METHOD AND APPARATUS

FIELD OF THE INVENTION

[001] Embodiments of the present invention relate generally to Power Efficiency and more specifically to Adaptive Power Factor Control to automatically correct power factor to near unity.

BACKGROUND

[002] Electric motor power efficiency is of paramount importance. Everyone is increasingly interested in saving power, now that technology can make it possible and economy demands it. Advances in motor control algorithms and cost- effective electronic components for implementing motor drives are creating a revolution in virtually every electric motor market.

[003] Control of the power factor in an efficient manner also means less lost energy, both in the motor and drive electronics, and in the power grids supplying the electricity to the homes, offices, and factories where the motors are used.

[004] The potential energy savings are enormous. Over 40 million electric motors are used in manufacturing operations in the United States alone. Electric motors account for 65% to 70% of industrial electrical energy consumption and approximately 57 percent of all electrical energy consumption worldwide. Saving even a few percent of the world's 20 PetaWatt-hours (PWh) annual consumption of electricity yields several hundred Trillion Watt-hours per year, which represents well over a hundred billion dollars per year in savings.

[005] Currently, the average motor in use today has an efficiency of 88 percent in converting electrical into mechanical energy. Figures on the order of 96 to 98 percent conversion efficiency are achievable for big three phase motors.

[006] Power factor is critical for utility companies and their industrial, commercial and residential customers. They all have a desire to get the most cost effective electrical service for the end user's machinery. Low power factor means losses and penalty payments to the utility for consuming excessive reactive power.

[007] The rotating torque of an AC induction motor is created by an interaction between the active current component and the reactive current component (the magnetic field).

[008] Light load takes less active current but the magnetic field, and the reactive current, stays constant. This means that the power factor increases with increasing load, (see Figure 1). At full load, the current is mainly active but, at light loads, the current is mainly reactive.

[009] Low power factor also adversely affects the Utility's generating and transmission capacity. Figure 2 illustrates a table and a graph showing how the Power Factor varies with Load in various sizes of motors all operating at a constant speed, 1800 Hz.

[0010] Calculating Power Factor: The power factor triangle (Figure 1) illustrates how real power, reactive power and apparent power relate to each other to get the power factor angle. One way to get the power factor is by getting the cosine of the power factor angle.

[0011] A good analogy to illustrate Power Factor is a horse pulling a barge up the river. Pulling at an angle on the river bank requires much more work than if the horse were directly in front of the barge.

RealPower(kW) kW

Power r actor = = ,

Apparent Power(kVA) ^(kW) ² + (kVArf

[0012] There are some prior art AC Drives, referred to as Variable Frequency Drives (VFD) or Variable Speed Drives (VSD). They vary the speed of the motor to lower energy consumption. [0013] These VFD or VSD devices require a separate controller external to the motor. Most of these devices convert AC to DC and then back to AC again using an inverter.

[0014] There are a few Matrix or cycloconverter type AC drives appearing similar to the Matrix Variable Frequency Drive portion of the APFC System, but nothing exists that's fully integrated or innocuous clip-on to existing motors in a small highly integrated comprehensive solution like the APFC.

[0015] There are also some prior art VFD's, but nothing even close to this highly integrated comprehensive solution. See Figure 3 Prior Art in a VFD in a 6 in. x 24 in. x 36 in. box versus the APFC controller in Figure 7 which is 1 ½ inch x 3 in. x 4 in. which is 18 cubic inches versus 5,184 cubic inches. The VFD is 288 times larger and contains only a small portion of the functionality of the APFC.

[0016] Prior art power-factor-correction equipment utilizes capacitor banks and automation equipment to switch capacitor banks in an effort to help improve the power factor. The capacitors are large, bulky and expensive.

SUMMARY OF THE INVENTION

[0017] According to the main objectives provided herein, the teachings herein are directed to an Adaptive Power Factor Control System that automatically adjusts the speed of a motor to optimize load by sensing power factor and increasing power factor as close to unity as possible.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] It will be appreciated that the drawings are not necessarily to scale, with emphasis instead being placed on illustrating the various aspects and features of embodiments of the invention, in which:

[0019] Figure 1 : is a diagram showing Power Factor and Calculation [0020] Figure 2 is a graph showing Line Current and Power Factor versus Load on a 50 kW AC Induction Motor.

[0021] Figure 3 is a graph showing Typical Power Factor versus Load in various sizes of motors at 1800 Hz.

[0022] Figure 4 is a photograph of a Prior Art VFD in a 6 inch, x 24 inch, x 36 inch, space.

[0023] Figure 5 is a schematic drawing showing: Adaptive Power Factor Controller, Adaptive Load Balancing System 501 : Matrix Variable Frequency Drive Section 502: Sensors including Voltage, Current, Phase, Temperature Section; 503: Calculate Real-Time Power Factor using Microprocessor Section; 504:Closed Loop Adaptive Feedback Control Section

[0024] Figure 6 is a schematic drawing showing Matrix Variable Frequency Drive Section Based On AC-to-AC Conversion Topology.

[0025] Figure 7 is a schematic drawing showing Matrix PFC Module Assembly and Subassemblies. This module includes the 1200V IGBT or FET transistors, Microprocessor, Current Sensors, Voltage Sensors, Phase Sensors, Thermal Sensors, Heat Spreaders, Heat Sinks, and enclosure.

[0026] Figure 8 is a side view of a Fully Assembled Matrix PFC upgrade unit for mounted on a 5 HP Motor

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

[0027] Embodiments of the present invention are described below. It is, however, expressly noted that the present invention is not limited to these embodiments, but rather the intention is that modifications that are apparent to the person skilled in the art and equivalents thereof are also included.

[0028] The ADAPTIVE POWER FACTOR CONTROLLER (APFC) includes a built-in Matrix VFD. VFDs can be used to improve the power factor for manufacturers of drives and motors. VFD's may also improve process control, save electrical energy, and reduce machine wear. But the APFC adds another dimension in real-time adaptive control of power factor correction.

[0029] The APFC is an Adaptive Load Balancing System (see Fig. 5) continuously sensing, tracking and adjusting the motor speed to optimize power factor versus load and matches the input current to the output load using adaptive feedback control to drive the Matrix VFD in a servo like closed loop control. The motor is slowed down or sped up until it matches the load and optimizes the Power Factor, thus saving a significant amount of energy, sometimes 50% or more!

[0030] The APFC Adaptive Load Balancing System is small and innocuous. It may be easily retro-fitted onto existing motors, or integrated into new motors.

[0031] The APFC Adaptive Load Balancing System consists of a driving circuit having a power factor correction (PFC) function including a Matrix VFD power converter, a harmonic wave generator, a voltage divider, and a modify element. The power converter receives three phase AC input power and directly converts it to convert to 3 phase AC output power at variable frequencies. The harmonic wave generator generates a harmonic wave. The voltage level of the harmonic wave is decreased by the voltage divider to generate a comparing signal. Therefore the power factor (PF) of the driving circuit is enhanced.

[0032] A power-factor correction circuit for a three-phase power supply is provided. The correction circuit includes a filtering unit at the input receiving the three phases of the current, at least one inductor per phase placed downstream of the filtering unit, a rectifying bridge powering a current-chopping stage. The filtering unit may include a differential-mode filtering cell and may include one or more inductive circuits formed of a magnetic material in a double E, each leg of the E being surrounded by a winding.

[0033] One embodiment of the APFC is illustrated in Figure 5: Adaptive Power Factor Controller, Adaptive Load Balancing System which consists of four major blocks or sections driving the motor. [0034] The Matrix Variable Frequency Drive Section 501 , also referred to as an AC to AC Converter or "Cycloconverter" because it doesn't have an intermediate DC section for energy storage and no inverter is required to convert back to AC. The Matrix VFD receives nearly constant frequency (e.g. 50 Hz or 60 Hz) three phase AC input and generates variable frequency output on each of the three output phases by selecting various pick-off points on the three incoming phases and gating each pick- off point directly to one of the three output phases to effectively "synthesize" the output waveforms in real-time.

[0035] The Matrix VFD contains of a matrix of 9 switches connecting the three input phases to the three output phases directly as illustrated in Fig. 8. The controller has the capability to switch any input phase to any output phase at any time.

[0036] However, no two switches from the same phase are on at the same time to avoid short circuiting the input phases. The Matrix VFD is controlled via PWM in so, some embodiments to produce three phase variable voltages at variable frequencies.

[0037] The output frequency is adaptively controlled by the other sections working together sensing the power factor in real-time in an adaptive feedback control loop. Various embodiments of the Matrix VFD section use either IGBT drivers or Low RDS-ON High Voltage FET drivers.

[0038] The Sensors including Voltage, Current, Phase, Temperature Section 502. These sensors measure the voltage, current and the phase angles between voltage and current on each of the three phases and provides this information as well as thermal input to the Microprocessor in an adaptive feedback control loop.

[0039] The Real-Time Power Factor is calculated using Microprocessor Section 503. The adaptive controller firmware in the processor senses and optimizes the Power Factor by varying the frequency going out to the load, in order to maximize the Power Factor bringing it as close to unity as possible at all times; [0040] In Figure 1 and Figure 2, it is illustrated that the more the load, the greater the Power Factor at a given frequency [1800 Hz in this example]. However, by varying the frequency, the load may be increased, thereby increasing the Power Factor, while also saving energy.

[0041] The Closed Loop Adaptive Feedback Control Section 504. This section is adaptively varying the frequency going out to the load, in order to maximize the Power Factor bringing it as close to unity as possible at all times.

[0042] The invention may be embodied in other specific forms besides and beyond those described herein. The foregoing embodiments are therefore to be considered in all respects illustrative rather than limiting, and the scope of the invention is defined and limited only by the appended claims and their equivalents, rather than by the foregoing description.