Inverter device for driving electric motor

Abstract

[PROBLEMS] An inverter for electric motor drive, suitable for an electric motor for fans and pumps and for en electric motor for driving motor vehicles. [MEANS FOR SOLVING PROBLEMS] An inverter device (4) for electric motor drive is constituted of two inverters, or an inverter (1) and an inverter (2), two electromagnetic contactors (43, 44), and one alternate operation control circuit (45). Usually, the inverter (1), the electromagnetic contactor (43) and the inverter (2), and the electromagnetic contactor (44) are alternately operated according to a command from the alternate operation control circuit (45) every time when a start switch (45a) and a stop switch (45b) are depressed, or alternatively, their operations are automatically alternated every 24 hours. As a result, their operation time periods are almost equal to each other, increasing operation reliability of the entire inverter device (5) and enabling power supply to an electric motor (3) to be continued even if either one fails.

Description

technical field [0001] The invention relates to an inverter device for driving a motor. The device generates AC power with variable voltage and frequency, and drives a motor with variable speed through the AC power, especially a motor that drives electric fans, pumps and the like. Background technique [0002] Figure 6 It is a circuit configuration diagram showing a conventional example of such an inverter device. In this figure, 1 is an AC power source such as a commercial power supply, 2 is an inverter device for driving a motor, and 3 is a motor such as an induction motor driven at a variable speed by the inverter device 2 for driving the motor. [0003] The inverter device 2 for driving a motor is composed of the following parts: the commercial power of a constant voltage and a constant frequency of the AC power supply 1 is converted into a ratio (V / f) of an output voltage V and a frequency f thereof which can be kept substantially constant. A general-purpose inverter ...

AI Technical Summary

Problems solved by technology

[0009] exist Image 6 In the shown conventional inverter device 2 for driving a motor, since only one set of general-purpose inverters 21 is provided, if any failure occurs in the inverter, it becomes the one for supplying the electric motor 3 with the electric power of the AC power source 1. state, as described above, there is a danger of changing the operating state of the motor load electric fan and pump

Moreover, after the general-purpose inverter 21 has been operated normally for a long time (for example, several years or more), if any failure occurs in the general-purpose inverter 21, when switching to the power supply from the AC power supply 1, There is a danger that the power supply from the AC power supply 1 cannot be switched due to malfunction due to welding of the contacts of the electromagnetic contactors 22 and 23, etc.

[0010] Moreover, as disclosed in the above-mentioned Patent Document 1, in a structure in which two sets of inverters, induction motors, and pumps are alternately operated for one water supply system, a larger installation space is required, and there are disadvantages of the device. The problem of higher overall prices

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