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US6774664B2
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Method for automated measurement of the ohmic rotor resistance of an asynchronous machine
Assignee: Danfoss Power Electronics AS
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Filing: 2002-02-28
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Granted: 2004-08-10
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Expires: 2022-02-28
Abstract
Abstract Method of automated measurement of the ohmic rotor resistance (R r ) of an asynchronous machine ( 1 ) controlled via an inverter ( 8 ) while being acted upon by a non-rotating field, the method involving a. measuring the ohmic stator resistance (R s ), the leakage inductances (L σs , L σr ) and the main inductance (L m ) of the asynchronous machine, b. leading a testing signal (U sa ) being formed by a predetermined direct signal with a superimposed alternating signal corresponding approximately to the nominal slip frequency (f s ) of the asynchronous machine ( 1 ), c. measuring the amplitude and the phase (φ) of the phase signal (I sa ) resulting from the testing signal, and d. calculating the ohmic rotor resistance (R r ) from the measured values according to a) and c).
Inventors
- 👤 Jens Godbersen
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 16:06
CPC Classifications
G; G01; G01R; G01R31/00; G01R31/34; G01R27/00; G01R27/02; G01R31/346
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
148 words
Method for automated measurement of the ohmic rotor resistance (R r ) of an asynchronous machine controlled via an inverter while being acted upon by a non-rotating field, the method comprising a. measuring the ohmic stator resistance (R s ), the leakage inductances (L σs , L σr ) and the main inductance (L m ) of the asynchronous machine, b. applying a testing signal (U sa ) consisting of a predetermined direct signal with a superimposed alternating signal to a phase winding (a) of the asynchronous machine, the frequency of the alternating signal corresponding approximately to a nominal slip frequency (f s ) of the asynchronous machine, c. measuring the amplitude and the phase (φ) of the phase signal({overscore (I)} sa ) resulting from the testing signal, and d. calculating the ohmic rotor resistance (R r ) from the measured values according to steps a) and c).
Claim 2
Dependent Claim
148 words
Method for automated measurement of the ohmic rotor resistance (R r ) of an asynchronous machine controlled via an inverter while being acted upon by a non-rotating field, the method comprising a. measuring the ohmic stator resistance (R s ), the leakage inductances (L σs , L σr ) and the main inductance (L m ) of the asynchronous machine, b. applying a testing signal (U sa ) consisting of a predetermined direct signal with a superimposed alternating signal to a phase winding (a) of the asynchronous machine, the frequency of the alternating signal corresponding approximately to a nominal slip frequency (f s ) of the asynchronous machine, c. measuring the amplitude and the phase (φ) of the phase signal({overscore (I)} sa ) resulting from the testing signal, and d. calculating the ohmic rotor resistance (R r ) from the measured values according to steps a) and c).
Claim 3
Dependent Claim
46 words
Method according to claim 1 , in which an ohmic rotor resistance (R′ r ) transformed to the stator side is determined first, and the actual ohmic rotor resistance (R r ) is calculated by means of the measured values according to steps a) and c).
Claim 4
Dependent Claim
25 words
Method according to claim 1 in which the frequency (f s ) of the alternating signal is in the range from 1 to 8 Hz.
Claim 5
Dependent Claim
37 words
Method according to claim 1 in which the direct signal is a direct voltage which generates a direct current having an amplitude of less than half a nominal magnetising current (I mn ) of the asynchronous machine.
Claim 6
Dependent Claim
86 words
Method according to claim 4 , in which the direct current is such that the dynamic main inductance (L Dm ) is approximately equal to the static main inductance (L m ) of the asynchronous machine, whereby the dynamic main inductance can be expressed by the equation L D m = L m I m · I m + L m In which L Dm is the dynamic main inductance, L m the static main inductance and I m the magnetising current.
Claim 7
Dependent Claim
51 words
Method according to claim 1 in which the testing signal is a phase voltage (U sa ) having a reference (U ref ) set on the basis of a previously measured characteristic, stored in a memory, the characteristic describing the relation between the phase current (I sa ) and the reference.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2007-08-10 | 2008-02-09 | 2008-08-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2011-08-10 | 2012-02-09 | 2012-08-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2015-08-10 | 2016-02-09 | 2016-08-10 | $7700.00 | Window Closed / Lapsed |