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In this paper, a self-excited induction generator that can act as an electric retarder is presented, and an effective control method and circuit for enacting it are proposed. To control braking torque, the equivalent circuit parameters of the retarder are changed by switching the proposed circuit. Even though the retarder is a high-voltage high-current ac machine, it uses readily available and inexpensive components including a low-voltage high current-rating MOSFET, diodes, and a polarity capacitor. Dynamo test results show that the proposed circuit and method is effective.

A self-excited induction generator (SEIG) can be a candidate for isolated applications because it does not require any external exciting power but can independently generate electricity. It is also a good candidate for auxiliary brakes in heavy vehicles for several reasons. First, the power efficiency in a brake system is not important as compared with motors or generators. Second, an SEIG can be controlled by a simple electrical circuit. Third, it can be used for regenerative braking. Finally, it is very robust. In this paper, an auxiliary brake for heavy vehicles is proposed by adapting an SEIG and its analog control circuit. The brake structure is the same as that in conventional eddy current brakes but operates as an SEIG. The suggested control circuit does not adopt an electric controller unit but only consists of simple electric devices. A miniature model was designed and manufactured, and the experimental results using the prototype verify that the proposed brake system, including the controller, is very useful.

In this paper, a regenerative electromagnetic brake, which has the same structure as conventional electromagnetic brakes and the same principle as self-excited induction generators, is introduced, and a miniature model is designed. The most important part of the design stage is to choose proper equivalent circuit parameters for self-excitation within a given operating speed range. This paper describes a 3-D map, called a CN-map, that consists of the rotating speed, capacitance, and stator resistance to verify the possibility of self-excitation during the design stage. A miniature model is designed using the map, and the experimental results obtained with the miniature model confirm the feasibility of the design process.