Instrumentation, testing, and analysis of electric machine rotor steady-state heating

IEEE International Conference on Electric Machines and Drives, 2005.

Habetler

Harley

2005

Thermal models are often used in motor overload protection relays to predict rotor temperature. Under impaired cooling conditions, the parameters in the thermal models need to be tuned accordingly to reflect changes in the motor cooling capability.The tuning process requires accurate rotor temperature as a reference signal. This reference signal is estimated from the rotor resistance based on the equivalent circuit of the induction machine; however, it is often corrupted by noise due to the asymmetry in the power supply. A detailed analysis of the trajectories of the voltage and current space vectors in the synchronously rotating d-q reference frame is presented in this paper. The axis misalignment due to the negative sequence space vectors is identified as the major source of noise. Based on this analysis, a robust and efficient rotor temperature estimator is proposed in this paper. A digital positive sequence waveform synthesizer is designed to help align the d-axis with the positive sequence current space vector. Then, the induction machine positive sequence equivalent circuit is used to give a reliable estimate of the rotor resistance, which in turn yields the rotor temperature. This estimated temperature is subsequently used to tune the parameters of the rotor thermal model online. The proposed rotor temperature estimator is validated by experiments. The estimated rotor temperature is demonstrated to be sufficiently accurate, and is therefore appropriate to be used as a reference signal for the online tuning of the rotor thermal model parameters. The thermal model built from this reference signal is able to track the rotor temperature accurately under impaired cooling conditions.

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A robust rotor temperature estimator for induction machines in the face of changing cooling conditions and unbalanced supply

IEEE International Conference on Electric Machines and Drives, 2005.

Habetler

Harley

2005

“…The complex reference signal, y n , is the product of a complex incident signal, x n−1 , and a complex exponential of an iterative phase estimate, φ n (in radians), y n = x n−1 ·exp( j·φ n ) (5) where the complex incident signal x n−1 is the complex primary signal x n delayed by one sample, as denoted by z −1 in Fig. 1.…”

Section: Phase Discriminatormentioning

confidence: 99%

“…This approach is suitable for small-to medium-sized grid-connected induction motors because it circumvents problems associated with direct rotor temperature measurements, which usually involve expensive instruments or dedicated wiring back to a motor control center [5]. It is also capable of giving temperature estimates tailored to a specific motor's cooling capability [6].…”

Section: Introductionmentioning

confidence: 99%

Supply frequency tracking in resistance-based induction motor rotor temperature estimation

2012 IEEE Energy Conversion Congress and Exposition (ECCE)

Colby

Turner

2012

In resistance-based rotor temperature estimation schemes, a rotor temperature is derived from a resistance quantity based on an induction motor equivalent circuit model. This temperature is susceptible to fluctuations in the motor's supply frequency. In this paper, a complex adaptive phase discriminator is proposed to track supply frequency fluctuations for grid-connected induction motors. A frequency-selective digital filter is applied to attenuate harmonics and interferences in a complex voltage vector.The complex adaptive phase discriminator then iteratively adapts the phase of a complex exponential to align a complex reference signal with a complex primary signal. The power grid's supply frequency is directly estimated from the adapted phase on a sample-by-sample basis. Experimental results demonstrate that the proposed complex adaptive phase discriminator helps produce rotor temperature estimates with an increased accuracy.

“…The slip frequency is often resolved from rotor slot harmonics by applying spectral estimation techniques to acquired current samples [4]. This approach Manuscript is suitable for small-to medium-sized grid-connected induction motors because it circumvents problems associated with direct rotor temperature measurements, which usually involve expensive instruments and dedicated wiring back to a motor control center [5]. It is also capable of giving temperature estimates tailored to a specific motor's cooling capability [6].…”

Section: Introductionmentioning

confidence: 99%

Supply Frequency Tracking in Resistance-Based Induction Motor's Rotor Temperature Estimation

IEEE Trans. on Ind. Applicat.

Colby

Turner

2014

In resistance-based rotor temperature estimation schemes, a grid-connected induction motor's rotor temperature is derived from a resistance quantity based on an equivalent circuit model. This temperature is susceptible to fluctuations in the motor's supply frequency. In this paper, the relationship between supply frequency fluctuations and accuracy in resistance-based rotor temperature estimates is analyzed, and a complex adaptive phase discriminator is proposed to track the supply frequency fluctuations for grid-connected induction motors. A complex voltage vector is constructed from polyphase voltage measurements and passed through a frequency-selective digital filter to attenuate harmonics and interference. The complex adaptive phase discriminator then operates on the filtered voltage signal, iteratively adapting a complex reference signal's phase to align it with the filtered voltage signal. The power grid's supply frequency is directly estimated from the adapted phase on a sample-by-sample basis. Experimental results demonstrate that the proposed complex adaptive phase discriminator helps produce rotor temperature estimates with increased accuracy.