Device for Measuring an Amount of Capacitance to Correct a Power Factor of a Running Electric Motor

Abstract

A device for measuring an amount of capacitance to correct a power factor of a running electric motor includes a three-phase bus for connection to the electric motor; a metering device operably connected to the three-phase bus for displaying KVAR, the metering device including a display for displaying power factor, voltage, current, frequency, active energy, reactive energy, active power, reactive power, apparent power or maximum demand of the motor; a plurality of switched delta-configured capacitor circuits operably connected to the three-phase bus, each of the switched delta-connected capacitor circuits having different capacitance values; and a plurality of switches, each of the switches being operably associated with a respective one of the switched delta-configured capacitor circuits to connect to the three-phase bus the respective one of the switched delta-connected capacitor circuit to minimize the KVAR reading.

Description

FIELD OF THE INVENTION

The invention pertains generally to individually measuring, in real-time, the actual operating conditions of an alternating current induction motor and in particular to a device for determining the capacitance required to optimally correct the power factor of electric motors.

BACKGROUND OF THE INVENTION

Electric motors are used in many aspects of everyday life. They are found in elevators, refrigerators, escalators, air exchange handlers, etc. Ideally, the efficiency ratio (or the PF) of the “work output” over the “energy consumed” by the electric motors should be 100%. In mathematical terms, 100% PF is expressed as:

$\frac{\begin{array}{c}1\mathrm{Kilowatt}\mathrm{of}\mathrm{Energy}\mathrm{Produced}\mathrm{by}\mathrm{the}\mathrm{Work}\\ \mathrm{Output}\mathrm{of}\mathrm{the}\mathrm{Electric}\mathrm{Motor}\end{array}}{\begin{array}{c}1\mathrm{Kilowatt}\mathrm{of}\mathrm{Energy}\mathrm{Consumed}\mathrm{by}\mathrm{the}\\ \mathrm{Electric}\mathrm{Motor}\end{array}}=100\%$

However, despite its prevalence and the developments in its manufacture, electric motors have always been inherently inefficient. In reality, electric motors have efficiency ratios of PF ranging from 40% to 70% for the very old class (legacy type), from 71% to 82% for the four to ten year-old class, and from 83% to 89% for the so-called “already efficient” class manufactured today.

The low PF is attributable to the time-delay between the running cycles of the electricity coming into the electric motors and the “inductive loads” connected to the electric motors. An electric motor operates by converting electricity into a magnetic field to produce work (e.g. compressing gas, pumping fluid, rotating a pulley, etc.). The amount of electricity or current required to produce the magnetic field is constant. However, when a load is connected to the electric motors, more current is needed to produce work to drive the load introduced. In other words, electric motors must keep up with the power demand of the load by consuming more electricity. In mathematical terms, it may be viewed as: amount of energy consumed>amount of energy produced. This additional consumption of electricity to produce the same amount of energy accounts for the low PF in electric motors.

Although the low PF is inherent in all electric motors, the rate of efficiency is determinable, predictable, measurable, and controllable. Hence, such rate is capable of being optimized to near 100% PF. Near 100% PF can be achieved by simply installing customized “compensator capacitor(s)” that can store and deliver the deficient current to the electric motors. Installation of this compensator capacitor is a relatively simple task. The difficulty lies in the determination of the capacitance value (the amount of energy that a capacitor stores) of the compensator capacitor.

At present, the determination of the capacitance value is made by monitoring, collecting data from, the electric motors using at least three (3) multi-meter testers, while such runs for an extended period of time. The information derived is utilized in manually computing for and determining the required capacitance value. This method is prone to error because of the inaccuracies of the monitoring devices and the intrinsic deviations involved in deriving the values. Furthermore, the task is laborious and complicated, as it requires multiple devices (therefore, multiple operators) just for the task of monitoring.

SUMMARY OF THE INVENTION

The MAPS-CAPCU (the “System”) provides a simple, accurate, complete, and mathematically precise way of individually measuring, in real-time, the actual operating conditions of an alternating current induction motor (the “electric motor”). The System measures the power quality of individual inductive loads in order to determine, at virtually zero percent (0%) error, the exact capacitance required to optimally correct the power factor (“PF”) of electric motors: thereby, improving power consumption, reducing energy wastage, and improving the power output of the motor. The System is capable of mapping all since phase electric motors with power rating of up to 75 Horsepower (“HP”); and three phase motors with power rating between 5 HP and 600 HP.

Those difficulties encountered in the prior art are addressed by the System through the following:

First, the System achieves 100% or near 100% accuracy in measuring or “mapping” the values relative to the performance of electric motors by using combinations of several capacitors of different capacitance values connected in groups. The actual method of measuring the values needed to determine the exact capacitance value to optimize the PF is achieved by pushing one or a combination of any of the seven push-button switches to the System. Thereafter, when the desired PF is achieved, the values required to calculate the required capacitance value are shown in the digital display of the system.

Second, the System is complete and compact. Compared to the present system of measurement, the System only requires one person for operation. Furthermore, measurement is done instantaneously without need for prolonged monitoring; thereby, an on-the-spot, real-time map of the electric motor's performance is provided without need for prolonged data gathering and manual computation.

The summary above only gives a general background of the invention. The detailed description of the invention and the claims should be read together with the attached drawings in order for there to be full understanding of the invention. Hereafter, identical reference numerals refer to identical or similar parts.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings are attached to this description:

FIG. 1 is an isometric view of the present invention;

FIG. 2 is the front view of the front panel of the invention; and

FIG. 3 is a schematic diagram of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

There is shown in FIG. 1 a MAPS-CAPCU device 21 encased in a rectangular hermetically-sealed NEMA 3R Indoor/Outdoor steel case A. Steel case A is built from bio-safe materials suitable for use in non-hazardous locations with a flash point of +182° C. to 200° C. Steel case A is resistant to ingress of water, rain, sleet, snow, gasoline, and oil. MAPS-CAPCU device 21 is equipped with front panel 22 that houses all of the controls necessary to operate the invention.

In FIG. 2, it is shown that the front panel 22 houses the following: (1) metering device B; (2) power factor correction module C; (3) first three phase lead D; (4) second three phase lead E; (5) third three phase lead F; (6) ground lead G; (7) voltage selector H; (8) push-button switches I; (9) auto-hunting push-button J; and (10) pilot lights K.

Metering device B and power factor correction module C are both four-digit digital output devices that display power factor, voltage, current, frequency, active and reactive energy, active and reactive power, apparent power, and maximum demand.

Push-button switches I and auto-hunting push-button J are electrically connected to pilot lights K as indicators if the corresponding push-button is closed or open. Push-button switches I may be pushed to any of the 128 possible combinations in order to accurately calculate the required capacitance to optimize the PF in the 99% to 100% range. Auto-hunting push-button J may be pushed to by-pass all push-button switches I and automatically calculate the required capacitance to optimize the PF in the 99% to 100% range.

First three phase lead D, second three phase lead E, and third three phase lead F electrically connect to lead wires that are in turn attached to the electric motors being mapped. For single phase electric motors, only first three phase lead D, second three phase lead E, and ground lead G are used to connect to the motor. For three phase electric motors, first three phase lead D, second three phase lead E, third three phase lead F, and ground lead are used to connect to the electric motor.

FIG. 3 is a schematic diagram of the sizing unit of MAPS-CAPCU device 21 being used with metering device B and power factor correction module C to determine the values needed to optimize the PF. The sizing unit of MAPS-CAPCU device 21 is composed of a plurality of capacitor circuits L electronically connected to first phase bus N, second phase bus O, and third phase bus P. In turn, first phase bus N, second phase bus O, and third phase bus P, are electronically connected to first phase lead D, second three phase lead E, and third three phase lead F, respectively.

Each capacitor circuit L is mainly composed of a push-button switch I and 3 electronically-connected delta-configured capacitors S. Each delta-connected capacitors S may be activated by pushing the corresponding push-button switch I in order to accurately measure the correct amount of capacitance needed to optimize the PF in the 99% to 100% range. When any or a number of push-button switches are closed or opened, the corresponding pilot lights K shall turn on or off. Each connection of every delta-connected capacitors S to its corresponding capacitor circuit L is interrupted by a circuit breaker M, which is, in turn, electronically connected to the corresponding push-button switch F. Circuit breaker M provides a certain degree of short circuit and thermal overload protection of the capacitor components.

Each of the two poles of push-buttons I is electrically connected to one of the two 220-Volt poles of transformer R and also electrically connected to one pole of jumper terminal Q. Each one of the two 440-Volt poles of transformer R is likewise electrically connected to one pole of jumper terminal Q. The other pole of jumper terminal Q on the 220-Volt and 440-Volt side of the transformer R is electrically connected to second phase bus O, while the other pole of jumper terminal Q on the 220-Volt and 440-Volt side of transformer R is electrically connected to third phase bus P.

Claims

1. A device for measuring an amount of capacitance to correct a power factor of a running electric motor, comprising: a three-phase bus for connection to the electric motor;a metering device operably connected to said three-phase bus, said metering device including a display for displaying power factor, voltage, current, frequency, active energy, reactive energy, active power, reactive power, apparent power or maximum demand of the motor;a plurality of delta-configured capacitor circuits operably connected to said three-phase bus, each of said switched delta-connected capacitor circuits having different capacitance values; anda plurality of switches, each of said switches being operably associated with a respective one of said delta-configured capacitor circuits to connect to said three-phase bus said respective one of said delta-connected capacitor circuit to improve the power factor of the electric motor.

2. A device as in claim 1, wherein: said device includes a housing with a front panel; andsaid display is disposed on said front panel.

3. A device as in claim 1, wherein said housing is a rectangular hermetically-sealed NEMA 3R Indoor/Outdoor steel case.

4. A device as in claim 1, wherein said plurality of switches include respective pilot lights.

5. A device as in claim 1, wherein each of said delta-configured capacitor circuit includes three equal value capacitors.

6. A device as in claim 5, wherein said delta-configured capacitor circuits comprises 7 capacitor circuits with capacitors with the following capacitance values: C1=6 μF, C2=15 μF, C3=30 μF, C4=60 μF, C5=60 μF, C6=60 μF, and C7=70 μF.