Calculation of Braking Torque Curve of Induction Machine Under DC Current Injection

Abstract

Induction machines have widely been used in many industrial factories. In the case of emergency, braking torque is always needed. One of the simple braking methods is dc current injection. In order to stop the machines in efficient manner with a desired operating time, their accurate speed-torque curves in the braking zone are often required. It has been reported in the open literature that machine’s braking torque curve calculations have not yet been fully completed so far due to an ignorance of their nonlinear effects. Thus, this paper presents an extension to the braking torque-speed curve calculation of induction machines under dc injection braking. The saturation of mutual and rotor-leakage reactances as well as the slip-dependent rotor resistance are entirely taken into account. To validate the proposed model, the braking torque-speed curves between calculation and laboratory measurement are compared. A good agreement is observed in the satisfactory manner. Moreover, an application of the proposed torque-speed curve in determining the machine’s braking time is demonstrated. An acceptable accuracy in the breaking times between calculation and measurement approaches is shown.