This paper outlines a set of useful calculations and design guidelines for motor temperature rise prediction. The steady-state analysis is presented, allowing a general view about the expected temperature rise in the stator winding. For transient conditions, the starting and stall phenomena are modeled considering the factors that are often neglected: the skin effect and the heat exchange from the bars to the tooth. The end ring temperature rise is assessed. The accurate temperature rise calculation is critical for several reasons: to control the peak temperature for hazardous locations, to predict the fatigue under the heating-up and cooling-down processes, to calculate the number of consecutive starts, and to establish a safe stall time.

Use of Thermal Network on Determining the Temperature Distribution Inside Electric Motors in Steady-State and Dynamic Conditions

A new brushless and permanent magnet less synchronous generator is reported in this work. Contrary to traditional brushless synchronous generators that use an extra machine along with rotating diode rectifier, the proposed machine houses the main and the exciter machine in the same frame. Thus the size, cost, and efficiency of the proposed system are expected to be more competitive. Magnetic decoupling between two windings wound for different number of poles is exploited to create such generators. Two synchronous machines are connected in cascade and housed in the same frame with the armature of the exciter machine put on the rotor and field on the stator. The main machine is a standard synchronous generator. For preliminary investigations, an experimental machine is made having four poles and six poles for main machine and exciter machine, respectively. While the armature of the exciter machine can be wound for different number of phases, a three-phase winding is considered that is fed to rotating rectifier. The output of the rectifier provides field excitation to the main synchronous machine. Extensive simulation studies are carried out using MAXWELL 2D and matlab /Simulink. Experimentations conducted on the laboratory prototype match well with the simulations confirming the effectiveness of the proposed generation system.

Synchronous Generator With Embedded Brushless Synchronous Exciter

This paper investigates electrical breakdown of interconductor insulation, which presents an obstacle to the increase of the rated voltage of electrical machines as a means to improve efficiency of electrical energy exploitation. We have investigated a large number of samples searching for weak points in interconductor insulation along the coil of a high voltage asynchronous machine. The experiments were performed on lacquer-glass-glass-lacquer conductor insulation. Location of weak points and breakdown voltage levels have been determined.

Effect of Insulation Construction Bending on Stator Winding Failure

This paper outlines a set of useful calculations and design guidelines for motor temperature rise prediction. Steady state analysis is presented, allowing a general view about the expected temperature rise in the stator winding. For transient conditions, starting and stall phenomena are modeled considering factors that are often neglected: the skin effect and the heat exchange from bars to the tooth. End ring temperature rise is assessed. Accurate temperature rise calculation is critical for several reasons: to control the peak temperature for hazardous locations, to predict the fatigue under the heating up and cooling down processes, to calculate the number of consecutive starts and to establish a safe stall time.

Use of thermal network on determining the temperature distribution inside electric motors in steady state and dynamic conditions

This paper compares different squirrel cage designs under starting and running performance. Inrush current, torque, stall time, maximum number of consecutive starts, efficiency, power factor, critical speed and cage stress are discussed along the paper while considering aluminum and a copper alloy cages. For the sake of comparison two machines were selected to perform the study — one 4-pole 6500 HP and one 18-pole 3500 HP. In addition, procedures of repairing fabricated copper and aluminum cages are discussed.

M. G. Say

Papers

The performance and design of alternating current machines; transformers, three-phase induction motors and synchronous machines,