JPH1118470A - Inverter apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To calculate and indicate the output power of a motor or an inverter, without adding a special detector such as a DC current detector, etc. SOLUTION: In an inverter apparatus, the number of phases of an output current detected by a current transformer CT2 is converted by a 3-phase - 2-phase conversion circuit 23 for detecting a torque current component in a rated current. A power calculation circuit 32 calculates a motor output power from the detected torque current component, a motor revolution from a revolution detection circuit 11 and the rated capacity, circuit parameters and exciting current of a motor which are prepared in a memory 31, and the motor output power is displayed on a panel 37 surface via a display conversion circuit 35. By this method, it is not necessary to obtain the input power of the inverter as in the motor output power, so that a DC current detector, etc., becomes unnecessary.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device having a function of monitoring the output power of an inverter and the output power of a motor driven by the output power.

[0002]

2. Description of the Related Art In an inverter device, various variables used for control can be monitored on a panel surface or the like. FIG. 3 shows an example of the configuration of a voltage-source inverter device that performs current control and has a function of monitoring the power of the inverter and the motor.

[0003] In the figure, 1 is a forward converter for obtaining DC from a commercial power supply, 2 is a smoothing capacitor, 3 is a reverse converter for converting DC to AC, and drives an induction motor 5, and 4 controls an inverse converter 3. A vector control operation unit that calculates an output current command of the inverter to be operated.

[0004] The vector control operation unit 4 detects a set rotation speed, an excitation current setting, a motor rotation speed from the speed detection circuit 11, an inverter output current from the output current detection circuit 12, and a DC voltage detection from the DC voltage detection circuit 14. It takes in and calculates the output current command of the inverter.

A power calculation circuit 34 calculates the inverter output power and the motor output power from the DC current and the DC voltage from the DC current detection circuit 13 and the DC voltage detection circuit 14, and calculates the input power obtained by multiplying the DC current and the DC voltage. The inverter output power is obtained by subtracting the inverter loss, and the motor output power is obtained by subtracting the motor loss. Reference numeral 35 denotes a panel display circuit for displaying the output power of the inverter, the output power of the motor, and data of other monitor items on the panel 37 surface.

[0006]

In the conventional inverter device described above, a current detector CT1 and a voltage detector PD for detecting a DC current and a DC voltage are required to display power. Further, in order to obtain the output power of the motor, it is necessary to take a step of obtaining the output power of the inverter and then subtracting the loss of the motor, and the calculation is complicated.

SUMMARY OF THE INVENTION The present invention has been made in view of such conventional problems, and has as its object to reduce the output power of a motor or an inverter without attaching a special detector such as a DC current detector. An object of the present invention is to provide an inverter device which can calculate and display.

[0008]

SUMMARY OF THE INVENTION The present invention provides a speed detection circuit for detecting the number of revolutions of a motor driven by an inverter, an output current detection circuit for detecting an output current of the inverter, and a three-phase detection circuit. In an inverter device provided with a three-phase to two-phase conversion circuit that obtains a torque current component with respect to a rating by a two-phase conversion operation, the motor is determined based on the torque current detection component and the detected motor rotation speed, motor rated capacity, circuit constant, and excitation current. A motor output power calculation function for calculating the output power is provided, and the calculated power value can be monitored and displayed on a panel surface or the like as an absolute value or a comparison value.

[0009] Alternatively, the motor secondary power loss can be calculated based on the torque current detection component, the inverter output speed obtained by adding the slip of the motor to the motor speed, the rated capacity of the motor, the circuit constant, and the exciting current. Calculate the included power,
An inverter output power calculation function for calculating inverter output power by adding primary copper loss, mechanical loss, iron loss, and stray load loss to the motor is provided, and the calculated output power value is displayed as an absolute value or a ratio value on a panel. It is characterized in that monitor display can be performed on a surface or the like.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION

First Embodiment FIG. 1 shows a vector control block diagram of an inverter device according to a first embodiment. In the figure, reference numeral 16 denotes a deviation between the set rotation speed and the motor rotation speed from the speed detection circuit 11 as P.
A speed amplifier 17 for calculating I, a slip operation circuit 17 for calculating the slip rotation speed of the motor 5 from the torque current command from the speed amplifier 16 and the setting of the excitation current, and 20 a current control loop for vector control.

The current control loop 20 includes an adder 21 for adding a slip to the motor rotation speed to output the output rotation speed of the inverter, a frequency-phase conversion circuit 22 for converting the output rotation speed of the inverter to a phase (angular velocity). A three-phase to two-phase conversion circuit 23 for converting the output current from the output current detector CT2 into an exciting current component and a torque current component based on the rotational coordinates rotating in this phase, and the exciting current detected by the exciting current setting and phase conversion. Current control amplifier 25 for PI calculation of deviation from current
A current control amplifier 27 that performs PI calculation of a deviation between the torque current command from the speed amplifier 16 and the torque current detected by the phase conversion, and converts the excitation current and torque current from the amplifiers 25 and 27 into three-phase current commands. It is composed of a two-phase to three-phase conversion circuit for conversion.

Reference numeral 31 denotes known motor data such as the rated capacity, circuit constant, and exciting current of the motor 5; and 32, the known motor data, the torque current detected by the three-phase to two-phase conversion circuit 23, and the speed detection circuit 11. A motor power calculation circuit 35 for calculating the motor power from the motor rotation speed, etc., and a display 35 for converting the motor power calculated by the power calculation circuit 32 and the data of each monitor item input via the power calculation circuit into a panel-displayable form. A conversion circuit 37 is a panel for displaying these monitor items, and 38 is a D / A output circuit for outputting the motor power from the display conversion circuit 35 to the outside.

Generally, the output power Pout of the motor is obtained by the following equation. Pout = 1.027 × torque (kg · m) × rotational speed (rpm) On the other hand, the torque current component obtained by the three-phase to two-phase conversion of the vector control is a value proportional to the actual torque generated by the motor.

The power calculation circuit 32 calculates the output power Po of the motor.
ut is calculated by the following equation. Pout = coefficient × torque current detection × motor rotation speed This coefficient is calculated in advance from the known motor data 31.

The calculated motor output power Pout is displayed on the panel 37 via the display conversion circuit 35 together with other monitor items as one type of monitor item. Also,
The motor output power from the display conversion circuit 35 is externally analog-output via the D / A output circuit 38 and monitored.

Second Embodiment FIG. 2 shows a vector control block diagram of an inverter device according to a first embodiment. The difference from the one shown in FIG. 1 is that the power calculation circuit 32 in FIG. 1 calculates the output power of the motor 5, whereas the power calculation circuit 33 in FIG. Is calculated.
Therefore, the same components as those in FIG. 1 are denoted by the same reference numerals, and redundant description thereof will be omitted.

Hereinafter, the inverter output power calculation circuit 33 will be described. The power calculator 33 calculates the inverter output rotation speed (motor rotation speed + slip) from the adder 21 and the three-phase-2.
A configuration in which the power is obtained by multiplying the torque current detection value from the phase conversion circuit by a coefficient, and the primary copper loss, iron loss, mechanical loss, and stray load loss of the motor 5 are added to the value to calculate the inverter output power. Have been.

Generally, the output power Pin of the inverter (input power of the motor) is obtained by the following equation. Pin = Pout (motor output power) + secondary copper loss + primary copper loss + mechanical loss + stray load loss Pout = 1.027 × torque (kg · m) × (motor rotation speed + slip (rpm)). (Motor rotation speed + slip (rpm)) is always calculated by vector control.

On the other hand, the torque current component (torque current detection) obtained by the three-phase to two-phase conversion circuit 23 of the vector control is a value proportional to the actual torque generated by the motor IM.

The power calculation circuit 33 calculates the inverter output Pin by the following equation. Pin = coefficient × torque current detection × (motor rotation speed + slip (rpm)) + 1 primary copper loss + iron loss + mechanical loss + stray load loss This coefficient is calculated in advance from the known motor data 31. The primary copper loss is obtained from the primary current and the motor circuit constant, and the iron loss and the mechanical loss are (motor rotation speed + slip (rp)
m)) is calculated as a parameter. The stray load loss is calculated using (motor rotation speed + slip (rpm)) and a torque current component as parameters.

The calculated inverter output power Pin is displayed on the surface of the panel 37 via the display conversion circuit 35 together with other monitor items as one type of monitor item. Further, the motor output power from the display conversion circuit 35 is externally analog-output via the D / A output circuit 38 and monitored.

[0022]

Since the present invention is configured as described above, the following effects can be obtained.

(1) The power calculation can be performed only by a circuit of a detection system necessary for performing vector control without attaching a special detector such as a DC current detector for performing the power calculation.

(2) Since the power can be monitored by the inverter, the user can manage the power.

[Brief description of the drawings]

FIG. 1 is a vector control block diagram of an inverter device according to a first embodiment.

FIG. 2 is a vector control block diagram of the inverter device according to the second embodiment;

FIG. 3 is a block diagram showing a configuration of an inverter device according to a conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 forward conversion unit 3 reverse conversion unit 4 vector control calculation unit 5 induction motor 11 speed detection circuit 12 output current detection circuit 13 DC current detection circuit 14 DC voltage detection circuit 16 speed amplifier 17 slip Arithmetic circuit 20: current control loop 22: frequency-phase conversion circuit 23: three-phase to two-phase conversion circuit 25, 26: current control amplifier 28: two-phase to three-phase conversion circuit 31: known motor data such as motor capacity and constant 32, 33, 34 Power calculation circuit 35 Display conversion circuit 37 Display panel 38 D / A output circuit PD DC voltage detector CT1 DC current detector CT2 Output current detector PP Encoder R1 Charge limit Flow resistance S1: Resistance short-circuit switch MC: Electromagnetic switch.

Claims (3)

[Claims] 1. A speed detection circuit for detecting a rotation speed of a motor driven by an inverter, an output current detection circuit for detecting an output current of the inverter, and a three-phase-2
Obtain torque current component for rating by phase conversion calculation 3
An inverter device provided with a phase-two phase conversion circuit, comprising: a motor output power calculation function for calculating a motor output power from the torque current detection component, the detected motor speed, a motor rated capacity, a circuit constant, and an excitation current; An inverter device wherein the calculated power value can be monitored and displayed on a panel or the like as an absolute value or a comparison value. 2. A speed detection circuit for detecting a rotation speed of a motor driven by an inverter, an output current detection circuit for detecting an output current of the inverter, and a three-phase-2 output current.
Three phases to obtain torque current component for rating by phase calculation
In the inverter device including the two-phase conversion circuit, the motor output power is calculated from the torque current detection component, the inverter output rotation speed obtained by adding the slip of the motor to the motor rotation speed, the rated capacity of the motor, the circuit constant, and the excitation current. An inverter output power calculation function for calculating the power including the motor secondary copper loss and adding the motor primary copper loss, mechanical loss, iron loss and stray load loss to calculate the inverter output power; An inverter device characterized in that the output power value can be monitored and displayed on a panel surface or the like as an absolute value or a ratio value. 3. The inverter device according to claim 1, further comprising a D / A conversion function of outputting the calculated absolute value or ratio value of the electric power to the outside as an analog amount.