Method for detecting a fault in an induction machine

• US 8,552,757 B2
• Filed: 04/08/2009
• Issued: 10/08/2013
• Est. Priority Date: 04/09/2008
• Status: Active Grant

• Current Assignee: Danfoss Drives A/S (Danfoss A/S)
• Original Assignee: Danfoss Drives A/S (Danfoss A/S)
• Inventors: Simon, Karl-Peter
• Primary Examiner(s): Assouad, Patrick
• Assistant Examiner(s): CURTIS, SEAN M
• Application Number:
  US12/937,138
• Publication Number:
  US 20110025371A1
• Time in Patent Office: 1,644 Days
• Field of Search: 324/765.01, 324/545, 324/546, 324/772, 318/490, 361/30, 702/58, 702/64
• US Class Current: 324/765.01
• CPC Class Codes: G01R 31/343 in operation
• CPC Class Codes: H02P 29/0241 the fault being an overvoltage

Abstract

The invention concerns a method for detecting a fault in a rotating field machine, in which current components are analysed in a flux-based, particularly rotor-flux-based, coordinate system a flux-forming current component being subjected to a frequency analysis in the flux-based, particularly rotor-flux-based, coordinate system. It is endeavored to provide a simple method for an early detection of faults. For this purpose, a current operating point is detected for at least one predetermined supply frequency (f_sp), said operating point being compared to a former operating point.

Claims

1. A method for detecting a fault in a rotating field machine having a motor connected to a frequency converter, in which current components are analysed at the frequency converter in a flux-based, particularly rotor-flux-based, coordinate system, a flux-forming current component (i_vekd) being subjected to a frequency analysis at the frequency converter in the flux-based, particularly rotor-flux-based, coordinate system, wherein a current operating point is detected at the frequency converter for at least one predetermined supply frequency (f_sp), said operating point being compared to a former operating point stored in a reference memory;

wherein at least one critical frequency (f_k) is calculated and the frequency spectrum is analysed at this critical frequency (f_k); and

wherein the critical frequency (f_k) of a stator fault is determined as

f_k=2·

f_sp

and of a rotor winding fault as

f_k=2(f_sp−

n·

p)

where;

f_sp is the supply frequency,

n is the rotor speed, and

p is the number of pole pairs.

2. The method according to claim 1, wherein the former operating point corresponds to a fault-free state of the machine.

3. The method according to claim 1, wherein a fast Fourier transform is used for the frequency analysis.

4. The method according to claim 3, wherein the fast Fourier transform is made during a time window of a predetermined length.

5. The method according to claim 4, wherein the supply frequency (f_sp) is kept constant during the time window.

6. The method according to claim 4, wherein a symmetric voltage is maintained within the time window.

7. The method according to claim 1, wherein the required values are obtained from operational data of the frequency converter.