Low volume variable rpm submersible well pump

• US 4,678,404 A
• Filed: 01/24/1986
• Issued: 07/07/1987
• Est. Priority Date: 10/28/1983
• Status: Expired due to Fees

• Current Assignee: Baker Hughes Incorporated (Baker Hughes Company)
• Original Assignee: Hughes Tool Company (Baker Hughes Company)
• Inventors: Vandevier, Joseph E., Lorett, Jerzy A.
• Primary Examiner(s): Croyle, Carlton R.
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/822,358
• Time in Patent Office: 529 Days
• Field of Search: 417/42-45, 417/53, 417/410, 417/424, 415/501, 166/53, 166/65 R, 166/68
• US Class Current: 417/45
• CPC Class Codes: F04D 13/10 adapted for use in mining bore holes
• CPC Class Codes: F04D 15/0066 by changing the speed, e.g. of the driving engine
• CPC Class Codes: Y10S 415/901 Drilled well-type pump

Abstract

A low volume submersible pump assembly has features to stabilize the operation. The pump assembly includes a centrifugal pump driven by a submerged electrical motor. The centrifugal pump has an impeller configuration that is designed for high specific head, but potentially unstable operation. At the design speed, the pump potentially could deliver an indeterminate flow rate for a given head. Also, at the design speed, the design flow rate will yield a design head that is very close to the maximum head at zero flow. The pump has the characteristic of requiring a significant increase in torque to produce higher flow rates. To stabilize the potentially unstable pump, a variable speed drive varies the speed of the motor to maintain constant torque. Maintaining a constant torque allows a considerable variance in head with only a small variance in flow rate resulting.

Claims

1. A submersible pump assembly comprising in combination:

a centrifugal pump having impeller means for producing at least two flow rates for a selected head when operated at constant speed, making the pump potentially unstable, and for requiring increasing torque to produce increasing flow rates;

an electric motor connected directly to the pump for driving the pump;

sensing means for sensing the torque output of the motor; and

variable speed drive means for varying the speed of the motor in response to the torque sensed by the sensing means to maintain a constant torque output, the constant torque applied to the pump preventing the pump from delivering more than one flow rate for a given head to stabilize the operation.

2. A submersible pump assembly, comprising in combination:

a centrifugal pump having impeller means for producing a constant design speed head/flow curve with a design flow rate and a design head selected such that the maximum head at zero flow rate and the design speed is no more than about 20% greater than the design head at the design speed, rendering the pump potentially unstable at the design speed, and for requiring an increase in torgue as the flow increases;

an electric motor connected to the pump for driving the pump;

sensing means for sensing the torque output of the motor; and

variable speed drive means for varying the speed of the motor in response to the torque sensed by the sensing means to maintain the torque constant at a selected torque for stabilizing the pump operation.

3. A submersible pump assembly comprising in combination:

a centrifugal pump having impeller means with an exit angle in the range from 45 to 60 degrees for producing a constant design speed head/flow curve with a design flow rate and a design head selected such that the maximum head at the design speed and zero flow rate is no more than about 20% greater than the design head at the design speed, rendering the pump potentially unstable at the design speed due to unexpected increases in head, and for producing a constant variable speed torque line that when plotted on a constant speed head/flow graph with a head/flow curve, has a greater negative slope than the head/flow curve in the range from zero flow to design flow;

an electric motor connected directly to the pump for driving the pump;

sensing means for sensing the torque output of the motor; and

variable speed drive means for varying the speed of the motor in response to the torque sensed by the sensing means to maintain the torque constant at a selected level for stabilizing the pump operation.

4. A method of pumping a well with a submersible pump assembly comprising in combination:

providing a centrifugal pump with potentially unstable impellers of a type that will produce at least two flow rates for a selected head;

connecting an AC electric motor directly to the pump for driving the pump;

locating the pump and motor in the well and providing electrical cables that extend to the surface;

connecting the cables to an electrical variable speed drive located at the surface, which is of a type that will vary the speed of the motor by varying the frequency of the electrical power supplied;

sensing the torque output of the motor; and

varying the variable speed drive and thus the speed of the motor to maintain constant torque output of the motor, the constant torque output applied to the pump, preventing the pump from delivering more than one flow rate for a given head, to stabilize the operation.

5. A method of pumping a well with a submersible pump assembly comprising in combination:

providing a centrifugal pump with potentially unstable impellers, each impeller being of a type having vanes with an exit angle in the range from 45 degrees to 60 degrees so as to produce at least two flow rates for a selected head;

connecting an AC electric motor directly to the pump for driving the pump;

locating the pump and motor in the well and providing electrical cables that extend to the surface;

connecting the cables to an electrical variable speed drive located at the surface, which is of a type that will vary the speed of the motor by varying the frequency of the electrical power supplied;

sensing the current supplied to the motor; and

varying the variable speed drive and thus the speed of the motor to maintain constant current, which produces a constant torque output of the motor, the constant torque output applied to the pump preventing the pump from delivering more than one flow rate for a given head, to stabilize the operation.