JPS61189178A - Regenerative resistor protecting device of inverter - Google Patents

Abstract

PURPOSE:To prevent a regenerative resistor from flowing a current at defective mode time and from burning by inserting a temperature fuse mechanism into a series circuit of the resistor and a regenerative transistor. CONSTITUTION:A 3-phase AC is converted into a DC by a rectifier of diodes D1-D6, and a 3-phase induction motor M is driven through an inverter of a capacitor C1 and transistors Tr1-Tr6. A regenerative device 1 is connected in parallel with the capacitor C1. The device 1 connects a capacitor C3 in paral lel with a protecting unit 2 and connects a series unit of a regenerative resistor R1 and a regenerative transistor Tr7 with the connecting point. This protecting device 2 is composed of a heater resistor R3 and a temperature fuse mechanism of a contact SW1 (normal-closed contact). Thus, when a transistor Tr7 is dam aged, an excess current is flowed to the device 2, the resistor R3 is heated to high temperature to open the contact SW1. The contact SW1 is not automati cally reset even if the temperature falls.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a protection circuit for a regeneration device of an inverter, and more particularly to a device that protects a regeneration resistor from burning out even if a short circuit mode occurs due to a failure of a regeneration transistor.

Conventional technology Conventionally, the regenerative resistance protection device for inverters was developed under the Japanese Patent Publication No. 58-1.
As is known from Japanese Patent No. 90291, it includes a circuit that measures the period during which current is flowing through the regenerative resistor, and a circuit that issues an alarm output when the measured value of the measuring circuit exceeds a predetermined value.

Problems to be Solved by the Invention However, in such a circuit, if the regeneration transistor fails and enters short-circuit mode, an alarm output will be issued and the motor will stop, but F2 will still remain. This provides a highly practical protection device at low cost.

Means to Solve the Problem The safety device of the present invention inserts a temperature fuse mechanism into the series circuit of the regenerative resistor and the regenerative transistor, so that the regenerative transistor malfunctions and enters short-circuit mode, resulting in loss of control. When this happens, the protection device operates and stops the power supply to the regenerative resistor to stop the burnout.

Embodiment Hereinafter, a protection device according to an embodiment of the present invention will be explained with reference to the drawings.

In the figure, diodes D1 to D6 are rectifiers that convert three-phase alternating current to direct current, and C1 is a capacitor.

M is a three-phase induction motor, and six transistors TT1.M are controlled by signals generated from a pulse width modulation circuit (not shown). ~T 4 e constitutes the Innoku Ichiba part.

1 is a regeneration device, which is connected in parallel with the capacitor C1. This regeneration device 1 has a capacitor C3 connected in parallel with the protection device 2, a regeneration resistor R1 connected to the interconnection point thereof, and a regeneration transistor T! 7 are connected to each value string.

Moreover, the protection device 2 is comprised of a series circuit of a heater resistor R3 and a contact 5W1 (normally closed contact).

Generally, in the case of a 0.75 kW electric motor, the regenerative resistor R1 uses a value of about 200 Ω, and when the regenerative transistor Tr7 becomes uncontrollable due to a failure and enters short-circuit mode, the power flowing through the regenerative resistor R1 is as follows. It becomes about 400W. However, general-purpose inverters on the market are designed with 100% efficiency in consideration of the operating conditions of general machinery, as well as small size and light weight.
A regenerative resistor of about 0W is often used.

Next, the operation will be explained based on one embodiment of the present invention.

Although not shown, the regeneration transistor Tr-r is connected to the regeneration of the motor M, detects the voltage of the capacitor C1, and turns on the regeneration transistor Tr-r: iFF
A unique base circuit is constructed.

The nursing device 2 is selected so that the temperature rise of the heater resistor R3 is low and the contact SW1 is "closed" with respect to the current flowing during normal operation related to regeneration of the electric motor M.

When the regenerative transistor T r 7 is damaged and enters the short-circuit mode, approximately 400 W of power is supplied to the regenerative resistor R1. At the same time, an excessive current flows through the protective device 2.
If the temperature rise of heater resistor R3 is high, contact SW1
opens. Note that this contact SW1 is connected to the heater resistor R.
3 is configured so that it does not automatically recover even if the temperature drops.

Note that this circuit is a DC high voltage circuit and is based on a small protection device, so a capacitor C3 inserted in parallel with the protection device 2 is required.

This is because when the contact SW1 is "open", an arc is connected under the above conditions, and the contact may be burnt out or welded, so the function of the capacitor C3 is to eliminate this arc connection.

As described above, the regenerative resistance of the inverter of the present invention can be constructed at low cost.

[Brief explanation of the drawing]

The figure is an electrical circuit diagram of a protection device in an embodiment of the present invention. D1-D6... Rectifier, C1-C3...
・Capacitor, 1... Regeneration device, 2...
・Protective device, R1...Regenerative resistance, Tr-r・
...Regeneration transistor, T r 1% T r
6... Drive circuit, M... Electric motor.

Claims (2)

[Claims] (1) A rectifier that converts alternating current to direct current, a drive circuit that supplies alternating current voltage to the motor using a pulse width modulated control signal, and a regenerative resistor for absorbing regenerative energy installed between the rectifier and the drive circuit. and a regeneration device having a series circuit including a regeneration transistor and a protection device, and the protection device is configured to cut off the current depending on the magnitude of the current flowing through the regeneration resistor when the regeneration transistor fails and enters a short circuit mode. A regenerative resistance protection device for inverters. (2) A regenerative resistance protection device for an inverter according to claim 1, which comprises a capacitor connected in parallel with the protection device.