JPH08196085A - Inverter - Google Patents

Abstract

PURPOSE: To obtain a same voltage from both three-phase and single phase power supplies by performing PWM control at a predetermined output voltage level in case of a three-phase input power supply whereas performing PWM control at a voltage level compensating for the DC voltage drop of a rectifier circuit in case of a single phase input power supply. CONSTITUTION: The potential difference across a coil 11 for driving a switch 10 is inputted to an input specification detector 7 and a decision is made whether the input power supply is three-phase or single phase based on the on/off state of an input switch 12. The decision result is delivered to a PWM control section 6. A DC voltage detection circuit 8 delivers a DC voltage value, converted through a rectifier circuit 1, 2, 3, to the PWM control section 6 where a reverse conversion circuit 4 is controlled to determine an output voltage to the load side. The PWM control section 6 selects a predetermined output voltage value according to an output frequency command received externally. In other words, a selected output voltage is employed in PWM control in case at three-phase input whereas the selected output voltage is corrected before being employed in PWM control in case of single phase input.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage type inverter device in which a three-phase induction motor is used as a load and the output voltage and frequency can be arbitrarily controlled by the load state and a command value from the outside.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram of a conventional voltage source inverter device when a power source is a three-phase alternating current, and similarly FIG. 4 is a block diagram when a power source is a single-phase alternating current. As shown in these figures, in the conventional inverter device, the diode module of the rectifier circuit and the number of wires are clearly divided according to the number of phases of the power source, and have different configurations depending on the number of phases of the power source. Regarding the output voltage control method, when the power supply is a three-phase AC, the DC voltage value obtained by the rectifier circuit of the inverter device in FIG. 3 is about 1.35 times the effective value of the power supply voltage, but the power supply is In the case of a single phase, it is about 1.22 times the power supply voltage, which is about 10% lower, so that the output voltage of the inverter is also lowered.

[0003]

The conventional inverter device has a different structure depending on the number of phases of the power source used.
Further, since the output voltage also varies depending on the number of phases of the power source, there is a problem that a difference occurs in the load current when operating with the same load. To solve this problem, conventionally, it has been necessary to separately design a motor connected to a load for the three-phase power supply and the single-phase power supply depending on the output voltage of the inverter device. In order to solve this problem, the present invention provides an input changeover switch capable of handling both three-phase and single-phase cases in the input part of the power supply and has a function of adjusting the output voltage according to the specifications of the input power supply. It is possible to realize an inverter device that can operate loads with the same characteristics regardless of whether the specifications are three-phase or single-phase.

[0004]

The inverter device of the present invention is provided with a switch capable of disconnecting the circuit in one phase of the wiring of the rectifying circuit section of the power input section, and a means for detecting the operation of the switch. The PWM control unit is adjusted so that the output voltage when the three-phase power supply is connected and the output voltage when the single-phase power supply is connected are the same.

[0005]

According to the present invention, when the input power source detected by the input specification detecting means is three-phase, PWM control is performed with a preset output voltage value, and when the power source is single-phase, the direct current obtained from the rectifier circuit is used. PWM control is performed with a voltage value that compensates for the voltage drop, and output voltage control is performed so that the same output voltage can be obtained for both three-phase and single-phase power supplies.

[0006]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an inverter device of the present invention. In FIG. 1, reference numerals 1, 2 and 3 denote a diode module, a power factor improving reactor, and an electrolytic capacitor that form a rectifying circuit, and this circuit converts a three-phase AC voltage into a DC voltage. Reference numeral 4 is a switching transistor module for inversely converting a DC voltage obtained from the rectifier circuit into an AC voltage, and 5 is a drive circuit for driving the transistor module. The transistor module and the drive circuit constitute an inverse conversion circuit. . Reference numeral 6 denotes a PWM control unit for generating a PWM signal for controlling the inverse conversion circuit, and in this embodiment, a signal can be inputted from the input specification detection device 7 and the DC voltage detection circuit 8. Reference numeral 9 denotes an input switching device, which is a switch 1 provided at a position where the T-phase can be separated from the three-phase AC input section in the preceding stage of the rectifier circuit.
0, a coil 11 for driving the switch 10, and an input switching switch 12 capable of controlling energization of the coil
It is possible to connect or disconnect the input phase T phase by turning on or off the input changeover switch 12 which is constituted by In the inverter device configured as in this embodiment, when the input selector switch 12 is turned on and the input section T-phase is connected to the rectifier circuit, the inverter device operates as an inverter device for inputting three-phase AC power, and the input selector switch is used. When 12 is turned off and the input part T-phase is disconnected from the rectifier circuit, it operates as an inverter device for inputting a single-phase AC power supply. Also, the input switching device 9
And other parts work as shown below. The potential difference between both ends of the coil 11 that drives the switch 10 in the input switching device is input to the input specification detecting device 7 and is input switching switch 12
Depending on the on / off state, the three-phase input state or the single-phase input state is detected by this potential difference.
The result is output to the PWM control unit. Further, the DC voltage detection circuit 8 PWMs the DC voltage value converted by the rectifier circuit.
Output to the control unit. A PWM circuit to which these signals are input controls the inverse conversion circuit to determine the output voltage to the load side.
The details of the method of controlling the output voltage in the PWM control unit are shown in FIG. The PWM control unit selects a preset output voltage value according to the output frequency command input from the outside.
In this embodiment, the number of phases of the input power supply is detected by the signal from the input specification detection device for the selected output voltage value, and in the case of three-phase input, the control is performed by the selected output voltage value and the single-phase input In this case, the selected output voltage value is corrected by the correction gain and controlled. This correction gain uses a value preset so that the output voltage when the input power supply has three phases and the output voltage when the input power supply has a single phase have the same value. Further, in the present embodiment, a signal from the DC voltage detection circuit is input to the PWM control unit, and even if the DC voltage fluctuates due to the fluctuation of the power supply voltage, the output voltage command is adjusted to keep the output voltage constant. . With the functions described above, the inverter device shown in this embodiment can keep the output voltage constant regardless of whether the power supply specifications are three-phase or single-phase. The same function is provided, and the input selector switch has a function of selecting either three-phase input or single-phase input.

FIG. 5 is a block diagram of control showing an embodiment of claim 2 of the present invention, and 13 is R-S, S of connected power sources.
The voltage between -T and T-R is measured. If the power is supplied to the three phases, the switch 12 is turned on to operate for three-phase power, and if the power supply voltage is supplied to only one phase, the switch 12 is used.
Is an automatic determination means of the number of power source phases that is turned off and operates for a single-phase power source. With this automatic determination function, it is possible to automate the switching operation of the connected power source by switching the switch described in claim 1.

[0008]

Since the inverter device of the present invention has the same operating characteristics with respect to the load by operating the input changeover switch regardless of whether the input power source is three-phase or single-phase, regardless of the number of power source phases on the user side. Functions as an inverter device.

[Brief description of drawings]

FIG. 1 is a control block diagram of an inverter device.

FIG. 2 is a control block diagram showing a voltage control method in the PWM control unit in the embodiment of the present invention.

FIG. 3 is a control block diagram of a conventional three-phase power input inverter device.

FIG. 4 is a control block diagram of a conventional single-phase power input inverter device.

FIG. 5 is a control block diagram of the inverter device according to claim 2;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Diode module, 2 ... Reactor for power factor improvement, 3 ... Electrolytic capacitor, 4 ... Transistor module, 5 ... Drive circuit, 6 ... PWM control part, 7 ... Input specification detection device, 8 ... DC voltage detection circuit, 9 ... Input switching device, 10 ... Switch, 11 ... Coil, 12 ... Input switching switch, 13 ... Automatic power phase number determination means.

Claims (1)

[Claims] 1. A rectifier circuit for converting a three-phase AC voltage into a DC voltage, an inverse converter circuit for converting a DC voltage obtained by the rectifier circuit into a three-phase AC voltage, and a PWM control unit for controlling the inverse converter circuit. In a transistor inverter including a switch, an input switching device including a switch capable of disconnecting a circuit in one phase of a three-phase input line in a front stage of a rectifying circuit, and a switching switch controlling ON / OFF of the switch, and the input switching device. An input specification detecting means capable of detecting an operation state of the device; and a PWM control section capable of inputting a detection result of the input specification detecting means and adjusting a voltage output from the inverse conversion circuit according to the result. An inverter device characterized by having.