JPS61167392A - Motor drive device of air conditioner - Google Patents

Abstract

PURPOSE:To improve the power factor of a power source by rectifying a single- phase AC and driving a 3-phase motor by 3-phase output inverter, thereby enabling to use a transistor of a rated low current to reduce power loss. CONSTITUTION:The output of a single-phase 100V power source PS is applied to a bridge circuit of dioded D and capacitors C of a rectifier REC to produce a double voltage rectified output between both terminals of a capacitor C0, applied to an inverter INV of transistors Q1-Q6, and converted to 3-phase 200V. The 3-phase output frequency is set variable by controlling the bases of the transistors Q1-Q6 of the inverter INV.

Description

[Detailed description of the invention] The present invention relates to a motor drive device for an air conditioner.

In recent years, transistor inverters have been improved, and inverters are now being applied to home air conditioners, and variable capacity air conditioners have been developed. Figure 1 is an example of this, and single-phase power supply A single-phase induction motor CM is driven by a variable frequency inverter CC that obtains a single-phase output from the PS.

However, in this case, starting improvement elements unique to single-phase induction motors, that is, a starting capacitor C8 and a starter S are required, and the inverter main circuit transistor of the single frequency variable device CC is a large current rated transistor, resulting in high cost and transistor loss. big. In particular, the cost of power transistors increases significantly when the rated current exceeds 15A, and IHP class air conditioners, which are the mainstay of home air conditioners, require transistors rated at 20 to 30A when using a single-phase compressor. Therefore, commercialization is hampered by cost.

The present invention has been made in view of the above-mentioned points, and uses a three-phase output inverter to drive a three-phase motor, and provides direct current obtained by rectifying single-phase alternating current to the three-phase output inverter. , a motor drive device for an air conditioner that drives a three-phase motor with a single-phase current.

An embodiment of the present invention will be described below with reference to FIGS. 2 and 3.

FIG. 2 shows the basic configuration of an embodiment of the present invention.
The single-phase power supply PS is supplied to the fan motor FM and the three-phase output frequency converter CC via the power switch SW, and the output of the frequency converter CC is supplied to the three-phase compressor motor CM.

This three-phase output frequency converter CC and three-phase compressor motor C
The reason for the combination with M is as follows.

In general, the relationship between the motor's power consumption (P) and electric current and FFE is as follows: If the power factor is ψ, then for a single-phase motor, P = E.
It is expressed as I ctsψ. On the other hand, among household air conditioners, those that are used for both cooling and heating consume about 1.5 KW and have a power factor of about 0.9. Calculating the current from this, I = P/FJ - ψ = 1500/100
) or more is required.

On the other hand, with a three-phase motor, the motor current is between 5 and 5, and the system can be constructed using inexpensive transistors with a rated current of 15 or less (aluminum or less). Although the number has increased from 4 in 3-phase to 6 in 3-phase, the loss per unit is 5.
/17, resulting in a total of 6/4 x 5/17/0
．． 4, which improves conversion efficiency. Additionally, the starting capacitor and starter that are unique to single-phase induction motors are no longer required.

Figure 3 shows the main circuit configuration of the three-phase output frequency converter for the second factor. A voltage doubler rectified output is applied to a bridge circuit and taken out across a capacitor Cn, and is applied to an inverter INVK consisting of transistors Q1 to Q6 for three-phase 200 (V) conversion. And the transistor Q of the inverter INV, ~
The three-phase output frequency is made variable by performing base control of Q6.

In the above embodiment, a transistor inverter is used as an example, but it goes without saying that a thyristor inverter may also be used.

As described above, the present invention rectifies single-phase alternating current and supplies it to a three-phase output inverter to drive a three-phase motor, which eliminates all problems with conventional single-phase motors and provides various advantages. It will be done. In other words, costs can be reduced because transistors with low current ratings can be used, three-phase motors have a large starting torque and do not require any starting elements, the power loss of transistors is small, the conversion efficiency of the device is high, and voltage doubling is possible. Connecting an inductance to the rectifier circuit can improve the power factor of the power supply.

[Brief explanation of the drawing]

Fig. 1 is a main circuit configuration diagram of a conventional single-phase air conditioner motor drive device, Fig. 2 is a diagram showing an embodiment of the present invention, and Fig. 3 is used in the embodiment of Fig. 2. FIG. 3 is a circuit diagram of a three-phase output frequency variable device.

Claims (1)

[Claims] A single-phase power source, a rectifier circuit that rectifies the alternating current supplied from the single-phase power source and outputs a direct current output, and a
An air conditioner motor drive device that includes an inverter circuit that converts phase alternating current to a three-phase compressor motor that receives power from the inverter.