JPH03190582A - Inverter unit - Google Patents

Abstract

PURPOSE:To reduce the size and the weight of an inverter unit by employing a part or the entirety of the inverter, for converting AC current through a power rectifier into DC current and then inverting the DC current through a power inverter into AC current, as a chopper controller for recovery power control. CONSTITUTION:When a motor 10 is accelerated, a circuit breaker 2 is closed and an acceleration/brake switching contactor 4 short-circuits a recovery power processing resistor 5 thus separating a circulation diode 6. Gates of a power rectifier 3 and a power inverter 9 are then turned ON thus generating VVVF. When brake is applied, gates of the power rectifier 3 and the power inverter 9 are turned OFF and the circuit breaker 2 is opened to switch the contactor 4 thus connecting the diode 6 and releasing short circuit of a resistor 5. The gates of the power inverter 9 and the power rectifier 3 are then turned ON. The power rectifier 3 is subjected to PWM control in order to control current flow through the resistor 5. By such arrangement, a part or the entirety of the power rectifier 3 is employed for chopper control and availability of facility is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inverter device for driving an electric motor, and relates to a method of processing regenerated power of the electric motor with a resistor to obtain stable braking force.

[Conventional technology]

When an electric motor is driven by an inverter device, when braking is applied to slow down or stop the electric motor, electric power is regenerated from the electric motor to the inverter device.

At this time, unless the forward converter is operated regeneratively to regenerate power to the power source or consumed as heat energy by a resistor within the inverter, the DC voltage within the inverter will rise and braking will not be possible.

Depending on the system, regeneration of power to the power source may not be permitted, and if braking is required even in the event of a power outage in the system, a resistor for regenerative power processing is required.

FIG. 2 is a diagram showing a conventional inverter device.

To accelerate the electric motor (10), close the AC breaker (2), and use a self-excited forward converter consisting of a forward converter arm (3) consisting of a GTO and parallel diodes, a main smoothing reactor (7), and a smoothing capacitor. (8) supplies DC voltage to the voltage type three-phase inverter (9). Inverse converter (9)
supplies AC power to the motor (10) based on this DC voltage.

Next, in order to brake the electric motor (10), the gate signal of the forward converter arm (3) is cut off, and the chopper arm (10) is cut off.
By igniting 1), the regenerative power processing resistor (5
) consumes regenerative power.

At this time, the firing pulse of the chopper is connected to the smoothing capacitor (8).
PWM control is performed so that the terminal voltage of is kept constant.

[Problem to be solved by the invention]

The above conventional technology requires a dedicated chopper arm (11) and chopper smoothing reactor (12) to apply regenerative braking, and if the braking time is shorter than the acceleration and constant speed operation time of the electric motor, , there was a problem of low utilization rate of equipment.

An object of the present invention is to relate to an inverter device having a small number of parts, high reliability, and having a regenerative braking function.

[Means to solve the problem]

In order to achieve the above object, the arm of the forward converter is used as a chopper arm for regeneration control during first regenerative braking.

[Effect]

The forward converter arm operates as a chopper arm during regenerative braking. This eliminates the need to prepare an arm dedicated to the chopper, and also eliminates the need for a smooth reactor dedicated to the chopper.

〔Example〕

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

This system uses a voltage source three-phase inverse converter (diode and GTO
(composed of a forward converter arm (3) consisting of a forward converter arm (3)).

Main smoothing reactor (7), smoothing capacitor (8).

Voltage type three-phase inverse converter (9), regenerative power processing resistor (5), and chopper freewheeling diode (6).

Consists of a contactor (4) for acceleration/braking switching.

AC breaker (2) to accelerate the load motor (10)
is closed, the regenerative power processing resistor (5) is short-circuited using the acceleration/braking switching contactor (4), and the freewheeling diode is cut off.

After this, the gate of the forward converter is turned on, and then the gate of the inverse converter is turned on. Note that the forward converter is PWM controlled so that the terminal voltage of the smoothing capacitor (8) is constant.

To apply braking, open the AC breaker (2) after turning off the gate pulses of the forward converter and inverse converter, and connect the chopper freewheeling diode (6) using the acceleration/braking switching contactor (8). Then, stop shorting the regenerative power processing resistor (5). Thereafter, the gate pulses of the voltage type three-phase inverse converter (9) and the forward converter arm (3) are turned on.

When the voltage of the smoothing capacitor (8) increases due to the regenerative operation of the inverse converter, the gate pulse of the forward converter arm (3) is subjected to PWM control to control the current flowing to the regenerative power processing resistor (5). Due to this.

The terminal voltage of the smoothing capacitor (8) is controlled to be constant.

This allows stable braking.

Note that during regeneration, the entire three pairs of forward converter arms (3) can be operated as a chopper, or only one pair of arms can be operated as a chopper, and the other two pairs of arms can be always turned off.

〔Effect of the invention〕

According to the present invention, since the arm for the forward converter can be used for chopper control of regenerative braking, there is no need for power semiconductors, gate amplifiers, etc. exclusively for the chopper, which improves the utilization rate of equipment and makes the device smaller and lighter. It has the effect of

Furthermore, since the single circuit configuration is simplified, there is also the effect of improving reliability.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example in which a converter element is substituted for the chopper element for processing the first regenerative power in one embodiment of the present invention;
FIG. 2 shows an example of the prior art, in which a chopper element is used in addition to the converter element. 1... 3-phase AC power supply, 2... AC breaker, 3...
・Arm for forward converter, 4... Contactor for acceleration/braking switching, 5... Resistor for regenerative power processing, 6... Freewheeling diode for chopper, 7... Main smoothing reactor, 8...
Smoothing capacitor, 9... Voltage type three-phase inverse converter, 10.
...Load motor, 11...Chopper arm, 12.
...Smooth reactor for chopper.

Claims (1)

[Scope of Claims] 1. A motor consisting of a self-excited semiconductor forward converter that obtains DC power from an AC power source, a DC smoothing filter capacitor, a self-excited semiconductor inverse converter, and a resistor for processing regenerative power during motor braking. An inverter device for driving, characterized in that the inverter device is provided with a function of using part or all of the forward converter as a chopper controller for controlling regenerative power. 2. In the inverter device according to claim 1,
The regenerated power is usually returned to the AC power source via a forward converter,
An inverter device that consumes regenerated power as thermal energy via the chopper controller when an AC power source has a voltage drop or a power outage.