JP2933291B2 - Inverter device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

 [Object of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter for driving and controlling an electric motor.

[0002]

2. Description of the Related Art Three-phase induction motors (hereinafter referred to as motors).
Inverters are widely used because they can be easily controlled at a variable speed. However, the output frequency is set to 0 Hz, that is, free-run during operation due to a power failure or a user's emergency stop. That is.

Since the motor is rotating when the operation is restarted, when the motor starts from a normal starting frequency, a larger regenerative current flows as the difference between the rotating frequency of the motor and the frequency at the time of starting increases. Overvoltage trip may occur. For this reason, a method of detecting the rotation frequency from the induced voltage of the motor and starting from the starting frequency instead of the starting frequency is widely used.

[0004] When the motor is coasted during operation, an induced voltage having a frequency corresponding to the rotation speed of the motor is generated. An example of a conventional induced voltage detection circuit for detecting the induced voltage will be described with reference to FIG. In order to insulate this induced voltage from a control circuit (not shown), the voltage is dropped by a resistor 2 and a diode 3 by using an insulating transformer 1 and a comparator 4
Was used to shape and detect the waveform.

[0005]

However, when insulation is performed using a transformer as in the prior art, when the transformer 1 has a transformation ratio of 1: 1, a high voltage equivalent to that of the main circuit is applied to the control unit. To insulate by dropping the voltage with resistor 2,
It is necessary to secure the creepage distance at both ends of the resistor 2, and the occupied area on the substrate is increased. Also, if the transformer ratio is increased so that the creepage distance does not need to be secured,
The induced voltage generates an applied voltage immediately before the free run immediately after the free run. However, the applied voltage is rapidly attenuated, so that the detectable level becomes high and the detection becomes impossible immediately.

In view of the above, an object of the present invention is to provide an inverter device having a detection level equivalent to that in the case where the transformer transformation ratio is 1: 1 and occupying a relatively small area. . [Configuration of the Invention]

[0007]

In order to achieve the above object, the present invention has a plurality of switching elements, converts a DC power supply into an AC power supply having an arbitrary frequency, and converts the converted AC power supply into an electric motor. And an inverter means for supplying the same potential to the motor terminal for driving the upper switching element of each phase of the inverter means .
And drive means disposed on the substrate takes the creepage distance, this
Of these drive means, the same potential as the terminal of the motor
The electric motor of two adjacent drive means on a certain board
Detecting means for comparing an electric potential having the same electric potential with the terminal and detecting an induced voltage of the electric motor , wherein a power supply of a drive means on a reference side among the electric potentials compared by the detecting means is detected by the detecting means Provided is an inverter device used as a power supply for a vehicle.

[0008]

In the inverter device according to the present invention, the terminal of the drive means of the main element of the inverter means having the same potential as the terminal of the motor is used as a power supply for the comparison means for comparing respective potentials. By using the power supply of the driving means, the terminals of the motor and the terminals of the driving means are at the same potential, the terminals of the motor are on the driving means, and the driving means is connected between each phase of the inverter means and each phase with the other. Since the electronic equipment is insulated, the induced voltage of the electric motor can be accurately detected without providing any special insulating means (transformer), and the occupied area is relatively small.

[0009]

An embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the inverter device according to the present embodiment has a smoothing capacitor 11 for smoothing the DC power from a DC power supply 10 and the smoothed DC power from the smoothing capacitor 11 having an arbitrary frequency. A main circuit section A comprising a three-phase inverter circuit 13 for converting the AC power into the AC power and supplying the AC power to the motor 12, and drive circuits 14U, 14V, 14W, which drive the switching elements of each phase of the inverter circuit 13. 14XYZ, a control circuit 15 which outputs a control signal to the drive circuits 14U, 14V, 14W and 14XYZ to perform PWM control, a drive circuit 14U, 14V, 14W, 14XYZ and a control circuit 15
A photocoupler 16 for insulating the motor 12, an induced voltage detecting circuit 17 for detecting an induced voltage of the motor 12, and an inductive voltage detecting circuit 17 insulated to the same potential as that of the control circuit 15.
And a control unit B comprising a photocoupler 18 for sending the detected induced voltage to the control unit 5.

Further, as shown in FIG. 2, the induced voltage detecting circuit 17 compares a resistor 19 and a diode 20 having a voltage drop function with the U-phase and V-phase potentials to detect an induced voltage. 21. Further, the induced voltage detector circuit 17 is disposed on the substrate by utilizing the creepage distance of the driving circuit to consider the pre-designed creepage distance on the substrate required for insulation.

In this embodiment, the drive circuits 14U, 14V, 14W, 14
XYZ are insulated, and the emitter terminals are U, V,
Connected to W terminal.

Accordingly, by setting the same potential as that of the U-phase from the emitter terminal of the V-phase by the resistor 19 and the diode 20 for voltage drop, one end of the terminal of the resistor 19 is connected to the drive circuit 14V of the V-phase. The ends are included in the U-phase drive circuit 14U.

Then, the induced voltage of the motor 12 is detected by the comparator 21. As a result, the diode 13 and the comparator 21 also have a U-phase potential, and the power supply of the U-phase drive circuit 14U can be used as the power supply of the comparator 21.

As described above, according to the present embodiment, the induced voltage detecting circuit is formed by using a separate power supply insulated from the potential of the normal control circuit. Thus, the power supply of the U-phase drive circuit 14U can be used as the power supply of the comparator 21, and it is not necessary to newly prepare another power supply. Further, the insulation between U and V has already been performed by the drive circuits 14U and 14V, and there is no need to newly insulate them.

Therefore, one of both ends of the resistor 19 is connected to U
The other phase potential may be the V-phase potential, and the other components may be the U-phase potential. Further, the control circuit 15 and the comparator 21 are insulated from each other by the photocoupler 18, but this is also already insulated by the circuit for transmitting the PWM signal output from the control circuit 15 to the drive circuit, and is shown in FIG. like,
By disposing on the substrate, there is no need to prepare a new creepage distance. Further, since the induced voltage can be detected from the terminal of the motor, the problem of the detection level by the insulating transformer does not occur.

[0017]

As described above, according to the present invention,
It is possible to realize an inverter device having a detection means having a detection level of an induced voltage equal to or higher than that of the related art and having a relatively small occupied area, and the entire device can be downsized.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of the present invention.

FIG. 2 is a detailed configuration diagram showing an induced voltage detection circuit shown in FIG.

FIG. 3 is a circuit layout diagram showing a substrate layout to which an embodiment of the present invention is applied.

FIG. 4 is a schematic configuration diagram showing a conventional voltage detection circuit.

[Explanation of symbols]

10 DC power supply, 11 Smoothing capacitor, 12 Motor, 13 Three-phase inverter circuit, 14U, 14V, 14
W, 14XYZ: drive circuit, 15: control circuit, 1
6, 18 photocoupler, 17 induced voltage detection circuit, 19
... Resistor, 20 ... Diode, 21 ... Comparator

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H02P 5/408-5/412 H02P 7/628-7/632 H02P 21/00

Claims (1)

(57) [Claims] An inverter device for driving and controlling an electric motor.
An inverter having a plurality of switching elements, converting the DC power into an AC power having an arbitrary frequency, and supplying the converted AC power to the motor; and an upper switching element for each phase of the inverter. Has the same electric potential as the motor terminal that drives the creepage distance between each phase.
And drive means disposed on the substrate take away, these de
A substrate of the live means at the same potential as the motor terminal
Same as the motor terminals of the two adjacent drive means above
Comparing the potential with an electric potential, comprising a detecting means for detecting an induced voltage of the motor, the detecting means power in relation to the standard side of drive means of the potential to be compared by the detection means An inverter device used as a power supply.