Pump system with liquid cooling operation

• US 5,563,490 A
• Filed: 09/20/1994
• Issued: 10/08/1996
• Est. Priority Date: 09/20/1993
• Status: Expired due to Fees

• Current Assignee: Ebara Corporation
• Original Assignee: Ebara Corporation
• Inventors: Kawaguchi, Kyoji, Yamamoto, Masakazu, Miyake, Yoshio, Uwai, Keita, Isemoto, Koji
• Primary Examiner(s): SALATA, ANTHONY J
• Application Number:
  US08/309,897
• Time in Patent Office: 749 Days
• Field of Search: 318/798-810, 363/40, 363/41, 363/55-58, 417/1, 417/18, 417/31, 417/32, 417/44
• US Class Current: 318/808
• CPC Class Codes: F04D 15/0066 by changing the speed, e.g. of the driving engine

Abstract

A pump control system has a pump unit composed of a turbo pump, a motor for operating the turbo pump, and a frequency/voltage converter for generating a frequency and a voltage to energize the motor. The rotational speed of the turbo pump is varied in order to equalize the current of the motor to a constant current irrespective of the head of the pump. The pump can be operated to take fully advantage of the current capacity of the motor.

Claims

1. A pump system comprising:

a pump unit composed of a turbo pump, a three-phase induction motor for operating said turbo pump, and a frequency/voltage converter for generating a frequency and a voltage to energize said three-phase induction motor, wherein an impeller of said turbo pump and a rotor of said motor are fixedly mounted on a main shaft which is supported by bearings, said motor also comprising a stator;

means for keeping a ratio of said voltage to said frequency constant and varying a rotational speed of said turbo pump in order to equalize a current of said three-phase induction motor to a constant current irrespective of a head of the pump; and

means for supplying a liquid pressurized by said impeller to at least one of spaces for thermal isolation between said stator and said bearings and between said stator and said rotor.

2. A pump system according to claim 1, wherein said means comprises a current detecting means for detecting said current of said motor, a current setting unit for setting said constant current, a comparator for comparing the detected current and the set constant current, and a frequency signal generator responsive to an output signal from said comparator for generating a frequency signal to vary said frequency in order to keep constant the current of said three-phase induction motor.

3. A pump system according to claim 2, further comprising means for setting an upper limit for said frequency signal to keep a rotational speed of said turbo pump below a predetermined speed.

4. A pump system according to claim 1, further comprising means for detecting a temperature of a stator winding of said three-phase induction motor, and control means for varying the constant current in order to keep the temperature of the stator winding below a predetermined value.

5. A pump system comprising:

a pump unit composed of a turbo pump, a motor for operating said turbo pump, and a frequency/voltage converter for generating a frequency and a voltage to energize said motor, wherein an impeller of said turbo pump and a rotor of said motor are fixedly mounted on a main shaft which is supported by bearings said motor also comprising a stator;

means for keeping a predetermined relationship of said voltage to said frequency and varying a rotational speed of said turbo pump in order to equalize a current of said motor to a constant current irrespective of a head of the pump; and

means for supplying a liquid pressurized by said impeller to at least one of spaces for thermal isolation between said stator and said bearings and between said stator and said rotor.

6. A pump control system according to claim 5, wherein said means comprises a current detecting means for detecting said current of said motor, a current setting unit for setting said constant current, a comparator for comparing the detected current and the set constant current, and a frequency signal generator responsive to an output signal from said comparator for generating a frequency signal to vary said frequency in order to keep constant the current of said motor.

7. A pump control system according to claim 6, further comprising means for setting an upper limit for said frequency signal to keep the rotational speed of said turbo pump below a predetermined speed.

8. A pump system according to claim 5, further comprising means for detecting a temperature of a stator winding of said motor, and control means for varying said constant current in order to keep said temperature of the stator winding below a predetermined value.

9. A pump system comprising:

a pump unit composed of a turbo pump, a motor for operating said turbo pump, and a frequency/voltage converter for generating a frequency and a voltage to energize said motor, wherein an impeller of said turbo pump and a rotor of said motor are fixedly mounted on a main shaft which is supported by bearings, said motor also comprising a stator;

means for equalizing a current of said three-phase induction motor to a constant current irrespective of a head of the pump; and

means for supplying a liquid pressurized by said impeller to a space for thermal isolation between said stator and a heat producing portion other than said stator.

10. A pump system according to claim 9, wherein said pump unit comprises a full-circumferential flow pump.

11. A pump system according to claim 9, wherein said pump unit comprises a canned motor pump.

12. A pump system according to claim 9, wherein said heat producing portion other than said stator is at least one of bearings and a motor rotor.

13. A pump system comprising:

a pump unit composed of a turbo pump, a motor for operating said turbo pump, and a frequency/voltage converter for generating a frequency and a voltage to energize said motor, wherein an impeller of said turbo pump and a rotor of said motor are fixedly mounted on a main shaft which is supported by bearings, said motor also comprising a stator;

means for equalizing a current of said three-phase induction motor to a constant current irrespective of a head of the pump; and

means for supplying a liquid to a space for thermal isolation between said stator and a heat producing portion other than said stator.

14. A pump system according to claim 13, wherein said pump unit comprises a full-circumferential flow pump.

15. A pump system according to claim 13, wherein said pump unit comprises a canned motor pump.

16. A pump system according to claim 13, wherein said heat producing portion other than said stator is at least one of bearings and a motor rotor.