Method for the operation of a centrifugal pump

• US 20020176783A1
• Filed: 03/13/2002
• Published: 11/28/2002
• Est. Priority Date: 04/02/2001
• Status: Active Grant

• Current Assignee: Danfoss Drives A/S (Danfoss A/S)
• Original Assignee: Danfoss Drives A/S (Danfoss A/S)
• Inventors: Moeller, Eik Sefeldt
• Granted Patent: US 6,715,996 B2
• Time in Patent Office: Days
• US Class Current: 417/44.11
• CPC Class Codes: F04D 15/0066 by changing the speed, e.g. of the driving engine
• CPC Class Codes: F04D 15/0227 Lack of liquid level being detected using a flow transducer
• CPC Class Codes: F04D 15/0236 Lack of liquid level being detected by analysing the parameters of the electric drive, e.g. current or power consumption

Abstract

A method for the operation of a centrifugal pump (2) driven by an electric motor (5) with variable frequency, wherein too small a flow through the pump (2) is ascertained by monitoring electrical quantities, and a pump arrangement (1) having a centrifugal pump (2), an electric motor (5) which drives the centrifugal pump (2), a controlled frequency converter (6) which feeds the electric motor (5), a sensor device (12, 13) and an evaluating device (15-19) are described.

It is desired to detect, by simple means, when no through-flow is present.

For that purpose, the electrical power is ascertained and compared to a control quantity formed as a function of the frequency of the motor (5). The sensor device ascertains values for determination of the electrical power, and the evaluating device has a dynamic limit value former (18), which forms a control quantity as a function of the frequency of the motor (5).

Claims

1. Method for the operation of a centrifugal pump driven by an electric motor with variable frequency, wherein too small a flow through the pump is ascertained by monitoring electrical quantities, characterized in that the electrical power is ascertained and compared to a control quantity formed as a function of the frequency of the motor.

2. Method according to claim 1, characterized in that the control quantity is ascertained with the aid of a reference power which applies at a predetermined reference frequency.

3. Method according to claim 1 or 2, characterized in that the control quantity includes a product, one of the factors of which can be specified by a user.

4. Method according to claim 3, characterized in that the factor is selected to be greater than unity.

5. Method according to any one of claims 1 to 4, characterized in that at least two measurements of the power of the motor are made at different frequencies and without flow through the centrifugal pump, and a basis for the control quantity is ascertained therefrom.

6. Method according to claim 5, characterized in that the basis is ascertained in accordance with the following formula:

7. Method according to claim 6, characterized in that the control quantity is determined in accordance with the following relationship:

8. Pump arrangement having a centrifugal pump, an electric motor which drives the centrifugal pump, a controlled frequency converter which feeds the electric motor, a sensor device and an evaluating device, characterized in that the sensor device ascertains values for determination of the electrical power, and the evaluating device has a dynamic limit value former, which forms a control quantity as a function of the frequency of the motor.