JPH04246285A - Starter for compressor - Google Patents

Abstract

PURPOSE:To start a compressor without damaging the compressor even if the inside of the compressor is filled with liquid. CONSTITUTION:On the start of a compressor, if the frequency difference between the inverter frequency and the revolution frequency of the compressor exceeds the first set value, the increase of the inverter frequency is suspended up to the time when the frequency difference becomes less than the second set value which is smaller than the first set value.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an inverter-driven compressor,
In particular, the present invention relates to a starting device suitable for a compressor that compresses refrigerant, such as an air conditioner.

0002

[Prior art and its problems] In this type of compressor,
If the compressor is stopped for a long time, such as when the temperature is low, the refrigerant liquefies and accumulates inside the compressor. In this state, when the operation switch is turned on to start the compressor, the inverter frequency rises at a constant speed (for example, 2 Hz/sec) to the command frequency D in proportion to the passage of time, as shown in Figure 4, and the compression Since the machine compresses the liquid refrigerant drawn into the compression chamber, its rotational speed increases at a speed much slower than the inverter frequency. As shown in Figure 5, as the inverter frequency increases, the voltage and motor torque increase, but when the motor torque increases, the cylinder pressure in the compression chamber increases abnormally, potentially damaging the compressor. .

0003

[Means for Solving the Problems] The present invention was invented to solve the above problems, and its gist is to provide a compressor driven by a motor to which current is supplied via an inverter. means for calculating a frequency difference between the frequency of the inverter and the rotational frequency of the compressor; and a means for calculating the frequency difference between the frequency of the inverter and the rotation frequency of the compressor; A compressor starting device characterized by comprising means for stopping an increase in inverter frequency until a frequency difference becomes equal to or less than a second set value.

0004

[Operation] Since the present invention has the above configuration, when the compressor is started, the frequency difference between the inverter frequency and the compressor rotation frequency is calculated, and the calculated frequency difference is the first
When the set value is exceeded, the increase in the inverter frequency is thereafter stopped until the frequency difference becomes equal to or less than the second set value.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to FIGS. 1 to 3. As shown in FIG. 1, current from a power source 1 is supplied to a motor 3 via an inverter 2,
A compressor 4 is driven by this motor 3. Compressor 4
When the operation switch is turned on to start the inverter 2, the inverter frequency of the inverter 2 starts increasing. The rotational speed of the compressor 4 is detected by the sensor 5, converted into a rotational frequency by the conversion means 6, and input to the calculation means 7. At the same time, the inverter frequency of the inverter 2 is detected by the sensor 8 and inputted to the calculation means 7, where the difference between the two is calculated.
A frequency difference is calculated. The calculated frequency difference is input to the comparison means 9, where it is compared with the first set value A input from the A value setting means 10. When the frequency difference is larger than the first set value A (for example, 20 Hz), the comparison means 9 outputs an output to the acceleration control means 11. The acceleration control means 11 determines to stop acceleration of the inverter frequency when the inverter frequency input from the inverter frequency sensor 8 is equal to or higher than a certain frequency B between 20 and 40 Hz input from the B value setting means 12. However, this output is outputted to the inverter 2 via the output means 13, and the increase in the inverter frequency is stopped. However, when the inverter frequency is lower than frequency B, the acceleration of the inverter frequency is not stopped, thereby preventing poor lubrication in the low speed rotation range of the compressor. Even while the increase in the inverter frequency is stopped, the rotation speed of the compressor increases, and the frequency difference is inputted from the C value setting means 13.
When the inverter frequency becomes less than a set value C (for example, 10Hz) (where C<A), the acceleration control means 11 determines the acceleration of the inverter frequency. When the inverter frequency increases to the command value D input from the D value setting means 14 by repeating the above steps, the increase in the inverter frequency is stopped, and the inverter frequency is maintained at the command value D thereafter.

Note that the inverter frequency can be easily detected by connecting the output terminal of the inverter 2 to the sensor 8. Further, the rotation speed of the compressor 4 can be detected by measuring pressure pulsations using a pressure sensor, measuring vibrations using an acceleration sensor, or the like.

[0007]

[Effect of the invention] In the present invention, when starting the compressor, the frequency difference between the inverter frequency and the compressor rotation frequency is calculated, and if the calculated frequency difference exceeds the first set value, the The increase in the inverter frequency is stopped until the frequency difference becomes equal to or less than the second set value. In this way, by stopping the increase in the inverter frequency, the increase in motor torque is also stopped, so that an abnormal increase in the cylinder pressure of the compressor can be suppressed and damage to the compressor can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a control block diagram showing one embodiment of the present invention.

FIG. 2 is a diagram showing temporal changes in inverter frequency and compressor rotation speed in the above embodiment.

FIG. 3 is a control flowchart of the above embodiment.

FIG. 4 is a diagram showing temporal changes in inverter frequency and compressor rotation speed in a conventional device.

FIG. 5 is a diagram showing the relationship between inverter frequency, voltage, and motor torque in a conventional device.

[Explanation of symbols]

2 Inverter 3 Motor 4 Compressor 7 Frequency difference calculation means 11 Frequency rise stopping means

Claims (1)

[Claims] 1. A compressor driven by a motor to which current is supplied via an inverter, comprising: means for calculating a frequency difference between the frequency of the inverter and the rotational frequency of the compressor; and means for stopping the increase in the inverter frequency from when the frequency difference calculated by the calculation means exceeds a first set value until the frequency difference becomes equal to or less than a second set value. Compressor starting device.