CN204835502U - Converter main relay fail safe circuit - Google Patents

Abstract

The utility model discloses a failure protection circuit for a main relay of a frequency converter, which comprises a connector and an optocoupler. The connector is arranged at both ends of a start-up resistor. Pin 1 of the connector is connected in series with the first resistor to connect pin 1 of the optocoupler, and pin 2 is suspended in the air. , pin 3 is connected to pin 2 of the optocoupler; the first capacitor, the second resistor and the diode are connected between pin 1 and pin 2 of the optocoupler, pin 3 of the optocoupler is grounded, and the second capacitor is connected between pin 4 and pin 2 of the optocoupler Between ground, the third resistor is connected between pin 4 of the optocoupler and +24V, pin 4 of the optocoupler is connected in series with the fourth resistor and pin 3 of the dual diode is connected, and the fifth resistor is connected between pin 3 of the dual diode and the ground In between, pin 1 of the dual diode is connected to +3.3V, pin 2 of the dual diode is connected to the digital ground, pin 3 of the dual diode is connected in series with the sixth resistor and then connected to the CPU. The utility model prevents a large current from passing through the starting resistor by detecting the voltage at both ends of the starting resistor, protects the starting resistor from being burned, and does not cause malfunction, and has high sensitivity and rapid protection.

Description

Inverter main relay failure protection circuit

technical field

The utility model relates to the field of frequency converters, in particular to a failure protection circuit for a main relay of a frequency converter.

Background technique

The relay used by the frequency converter is connected in parallel at both ends of the starting resistor. During operation, if the relay fails and trips, the starting resistor will be burned. In the prior art, the auxiliary contact detection circuit of the main relay is mostly used to detect the working state of the main relay, and control the circuit on and off, so as to protect the starting resistor. However, the main relay auxiliary contact pull-in detection circuit is easy to cause misoperation, and the sensitivity is low.

Utility model content

In view of the above problems, the utility model provides a failure protection circuit for the main relay of the frequency converter, which can prevent the starting resistor from burning out by detecting the voltage at both ends of the starting resistor.

The technical scheme of the utility model is as follows:

A failure protection circuit for a main relay of an inverter, including a connector and an optocoupler, the connector is arranged at both ends of a starting resistor, and pin 1 of the connector is connected to pin 1 of the optocoupler after being connected in series with a first resistor, and the connector pin 2 of the optocoupler is suspended, pin 3 of the connector is connected to pin 2 of the optocoupler, the first capacitor, the second resistor and the diode are connected between pin 1 and pin 2 of the optocoupler, and pin 3 of the optocoupler ground, the second capacitor is connected between pin 4 of the optocoupler and the ground, the third resistor is connected between pin 4 of the optocoupler and +24V, and pin 4 of the optocoupler is connected in series with the fourth resistor Pin 3 of the dual diode, the fifth resistor is connected between pin 3 of the dual diode and ground, pin 1 of the dual diode is connected to +3.3V, pin 2 of the dual diode is connected to digital ground, and the dual diode The 3rd pin is connected to the CPU after connecting the sixth resistor in series.

The beneficial technical effect of the utility model is:

The utility model prevents a large current from passing through the starting resistor by detecting the voltage at both ends of the starting resistor, thereby preventing the starting resistor from being burned out. Compared with the existing main relay auxiliary contact pull-in detection circuit, the utility model can directly detect the working state of the main relay without causing malfunction, has high sensitivity and quick protection.

Description of drawings

Fig. 1 is the schematic circuit diagram of the utility model.

Detailed ways

Below in conjunction with accompanying drawing, the specific embodiment of the present utility model is described further.

As shown in Figure 1, the utility model includes a connector CN1 and an optocoupler PC1. The connector CN1 is arranged on both ends of the starting resistor R. Pin 1 of connector CN1 is connected in series with resistor R1 to pin 1 of optocoupler PC1, pin 2 of connector CN1 is suspended, and pin 3 of connector CN1 is connected to pin 2 of optocoupler PC1. Capacitor C1, second resistor R2 and diode D1 are connected between pin 1 and pin 2 of optocoupler PC1, pin 3 of optocoupler PC1 is grounded, capacitor C2 is connected between pin 4 of optocoupler PC1 and ground GND, resistor R3 Connect between pin 4 of optocoupler PC1 and +24V, pin 4 of optocoupler PC1 is connected in series with resistor R4 to pin 3 of dual diode D2. The resistor R5 is connected between pin 3 of the double diode D2 and the ground GND. Pin 1 of the dual diode D2 is connected to +3.3V, pin 2 of the dual diode D2 is connected to the digital ground DGND, and pin 3 of the dual diode D2 is connected to the CPU in series with a resistor R6.

The components and parts described above are all commercially available products, and the components and parts models in the embodiments can be found in the following table:

The main components list in Figure 1:

serial number Component code Component type Component parameters or models 1 CN1 Connector 2 PC1 optocoupler PC817 3 R1 resistance 3K, 3W, 5% 4 R2 resistance 10K, 1/10W, 1% 5 R3 resistance 22K, 1/10W, 1% 6 R4 resistance 27K, 1/10W, 1% 7 R5 resistance 3.9K, 1/4W, 1% 8 R6 resistance 10K, 1/10W, 1% 9 C1 capacitance 47uF,100V 10 C2 capacitance 220pF,50V 11 D1 diode RLS4148 12 D2 double diode DAN217U

The working process of the present utility model is as follows:

The starting resistor R (generally about a few ohms) is connected to the connector CN1, and the starting resistor R is connected in parallel with the relay. Under normal working conditions, the relay pulls in, the starting resistor R is short-circuited, the voltage of pin 1 and pin 2 of the connector CN1 is 0V, the optocoupler PC1 is not conducting, and the pin 4 of the optocoupler PC1 is in a high-impedance state, then the utility model The output of the circuit to the CPU is a high level. When the relay trips due to a fault, a voltage drop occurs at both ends of the starting resistor R. Through the buffer circuit of resistor R1 and capacitor C1, when the voltage and current of the input pin of optocoupler PC1 meet the conduction condition, the voltage of pin 4 of optocoupler PC1 is pulled down to GND (0V), then the output of the utility model circuit to the CPU is a low level, at this moment, the CPU blocks the SPWM signal output, turns off the IGBT, and the panel jumps to display a fault. The utility model prevents a large current from passing through the starting resistor R, that is, protects the starting resistor R from being burned.

Key points of the design scheme of the present utility model:

1. The starting resistor R is connected in series with the DC bus of the main circuit, which is a high-voltage circuit, and the optocoupler PC1 is used to isolate it, which protects the low-voltage circuit on the secondary side.

2. Anti-parallel diode D1 is connected to the input pin of optocoupler PC1 to absorb reverse voltage and prevent optocoupler PC1 from being broken down by back pressure.

3. The current limiting resistor R1 is packaged in 3W to meet the power requirements.

4. The voltage entering the CPU is clamped by diode D2, so that the voltage is between -0.6V～3.3+0.6V to protect the CPU.

5. The circuit of the utility model is made on the power board PCB, which occupies a small space and reduces the overall volume of the frequency converter.

The above are only preferred implementations of the utility model, and the utility model is not limited to the above examples. It can be understood that other improvements and changes directly derived or conceived by those skilled in the art without departing from the spirit and concept of the present utility model shall be considered to be included in the protection scope of the present utility model.

Claims (1)

1. A inverter main relay failure protection circuit, characterized in that it includes a connector (CN1) and an optocoupler (PC1), the connector (CN1) is arranged at both ends of the starting resistor, and the connector (CN1) Pin 1 of the first resistor (R1) is connected in series with pin 1 of the optocoupler (PC1), pin 2 of the connector (CN1) is suspended, and pin 3 of the connector (CN1) is connected to pin 2 of the optocoupler (PC1). pin, the first capacitor (C1), the second resistor (R2) and the diode (D1) are connected between pin 1 and pin 2 of the optocoupler (PC1), and pin 3 of the optocoupler (PC1) is grounded, The second capacitor (C2) is connected between the 4 pins of the optocoupler (PC1) and the ground, the third resistor (R3) is connected between the 4 pins of the optocoupler (PC1) and +24V, the optocoupler The 4 pins of the coupler (PC1) are connected in series with the fourth resistor (R4) to the 3 pins of the double diode (D2), and the fifth resistor (R5) is connected between the 3 pins of the double diode (D2) and the ground, the Pin 1 of the dual diode (D2) is connected to +3.3V, pin 2 of the dual diode (D2) is connected to digital ground, and pin 3 of the dual diode (D2) is connected in series with the sixth resistor (R6) to the CPU.