| 摘要 |
PURPOSE:To reduce loss due to line resistance by determining the starting point of field control by a speed signal. CONSTITUTION:When a motor-voltage signal is smaller than a field-weakening point setting signal set by a variable resistor RH1, an output from an amplifier OA1 is brought to a negative value, and interrupted by a diode D1. Consequently, field currents only corresponding to a signal set by a variable resistor RH2 for setting a maximum field flow. When the motor-voltage signal is made larger than the field-weakening point setting signal, the output from the amplifier OA1 works so as to deny the maximum field signal, and field currents are reduced. On the other hand, an amplifier OA3 extracts a speed signal larger than a value set by a variable resistor RH4 for setting a correction point, and applies it as an input signal to the amplifier OA1. Accordingly, motor voltage in a field control region can be kept at a value as high as possible, thus reducing power loss by line resistance in a motor. |
