

30) Agriculture;

31) Aquaculture;

32) Foreign and domestic;

33) Developing countries.



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