JP2006034000A - Rush current prevention circuit for air conditioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit that effectively suppresses a rush current passing when three-phase power is applied and prevents breakdown of a rectifying device and a smoothing capacitor. <P>SOLUTION: A relay 3 for charging a smoothing capacitor 6 is provided at least in two phases in parallel with a three-phase electromagnetic switch 2, and a rush current prevention resistor 4 is provided in series with the relay 3 for charging. When a three-phase alternating-current power source 1 is turned on, the smoothing capacitor 6 is charged through the relay 3 for charging and the rush current prevention resistor 4. After a predetermined time has passed, the smoothing capacitor 6 is charged through the three-phase electromagnetic switch. Thus, the elements in a rectifying circuit 5 or the smoothing capacitor 6 is prevented from being broken down by a rush current passing when the three-phase alternating-current power source is turned on. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an inrush current prevention circuit for an air conditioner.

  Hereinafter, a conventional inrush current preventing circuit of an air conditioner will be described. In general, an inrush current prevention circuit of an air conditioner is used to prevent an inrush current when power is turned on and to prevent a semiconductor element or the like from being destroyed by the inrush current. As an example, there is one configured as shown in FIG. 5 (see, for example, Patent Document 1).

  In FIG. 5, the rectification which consists of a diode bridge etc. via the relay board | substrate 105 provided with the three-phase alternating current power supply 100, the relay 101 connected for every phase, the relay 102, the relay 103, and the resistance 104 for inrush current prevention. Connected to the circuit 106, the direct current rectified by the rectifier circuit 106 is smoothed by the smoothing capacitor 107 and supplied to the inverter device 108.

  The inverter device 108 is configured to arbitrarily control the rotational speed of the motor by supplying a three-phase alternating current to a motor load 109 such as a compressor and controlling the frequency. Further, the contacts of the relays 101 to 103 are turned on / off according to instructions from the control device 110.

  Here, of the relays connected for each phase, when the relay 102 or the relay 103 is turned on according to an instruction from the control device 110, the inrush current preventing resistor 104 and the rectifier circuit connected in parallel to the relay 101 Since charging of the smoothing capacitor 107 is started via 106, inrush current can be prevented.

Next, when the relay 101 and the relay 102 or the relay 103 are turned on, the smoothing capacitor 107 is charged via the relay 101 and the rectifier circuit 106, and three-phase alternating current is supplied to the inverter device 108. Thereby, the inverter device 108 is driven, the motor load 109 is arbitrarily controlled, and the operation is performed.
JP-A-8-19265

  However, in the conventional example described in Patent Document 1, since the relays 101 to 103 connected to each phase are arranged on the printed circuit board, the size of the relays that can be used is limited, and the allowable current value Therefore, there is a problem that it is not suitable for an inrush current prevention circuit of a high-capacity air conditioner that requires a large current.

  Moreover, many relays are arrange | positioned and it had the subject that the control structure for operating each relay suitably was complicated.

  In addition, when each relay is installed on a printed circuit board (not shown), it is necessary to secure an insulation distance, which increases the area of the printed circuit board and increases the installation space for the printed circuit board. It was.

In order to solve the above-described conventional problems, an inrush current prevention circuit for an air conditioner according to the present invention includes a three-phase electromagnetic switch provided on the input side of a rectifying / smoothing circuit and a parallel connection with the three-phase electromagnetic switch. And
An inrush current prevention resistor for suppressing an inrush current flowing when the three-phase power is turned on, and a charging relay connected in series with the inrush current prevention resistor to form a circuit for precharging a smoothing capacitor, A magnetic contactor type for main circuit switching with a large allowable current is used for the switch.

  INDUSTRIAL APPLICABILITY The present invention can effectively prevent an inrush current that flows when a three-phase power source is turned on with simple control in an air conditioner, and has an effect of preventing a rectifying element and a smoothing capacitor from being destroyed.

  In the first invention, a large three-phase electromagnetic switch having a large allowable current is provided on the input side of the rectifying / smoothing circuit, and a charging relay is connected in parallel to at least two phases, and at least one phase of the charging relay is provided. By connecting the inrush current prevention resistor in series, the inrush current when the three-phase power supply is turned on can be effectively prevented.

  In the second invention, in particular, the large three-phase electromagnetic switch according to the first invention can effectively prevent an inrush current when the three-phase power is turned on by using a single-phase type electromagnetic switch. Since the electromagnetic switch can be downsized, the installation space can be reduced.

  The third invention uses the large three-phase electromagnetic switch of the first invention in particular, the type of large three-phase electromagnetic switch having an A contact switch and a B contact switch, and the A contact switch has a three-phase main switch. By connecting a circuit and connecting an inrush current prevention resistor in series to at least one phase to the B contact switch to form an inrush current prevention circuit, it is possible to effectively prevent an inrush current flowing when a three-phase power supply is turned on. Since a charging relay for a smoothing capacitor is not required, it is possible to reduce component costs and installation man-hours.

  4th invention can simplify control of a large-sized three-phase electromagnetic switch and a charging relay by using the control means which collectively turns on / off the contacts of a large-sized three-phase electromagnetic switch. .

(Embodiment 1)
FIG. 1 is an electric circuit diagram showing a configuration of an inrush current preventing circuit of an air conditioner according to Embodiment 1 of the present invention. Hereinafter, the configuration of the inrush current prevention circuit will be described with reference to FIG.

  In a large-capacity air conditioner using the three-phase AC power source 1 as a main power source, a large-sized air conditioner connected to a three-phase three-wire between the rectifier circuit 5 that rectifies the three-phase AC power source 1 with a rectifier such as a diode bridge An electromagnetic contactor type three-phase electromagnetic switch 2 and a large three-phase electromagnetic switch 2 connected in parallel to at least two phases, connected in series with an inrush current preventing resistor 4 and precharged for a smoothing capacitor 6 A charging relay 3 forming a circuit is connected.

  The rectifier circuit 5 and the smoothing capacitor 6 rectify and smooth the three-phase alternating current to direct current, and are supplied to a three-phase inverter device 7 that supplies a three-phase output to the motor 8. The motor 8 is operated at an arbitrary frequency.

  The large three-phase electromagnetic switch 2 and the charging relay 3 are connected to a control means 9 such as a microcomputer for controlling the opening and closing of the contacts. Control is performed to keep the contacts of the switch 2 and the charging relay 3 on.

  The circuit operation of the inrush current prevention circuit when the three-phase power supply is turned on will be described below.

  In order to prevent an inrush current generated when the three-phase power is turned on, it is necessary to charge the smoothing capacitor 6 in advance. Therefore, when the three-phase power supply enters, first, a signal for turning on the charging relay 3 is transmitted from the control means 9 to the charging relay 3. As a result, the alternating current for two phases of the three-phase three-wire is rectified by the rectifier circuit 5 via the contact of the charging relay 3 and the inrush current preventing resistor 4 and charged to the smoothing capacitor 6.

  Since the current passes through the inrush current preventing resistor 4 and is charged into the smoothing capacitor 6, it is possible to effectively prevent the inrush current at the start of charging.

  Next, a signal for turning on the contact of the large three-phase electromagnetic switch 2 from the control means 9 and then turning off the contact of the charging relay 3 is sent to the large three-phase electromagnetic switch 2 and the charging relay 3. Sent.

  As a result, the three-phase alternating current from the three-phase alternating current power source 1 passes through the large three-phase electromagnetic switch 2 and is rectified by the rectifier circuit 5 to become direct current, smoothed by the smoothing capacitor 6 and supplied to the inverter device 7. The motor 8 is operated at a frequency of

  According to the above embodiment, in a high-capacity air conditioner, an inrush current that flows when a three-phase power source is turned on can be effectively prevented, and a rectifier element and a smoothing capacitor can be prevented from being destroyed.

(Embodiment 2)
FIG. 2 is an electric circuit diagram showing a configuration of an inrush current preventing circuit for an air conditioner according to Embodiment 2 of the present invention. In FIG. 1, the large three-phase electromagnetic switch is changed to a single-phase type electromagnetic switch. It is what. Hereinafter, a configuration of an inrush current prevention circuit using a single-phase type electromagnetic switch will be described.

  In a high-capacity air conditioner using a three-phase AC power source 1 as a main power source, the three-phase AC power source 1 is connected to at least two phases of three-phase three-wires with a rectifier circuit 5 that rectifies with a rectifier such as a diode bridge. A circuit for precharging the smoothing capacitor 6 connected in parallel with at least one phase of the single-phase type electromagnetic switch 10 and the single-phase type electromagnetic switch 10 connected in series with the inrush prevention resistor 4. A charging relay 11 for one circuit to be formed is connected. Further, one phase of the three-phase three-wire is directly connected to the rectifier circuit 5.

  The rectifier circuit 5 and the smoothing capacitor 6 rectify and smooth the three-phase alternating current to direct current, and are supplied to the three-phase inverter device 7 that supplies the three-phase output to the motor 8. The motor 8 is operated at an arbitrary frequency. .

  A control means 9 such as a microcomputer for controlling the opening and closing of the contacts is connected to the single-phase type electromagnetic switch 10 and the charging relay 11 for one circuit. Control is performed so as to keep the contacts of the phase type electromagnetic switch 10 and the charging relay 11 for one circuit on.

  According to the above embodiment, since the three-phase electromagnetic switch can be changed to a single-phase type electromagnetic switch, the installation space is reduced, the parts cost is reduced, and the inrush current that flows when the three-phase power supply is turned on Can be effectively prevented, and the rectifying element and the smoothing capacitor can be prevented from being destroyed.

(Embodiment 3)
FIG. 3 is an electric circuit diagram showing a configuration of an inrush current preventing circuit for an air conditioner according to Embodiment 3 of the present invention. In FIG. 1, a large three-phase electromagnetic switch is replaced with a three-phase circuit having A and B contacts. It has been changed to an electromagnetic switch. Hereinafter, the configuration of an inrush current prevention circuit using a three-phase electromagnetic switch having an A contact and a B contact will be described.

  In a high-capacity air conditioner using a three-phase AC power source 1 as a main power source, a contact and b contact are connected to a three-phase three-wire between the three-phase AC power source 1 and a rectifier circuit 5 that rectifies the three-phase AC power source 1 with a rectifier such as a diode bridge. Are connected to the R-phase a-contact 12a, the S-phase a-contact 12c, and the T-phase a-contact 12d. In addition, for example, the R-phase b-contact 12b and the T-phase of the three-phase electromagnetic switch 12 that forms a circuit for precharging the smoothing capacitor 6 and has at least two of the three-phase three-wires have a-contact and b-contact. B contact 12e, and at least one of them is connected in series with inrush prevention resistor 4.

  The rectifier circuit 5 and the smoothing capacitor 6 rectify and smooth the three-phase alternating current to direct current, and are supplied to the three-phase inverter device 7 that supplies the three-phase output to the motor 8. The motor 8 is operated at an arbitrary frequency. .

  A control means 9 such as a microcomputer for controlling the opening and closing of the a and b contacts is connected to the three-phase electromagnetic switch 12 having the a and b contacts. Control is performed so as to maintain the ON state of the a contact and the b contact of the three-phase electromagnetic switch 12 having the contact and the b contact.

  According to the above embodiment, the inrush current that flows when the three-phase power is turned on without changing the charging relay by changing the three-phase electromagnetic switch to the three-phase electromagnetic switch 12 having the a-contact and the b-contact. Can be effectively prevented, and the rectifying element and the smoothing capacitor can be prevented from being destroyed. In addition, the installation space can be reduced, and the parts cost and the number of parts can be reduced.

(Embodiment 4)
FIG. 4 shows a charging relay when the three-phase power is turned on and a means for controlling the state in which the three-phase electromagnetic switch is kept on in the inrush current prevention circuit for the air conditioner according to Embodiment 4 of the present invention. It is a flowchart. In addition, S1-S8 in a figure shows each step of a flowchart.

  First, it is determined whether there is an instruction to start operating the air conditioner in S1, and if there is an instruction, the contact of the charging relay is turned on in S2. Since an inrush current flows here, the smoothing capacitor is charged via the inrush current prevention circuit. After the elapse of the first predetermined time t, the contact of the large three-phase electromagnetic switch of the main circuit is turned on and the contact of the charging relay is turned off in S4. Thereby, a direct current required for the inverter device is supplied, and the inverter device can be driven to operate the motor.

  Next, it is determined whether there is an instruction to stop the operation of the air conditioner. If there is an instruction, the contact of the large three-phase electromagnetic switch is turned off in S8 after the second predetermined time t has elapsed. Then return to S1 again and repeat the following.

  In other words, compared to the conventional on / off timing control for each of the three relays, it is simpler control that collectively turns on / off the contacts of the charging relay and large three-phase electromagnetic switch. Therefore, the inrush current can be effectively prevented, and the destruction of the rectifying element and the smoothing capacitor can be prevented.

The inrush current prevention circuit according to the present invention has an effect of effectively preventing an inrush current that flows when a three-phase power source is turned on in a high-capacity air conditioner, and is useful for preventing destruction of a rectifying element and a smoothing capacitor. is there.

FIG. 1 is an electric circuit diagram of an inrush current prevention circuit for an air conditioner according to Embodiment 1 of the present invention. Electric circuit diagram of inrush current prevention circuit of air conditioner in Embodiment 2 of the present invention Electric circuit diagram of inrush current prevention circuit of air conditioner in Embodiment 3 of the present invention The flowchart which showed the means which controls the state holding ON of the three-phase electromagnetic switch of this invention Electric circuit diagram of inrush current prevention circuit of conventional air conditioner

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Three-phase alternating current power supply 2 Three-phase electromagnetic switch 3 Charging relay 4 Inrush current prevention resistance 5 Rectifier circuit 6 Smoothing capacitor 7 Inverter device 8 Motor 9 Control means 10 Single-phase type electromagnetic switch 11 Relay for charge for 1 circuit 12 Three-phase electromagnetic switch having a contact and b contact 12a R contact a contact 12b R contact b contact 12c S contact a contact 12d T contact a contact 12e T contact b contact 100 Three-phase AC power supply 101 Relay 102 Relay 103 Relay 104 Inrush Current Prevention Resistance 105 Relay Board 106 Rectifier Circuit 107 Smoothing Capacitor 108 Inverter Device 109 Motor Load 110 Control Device

Claims (4)

In an air conditioner that converts a three-phase AC power source into a direct current using a rectifying / smoothing circuit, supplies it to a three-phase inverter device, converts it into a three-phase alternating current using the three-phase inverter device, and drives a motor or the like at an arbitrary frequency. A three-phase electromagnetic switch provided on the input side of the rectifying / smoothing circuit; and an inrush current preventing resistor connected in parallel with the three-phase electromagnetic switch for suppressing an inrush current flowing when a three-phase power supply is turned on; A charging relay connected in series with the inrush current prevention resistor to form a circuit for charging a smoothing capacitor in advance, the three-phase electromagnetic switch of the electromagnetic contactor type for main circuit switching with a large allowable current An inrush current prevention circuit for an air conditioner characterized by using a thing. The inrush current preventing circuit for an air conditioner according to claim 1, wherein a single-phase electromagnetic switch is used instead of the three-phase electromagnetic switch. By using an electromagnetic switch having a-contact (Normal Open) and b-contact (Normal Close) for the three-phase electromagnetic switch, an inrush current prevention circuit is constructed without using a charging relay for charging a smoothing capacitor. The inrush current preventing circuit for an air conditioner according to claim 1. At the start of operation of the air conditioner, after turning on the charging relay, the three-phase electromagnetic switch is turned on after the first predetermined time and the charging relay is turned off. When the operation is stopped, the three-phase is turned on after the second predetermined time. 2. The inrush current preventing circuit for an air conditioner according to claim 1, further comprising a control means for turning off the electromagnetic switch.

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