Concrete vibrator
 A concrete vibrator is disclosed in which a sensorless semiconductor motor is employed for driving an exciter. The sensorless semiconductor motor has an arrangement in which the rotational position of the permanent magnet rotor is sensed through utilization of a voltage which is induced from three-phase stator windings, i.e. a voltage which is induced according to the magnetic flux distribution in the gap and varies its frequency with the rotation speed alone instead of by using the Hall element which is readily damaged by vibration and heat, that is, seriously poor in environmental resistance. Further, the sensorless semiconductor motor is arranged so that the current supply to the stator winding is placed under control of a semiconductor inverter which is controlled by a PWM or PAM system. 
Sinano Electric Co., Ltd. Mikasa Sangyo Kabushiki Kaisha
E H
E04G H02P
inventional inventional
Kenji Isao Kazuo Akinobu
Yoshida Baba Matsushita Shionoya