FLUID MACHINERY

• US 20020018721A1
• Filed: 10/25/1999
• Published: 02/14/2002
• Est. Priority Date: 04/25/1997
• Status: Active Grant

• Current Assignee: Ebara Corporation
• Original Assignee: Ebara Corporation
• Inventors: KOBAYASHI, MAKOTO, YAMAMOTO, MASAKAZU, MIYAZAKI, YOSHIAKI, MIYAKE, YOSHIO, IIJIMA, KATSUJI, UWAI, KEITA, YAGI, KAORU
• Granted Patent: US 6,350,105 B1
• Time in Patent Office: Days
• US Class Current: 417/44.1
• CPC Class Codes: F04D 15/0066 by changing the speed, e.g. of the driving engine

Abstract

The present invention relates to a fluid machinery for generating a pressure by rotating an impeller with a motor. The fluid machinery has a frequency converter (F) for supplying electric power to the motor, a detector for detecting a frequency and a current value, and a program for specifying in advance the relationship between the frequency and the current value. A frequency and a current value in an actual operation are compared with the specified program, and the frequency generated by the frequency converter (F) is varied so that an operating point of the fluid machinery approaches the specified program.

Claims

1. A fluid machinery for generating a pressure by rotating an impeller with a motor, comprising:

a frequency converter for supplying electric power to the motor;

a detector for detecting a frequency and a current value; and

a program for specifying in advance the relationship between the frequency and the current value;

wherein a frequency and a current value in an actual operation are compared with the specified program, and the frequency generated by said frequency converter is varied so that an operating point of the fluid machinery approaches the specified program.

2. A fluid machinery according to claim 1, wherein said fluid machinery is such a type that a shaft power increases as a flow rate increases at a constant rotational speed, and the flow rate of said fluid machinery is controlled so as to be substantially constant even when a generated pressure varies.

3. A fluid machinery according to claim 1, wherein said fluid machinery is such a type that a shaft power decreases as a flow rate increases at a constant rotational speed, and a generated pressure is controlled so as to be substantially constant even when the flow rate varies.

4. A fluid machinery according to claim 1, wherein the frequency (Hz) and the current value (A) are related by a unique function and programmed.

5. A fluid machinery according to claim 4, wherein the relationship between said frequency (Hz) and said current value (A) is expressed by A=KHzⁿ (where K and n represent positive constants).

6. A fluid machinery according to claim 5, wherein said frequency converter has means for changing values of K and n.

7. A pump assembly comprising:

a centrifugal pump driven by a three-phase induction motor;

a frequency converter for supplying electric power to said three-phase induction motor;

a detector provided in said frequency converter for detecting a frequency and a current value; and

a program for specifying the relationship between the frequency and the current value which is stored by said frequency converter;

wherein a frequency and a current value in an actual operation are compared with the specified program, and the frequency generated by said frequency converter is varied so that an operating point of the pump approaches the specified program, and a flow rate is controlled so as to be substantially constant even when a pump head of said pump varies.

8. A pump assembly according to claim 7, wherein said pump assembly has a function for multiplying time outputted from said frequency converter by the value of the constant flow rate for thereby calculating the flow rate.

9. A pump assembly according to claim 8, wherein said frequency converter has an indicator for the flow rate.

10. A pump assembly according to claim 8, wherein by using a memory function of said frequency converter, said pump assembly can be automatically operated to perform a task of delivering a certain amount of water for an every certain period of time for a certain number of successive days, stop performing the task for a certain number of successive days, and perform the task for a certain number of successive days.