Method and apparatus for current measurement for electronically-controlled pump

• US 6,801,031 B1
• Filed: 09/01/1999
• Issued: 10/05/2004
• Est. Priority Date: 09/04/1998
• Status: Expired due to Fees

• Current Assignee: Pierburg GmbH (Rheinmetall AG)
• Original Assignee: WILO GmbH
• Inventors: Stephan, Waldemar
• Primary Examiner(s): Nguyen, Vinh P.
• Application Number:
  US09/388,813
• Time in Patent Office: 1,861 Days
• Field of Search: 324/73.1, 324/158.1, 324/126-127, 324/142, 324/545, 324/772, 702/60, 322/99, 318/68, 318/490, 318/68.C, 361/86, 361/93, 361/31, 361/93.7, 700/170, 700/90
• US Class Current: 324/126
• CPC Class Codes: G01R 1/203 Resistors used for electric measuring, e.g. decade resistors standards, resistors for comparators, series resistors, shunts resistors in general H01C; microwave or radiowave terminations H01P1/26; coupling devices H01R
• CPC Class Codes: G01R 19/0092 measuring current only all subgroups of G01R19/00 take precedence
• CPC Class Codes: G01R 31/343 in operation

Abstract

The current draw of a pump driven by an electric motor, especially a centrifugal pump such as a heating-system circulating pump, is measured by detecting the voltage drop across a conductor segment connecting the power side and hence the power line to the motor control circuit. This eliminates the need for a separate measurement resistor.

Claims

1. A method of determining a current draw of a pump driven by an electric motor, and a motor control circuit being connected to said motor by a power line said method comprising the steps of:

(a) measuring a voltage drop across at least a portion of a conductor having a definite resistance and connecting said power line with said motor-control circuit; and

(b) calculating said current draw from said voltage drop.

2. The method defined in claim 1 wherein said portion of said conductor having said resistance is a piece of current supply line connecting the power line with said motor-control circuit.

3. The method defined in claim 1 wherein the voltage drop is measured and the current draw is calculated from said voltage drop by a computing unit forming part of said motor-control circuit.

4. The method defined in claim 1 wherein a current measured in said portion of said conductor is converted into a current draw of said pump.

5. The method defined in claim 1 wherein in calculating said current draw from said voltage drop, a computer unit forming part of said motor control circuit compensates for a temperature of said portion of said conductor.

6. An electronically controlled pump assembly comprising:

an electric motor having a power line connected thereto for energizing said electric motor;

a motor control circuit connected to said motor and said power line for electronically controlling said pump assembly;

a pump driven by said motor; and

means for measuring a voltage drop across at least a portion of a conductor in the form of a wire segment having a definite resistance and connecting said power line with said motor control circuit and calculating said current draw from said voltage drop.

7. The assembly defined in claim 6 wherein said portion of said conductor is a piece of resistance wire with a known specific resistance and a defined length.

8. The assembly defined in claim 6 wherein said portion of said conductor is a bridge between a plug contact to which said power line is connected and a printed circuit board carrying said motor control circuit, said bridge having a defined resistance.

9. The assembly defined in claim 6 wherein said resistance is between 1 and 5 mΩ

.

10. The assembly defined in claim 6, further comprising a processor forming part of said motor control circuit and constituting the means for measuring and calculating.

11. The assembly defined in claim 10 wherein said processor is provided to effect a regulatory action in response to the temperature of said portion of said conductor.