1. Field of the Invention
The present invention relates to a fee calculation system for an electrical equipment and a method for the fee calculation, and especially to a fee calculation system for the electrical energy consumption of a motor drive and method for the fee calculation.
2. Description of Prior Art
Motor drives are used to control a rotation speed of a motor to be within a predetermined range. Therefore, the motor drive is also referred to as invertor. The motor drive can provide adjustable output power according to actual load, thus preventing power waste problem occurred in conventional fixed-speed motor. The motor drive has been extensively used for household usage such as air conditioner, refrigerator and microwave oven. The motor drive is more interested in industrial usage because the industrial usage will consume more electrical power.
The motor drive has energy saving function; nevertheless, user still cannot know the electrical energy consumption of the motor drive per se. With reference to
Moreover, the conventional motor drive has only display and input unit for display and input function; therefore, the conventional motor drive does not support calculation function to electrical energy consumption. It is desirable to provide value-added function to the motor drive without excessive cost increment.
The present invention provides a fee calculation system for electrical energy consumption of motor drive and method for the same.
Accordingly, the present invention provides a fee calculation system with a motor drive connected to a motor to obtain an output voltage, an output current and a power factor of the motor drive. The instantaneous load power of the motor is calculated based on above result and the total instantaneous consumption power is obtained by adding the internal power of the motor drive. The total instantaneous consumption power is then multiplied with the operation hour and the fee schedule input by user to obtain the total fee for the electrical energy consumption. The total fee is then shown on a display of the motor drive. Therefore, user can know the fee for operating a motor drive directly for a specific time period.
The features of the invention believed to be novel are set forth with particularity in the appended claims. The invention itself however may be best understood by reference to the following detailed description of the invention, which describes certain exemplary embodiments of the invention, taken in conjunction with the accompanying drawings in which:
With reference to
The instaneous load power P of a 3 phase (3 Φ) motor is
P=3×V×I×cosθ
where V stands for voltage, I stands for current, θ stands for power factor angle and cosθ stands for power factor.
Moreover, the instaneous load power for single phase is V×I×cosθ
With reference to
Afterward, the total instantaneous consumption power P is calculated (step 702), wherein the total instantaneous consumption power is the sum of the instantaneous load power Pout of the motor and the internal consumption power Pi of the motor drive. Namely, P=Pout+Pi.
The internal consumption power Pi of the motor drive accounts for the standby power consumption and the consumption power of power module. The standby power consumption is measured in a long-term base and the consumption power of power module is measured for various operation conditions.
The total instantaneous consumption power is converted to power consumption per hour Ph in step 703, namely, Ph=3600×P.
The total fee for the electrical energy consumption is then calculated (step 704), wherein the power consumption per hour Ph is multiplied with the operation hour T to obtain the total electrical energy consumption. Afterward, the total electrical energy consumption is multiplied with a fee schedule Ec input by user to obtain the total fee M for the electrical energy consumption. Namely, M=P×T×Ec, where T is operation hour of the motor drive in the unit of hour.
The above-mentioned fee calculation method can be implemented in the motor drive shown in
The controller 53 has a built-in program for performing the above-mentioned fee calculation method. The controller 53 obtains the electrical voltage V, the electrical current I and the power factor angle θ from the motor drive 5 to calculate the instaneous power Pout of the motor 4. Afterward, the fee schedule Ec and a particular time period are input through the input device 52. The controller 53 calculates the fee for the electrical energy consumption and then shows the calculated fee to the display 54.
According to above-mentioned method and system, the motor drive 5 can calculate the fee for the electrical energy consumption per se and shows the fee on the display 54 thereof. Moreover, the calculated fee can also be accessed or displayed remotely for further processing. Moreover, memory unit (not shown) can also be incorporated into the motor drive 5 to calculate an accumulative electrical energy and associated fee.
The above-mentioned motor drive 5 can calculate the consumed electrical energy and associated fee for the motor 4 and no additional measuring instrument is needed. Therefore, the wiring is simplified and the cost is reduced.
Although the present invention has been described with reference to the preferred embodiment thereof, it will be understood that the invention is not limited to the details thereof. Various substitutions and modifications have suggested in the foregoing description, and other will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims.