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The use of alternating current machines of a simple construction with the squirrel cage rotor or the soft iron salient pole rotor as a car generator allows to increase a reliability of a generator and the maximum rotor rotation frequency as well in comparison with synchronous machines. The main feature of a car generator operation is a wide range of a rotation frequency change (five or six times). The use of alternating current machines aforementioned with the capacitor excitation is impossible, because it requires a capacitance value change in a wide range. In the paper presented the rotor excitation by passing current impulses through the stator winding over necessary periods of time is considered. The possibility of such an excitation is confirmed by the experiment. The single-phase generator with external rotor excitation is analysed on the basis of a digital model.

Always for means of test and diagnostics of car units are made great requirements. First of all there are technical, economic and ergonomic requirements, and also requirements of increased reliability, ecology and high operational qualities. The necessity of a measurement of the torque exists in many car test stands. In a number of stands as the load for an engine the electrical machines are used. Balance machines have the broadest application. Also the torque of the electrical machines is often measured approximately regarding the input current. Sometimes more complex estimations are applied.