Determination Of Stray Load Losses Research Articles

Comparison of Different Evaluation Methods to Determine Stray Load Losses in Induction Machines With Eh-Star Method

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> The eh-star method is a simple and economical alternative test for stray-load-loss assessment in induction machines, also for higher efficiency above 96%. It is an asymmetrical circuit where two machine phases are connected in parallel through an auxiliary <emphasis emphasistype="boldital">ohmic</emphasis> resistance <formula formulatype="inline"><tex Notation="TeX">$R_{\rm eh}$</tex></formula> without coupling of the machine and without needing any dynamometer. This resistance shall be adjusted, so that the positive sequence current <formula formulatype="inline"><tex Notation="TeX">$I_{1}$</tex></formula> stays below 30% of negative sequence current <formula formulatype="inline"><tex Notation="TeX">$I_{2}$</tex></formula>. If this pure “<emphasis emphasistype="boldital"> ohmic</emphasis>” resistance is not available, the eh-star measurement can be done with an impedance <formula formulatype="inline"><tex Notation="TeX">$\underline{Z}_{\rm eh}$</tex></formula>, preferably <emphasis emphasistype="boldital">ohmic</emphasis> inductive. The determination of stray load losses must be done from the measured losses by decomposition into positive and negative sequence losses. Negative sequence losses at slip <formula formulatype="inline"><tex Notation="TeX">$2 - s \approx 2$</tex></formula> correspond to stray load losses similar to the standardized reverse-rotation test (RRT). For this evaluation, the phase angles of measured currents and voltages must be known. This can be done by calculation with three different methods A, B, and C, which yield identical results for ideal <emphasis emphasistype="boldital">ohmic</emphasis> resistance <formula formulatype="inline"><tex Notation="TeX">$R_{\rm eh}$</tex></formula>. Method A is only useful for an <emphasis emphasistype="boldital">ohmic</emphasis> resistance <formula formulatype="inline"><tex Notation="TeX">$R_{\rm eh}$</tex> </formula> for determination of loss separation. Method B is based on the measured two line-to-line motor-input-power values <formula formulatype="inline"><tex Notation="TeX">$P_{{\rm e}, {\rm in}\_{\rm UV}}$</tex></formula> and <formula formulatype="inline"><tex Notation="TeX">$P_{{\rm e}, {\rm in}\_{\rm WV}}$</tex></formula>. Instead of <formula formulatype="inline"><tex Notation="TeX">$R_{\rm eh}$</tex></formula>, also an impedance <formula formulatype="inline"> <tex Notation="TeX">$\underline{Z}_{\rm eh}$</tex></formula> (inductor, capacitor, or resistor) may be used. Method C is similar to method B, but only the measured total motor input power <formula formulatype="inline"><tex Notation="TeX">$P_{{\rm e}, {\rm in}}$ </tex></formula> is needed. A comparison of evaluated stray load losses with the three evaluation methods is given with theoretical examples and measurements. This is compared to stray load losses and measured with RRT and input–output method according to IEEE-112. </para>

Determination of stray load loss in D-C machines

A SPECIALLY DEVISED METHOD using the Blondel load-back principle of loss measurement has been employed to measure the stray load loss in d-c machines. An inherently accurate value of the loss is obtained by measuring it as two separate components by a method which is direct and easy to perform.

Determination of Stray Load Loss in D-C Machines [includes discussion

A SPECIALLY DEVISED METHOD using the Blondel load-back principle of loss measurement has been employed to measure the stray load loss in d-c machines. An inherently accurate value of the loss is obtained by measuring it as two separate components by a method which is direct and easy to perform.

Reverse-Rotation Test for the Determination of Stray Load Loss in Induction Machines

VARIOUS methods for the accurate determination of stray load loss in induction machines have been devised in recent years. Also older methods have been improved and developed as the nature of the loss has become better understood. The employment of different methods of testing on a given machine seldom shows complete agreement in results, due to minor discrepancies and inaccuracies inherent in the methods themselves. Another difficulty is that all of the plans proposed to date require a high degree of skill and experience on the part of the testing technician. Thus industry today finds itself in need of a test which will give highly accurate results and at the same time be simple and easy to perform. The purpose of this paper is to describe a new method of testing — termed the “reverse-rotation test” — which will more nearly meet these requirements. The theoretical basis and the assumptions involved are discussed. Tests to determine the accuracy of the method have been made on two squirrel-cage motors of somewhat different characteristics by various methods of testing. The results of these investigations are described and curves are given showing the degree of exactness obtained. While the method includes assumptions regarding compensating effects involving minor components of the loss, its over-all accuracy for the motors tested is shown by comparison with the values obtained by other methods having high precision.

Reverse-rotation test for the determination of stray load loss in induction machines

Reverse-rotation test for the determination of stray load loss in induction machines

D-C machine stray-load-loss tests

Two test methods for the determination of stray load losses in d-c machines are described. Application of the loading-back principle permits measurements to a high degree of accuracy. A technique is developed for stabilizing no-load losses so that consistency of results is improved. Results of tests of several machines are presented, together with an analysis of the relation of loss to operating conditions of the machine.

D-C Machine Stray-Load-Loss Tests

Two test methods for the determination of stray load losses in d-c machines are described. Application of the loading-back principle permits measurements to a high degree of accuracy. A technique is developed for stabilizing no-load losses so that consistency of results is improved. Results of tests of several machines are presented, together with an analysis of the relation of loss to operating conditions of the machine.

Stray load loss tests on induction machines-II

A new test method is described for the determination of stray load loss in induction machines. By application to given machines, this method is shown to have an exceptionally high degree of accuracy. Values of stray load loss for the same machines are obtained by other recognized methods and results compared. Results support the validity of a previously described1 "belted load-back method."

Stray load loss tests on induction machines — II

A new test method is described for the determination of stray load loss in induction machines. By application to given machines, this method is shown to have an exceptionally high degree of accuracy. Values of stray load loss for the same machines are obtained by other recognized methods and results compared. Results support the validity of a previously described1 belted load-back method.