JPH02269480A - Protecting device for inverter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a protection device for inverter power supply phase loss.

(Prior art) Conventionally, in inverters, for example,
As disclosed in the publication, a smoothing circuit having a smoothing capacitor is provided between the forward conversion circuit and the inverse conversion circuit, and when the power is turned on, the smoothing capacitor suppresses inrush current and the forward conversion circuit This prevents the destruction of

(Problem to be Solved by the Invention) However, with the above conventional system, even if one phase is open in the connection between the inverter and the three-phase power source, the inverter operates in a single phase once the power is turned on. After that, it will trip due to the undervoltage caused by the phase loss and stop abnormally.

The present invention has been made in view of the above points, and its purpose is to reduce the number of additional equipment required and to take measures against power supply phase loss at a low cost. The aim is to prevent the inverter from abnormally stopping due to undervoltage by prohibiting this in advance.

(Means for Solving the Problems) In order to achieve the above object, the present invention takes measures against power supply phase loss by utilizing the internal power supply section of the inverter and the above-mentioned smoothing capacitor.

In other words, the specific solution of the present invention is as shown in FIGS. 1 and 2. Assuming a protection device against phase loss, the internal power supply unit (20) that serves as the operating power source for the internal equipment of the inverter (3) is connected to two predetermined phases (for example, R phase and S phase) of the three-phase power supply (1). It is configured to receive power supply, and also has a three-phase power supply (1
A smoothing capacitor (C1) is connected between the remaining one phase (T phase) of ) and one phase (for example, S phase) of the above two predetermined phases,
A voltage detection section (30) is provided to detect the terminal voltage of the smoothing capacitor (C1), and when the terminal voltage of the smoothing capacitor (CI) detected by the voltage detection section (30) is less than a set value, inverse conversion is performed. A control inhibiting section (40) for prohibiting control of the circuit section (6) is provided.

(Function) With the above configuration, in the present invention, when the R phase or S phase of the three-phase power supply (1) has an open phase, the internal power supply section (20) does not supply power to the internal equipment. Inverse conversion circuit section (
Since the control 6) is not performed and the inverter (3) does not operate originally, it is possible to reliably prevent the inverter (3) from tripping and stopping due to the open phase of the R phase or the S phase.

In addition, when the T phase is out of phase, the internal power supply section (20) operates normally and the inverse conversion circuit section (6) is controlled and sold, but the smoothing capacitor (CI) between the R phase and the T phase
Since the terminal voltage of the inverter (6) is lower than the normal value, the control of the inverse conversion circuit section (6) is prohibited by the control prohibition section (40), thereby ensuring that the trip stop caused by the phase loss of the inverter (6) is prevented. It can be prevented.

In this case, if the control prohibition unit (40) displays the T-phase power supply open phase, the T-phase open phase can be easily confirmed.

In this case, as a countermeasure against power supply phase loss, the only additional equipment to be added is the voltage detection section (30) and the control prohibition section (40), so that the power supply phase loss can be countermeasured at a low cost.

(Effects of the Invention) As explained above, according to the inverter protection device of the present invention, it becomes impossible to supply power from the inverter's internal power supply section to internal devices in the event of a predetermined two-phase open phase. Since the remaining open phase of one phase is detected by the terminal voltage of the smoothing capacitor, it is possible to reduce the number of additional equipment and prevent the inverter from starting to operate on a single phase in the event of a power supply open phase. This can reliably prevent the inverter from tripping and stopping due to undervoltage.

In this case, when a predetermined phase open phase is detected due to insufficient terminal voltage of the smoothing capacitor, this predetermined phase open phase can be easily confirmed by displaying the predetermined phase open phase.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a control circuit for a refrigeration system that controls the capacity of a compressor using an inverter. In the figure, (1) is a three-phase power supply, (2) is an outdoor control board provided in the outdoor unit, (
3) is an inverter. The inverter (3) includes a diode module (5) as a forward conversion circuit, a transistor module (6) as an inverse conversion circuit section that converts the power supply frequency to another frequency, and the outdoor control board (2). ) and pulse width modulation ('PWM) the transistor module (6).
The PWM signal of the microcomputer (7) is output to the transistor module (6) through a waveform synthesis circuit (9), a phase-sequence switching circuit (10), and a driver (11). be done.

In the inverter (3), the diode module (5) is connected to the R phase of the three-phase power supply via the three wires (15).
In addition to being connected to the S phase and T phase, the transistor module (6) is also equipped with a relay (M
C) is connected. In addition, the diode module (
The R-phase and S-phase terminals of 5) are connected to wiring (16) and (
1B) to the transistor module (6).

Inside the inverter (3) is the microcomputer (
A DC-DC converter (20) is provided as an internal power supply section of a built-in device such as
20) is the predetermined two phases (R in the figure) of the three-phase power supply (1).
phase and S phase) with wiring (21) and (21).

Wires (16) and (1B) connected to the R-phase and T-phase terminals of the diode module (5), that is, the D
An unexpected connection was made to the C-DC converter (20).

The remaining one phase (that is, T phase) and the predetermined two phases to be connected (R
A smoothing capacitor (CI) and a resistor (R2) are connected between the − phase (R phase in the figure) of the phase and S phase).

In addition, the above three-phase power supply (1) and diode module (5)
), the three wires (15) that connect the relay (52
C) three normally open contacts (52G-1) are interposed, and the relays (52C) are activated by the closing operation of the normally open contacts (3x) controlled by the microcomputer (7). ON works.

Furthermore, the R-phase and S-phase open wiring (15), (15
) is the normally open contact (52C-1) of the relay (52C).
, (52C-1) and other wiring (23) in parallel with (52C-1)
2() is connected, and a current limiting resistor (R1) is interposed in this R-phase open wiring (23). In addition, each wiring (23
), (23) have normally open contacts (84), (84)
is interposed.

In addition, the inverter (3) includes a voltage detection section (30) that detects the terminal voltage of the smoothing capacitor (CI) based on the terminal voltage of the resistor (R2) connected in parallel with the smoothing capacitor (C1). At the same time, the terminal voltage signal of the smoothing capacitor (C1) detected by the voltage detection section (30) is input to the protection circuit (31).

The protection circuit (3I) has a function of comparing the terminal voltage of the smoothing capacitor (C1) with the terminal voltage under normal conditions without power supply phase loss, and determines that an undervoltage occurs when the voltage is less than the normal value. is the latch circuit (35) and the abnormality processing circuit (3B
) to the microcomputer (7), and the microcomputer (7) displays the four services on the display section (37) when the undervoltage determination signal from the protection circuit (al>bl, etc.) is input. It has a function to display a code indicating undervoltage on the monitors (Dl) to (D4).

Next, the control performed by the microcomputer (7) at power-on will be explained based on the control flow shown in FIG. 2.

After the start, it is determined in step S1 whether or not there is a command to operate the compressor. If there is a command to operate the compressor, the normally open contacts (84) and (84) of the relay are controlled ON (closed) in step S2, and the timer is turned on in step S3. Start TMI (eg 5 seconds). As a result, current flows from the R phase and S phase of the three-phase power supply (1) to the diode module (5) via the current limiting resistor (R1). At this time, the diode module (
5) The increase in terminal voltage is suppressed by the smoothing capacitor (C1).

Then, in step S4, it is determined whether or not an undervoltage judgment signal has been received from the protection circuit (31), and when the undervoltage is being received, it is determined in step S5 whether or not the timer TMI has timed up, and if NO is If the time is up, the process returns to step S4, but if the time has elapsed, it is determined in step S6 that the voltage is undervoltage, and the P of the transistor module (6) is
WM control is not performed, and a code indicating that there is an undervoltage is displayed on the four service monitors (old) to (D4) of the display section (37).

On the other hand, if it is determined that there is no undervoltage in step S4, a timer TM2 (for example, 2 seconds) is started in step S7, and if TM2 times out in step S8, the normally open contact (84 )
, After controlling (84) to 0FF (open), step SI
Start timer TM3 (for example, 20txsec) at O, and if 7M3 times up at step Sll,
It is determined that no current flows through the normally open contacts <84) and (84), and the normally open contacts (3x) are closed for the first time in step SI2 to turn on the relay (52C). For the first time, a transition is made to the normal operation mode based on the frequency command signal from the outdoor control board (2).

Therefore, steps 84 to S6 of the control flow in FIG.
Therefore, when the terminal voltage of the smoothing capacitor (C1) detected by the voltage detection section (30) is less than the set value, PWM control of the transistor module (6) by the microcomputer (7) is prohibited, and the display section (37 )
A control inhibiting unit (40) is configured to display an open phase of the T-phase power supply on the four service monitors (DI) to (D4).

Therefore, in the above embodiment, the inverter (3)
In the case where the R phase or the S phase is open, even if there is an operation command, the DC-DC converter (20) does not receive power from the three-phase power supply (1), so the DC-DC converter (20) Since R does not supply power to the microcomputer (7) and the microcomputer (7) is inoperable, the transistor module (6) is not PWM controlled and the inverter (3) remains in a stopped state. When the phase or S phase is open, the inverter (3)
During the installation, if the refrigeration system is trial operated, the phase loss can be easily confirmed, so that trip stoppage of the inverter (3) caused by the phase loss of the R phase or the S phase can be eliminated.

In addition, in the case of an open phase of the T phase, the DC-DC converter (
20) receives power supply, the microcomputer (7) is in a situation where it can perform PWM control on the transistor module (6). However, since the terminal voltage of the smoothing capacitor (C1) is less than the normal value, the microcomputer (7) receives an undervoltage judgment signal from the protection circuit (31) and controls the transistor module ( 6) is prohibited from PWM control. As a result, the inverter (3) maintains the stopped state in the same way as described above, so that the trip stop of the inverter (3) after installation due to an open phase can be eliminated. Moreover, in this case, T
If a phase is open, the service monitor jDl) on the display section (37)
(D4), so the open phase of the T phase can be easily confirmed.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is an electric circuit diagram and a flowchart showing control at the time of a second crystal transition command. (1)...Three-phase power supply, (3)...Inverter, (6
)...Transistor module (inverse conversion circuit section),
(7)...Microcomputer, (C1)...Smoothing capacitor, (R1)...Current limiting resistor, (R2)...
・Resistance, (20)...DC-DC converter (internal power supply section'), (30)...Voltage detection section, (31)...
- Protection circuit, (37)...display section, (40)...control prohibition section. (1)...Three-phase power supply (3)...Inverter (6)...Transistor module (inverse conversion circuit section)
(7)...Microcomputer (C1)...Smoothing capacitor (R1)...Current limiting resistor (R2)...Resistor (20)...DC-DC converter (internal power supply section) (
30) Voltage detection section (31) Protection circuit (37) Display section (40) Control prohibition section Fig.

Claims (2)

[Claims] (1) A protection device against power supply phase failure of an inverter (3) connected to a three-phase power supply (1) and converting the power supply frequency to another frequency, which Connected between the internal power supply section (20) that receives power supply and serves as the operating power source for the internal equipment of the inverter (3), the remaining one phase of the three-phase power supply (1), and one phase of the above prescribed two phases. the smoothing capacitor (C1), the voltage detection unit (30) that detects the terminal voltage of the smoothing capacitor (C1), and the terminal voltage of the smoothing capacitor (C1) detected by the voltage detection unit (30) set value. An inverter protection device characterized by comprising a control prohibition section (40) that prohibits control of the inverse conversion circuit section (6) when the inverter is less than or equal to the maximum value. (2) The inverter protection device according to claim 1, wherein the control inhibiting section has a function of displaying a power supply phase failure when the terminal voltage of the smoothing capacitor detected by the voltage detecting section is less than a set value.