| 摘要 |
<p>PURPOSE:To protect a motor from overvoltage without using a detector for high voltage by interrupting a brake resistor connected in parallel with an armature winding for the main motor when the terminal voltage value of the main motor at the time of rheostatic brake-operation exceeds a threshold value. CONSTITUTION:A differential output DELTAif between a differential output between a field current if and an output if0 from a reference pattern setter 21 and an output from a field-ratio abnormal signal generator 28 is transmitted over a field-converter phase angle setter 24. When a differential output DELTAia between the multiplied value iaomega of the field current if and an output Kf from a field-ratio pattern generator 25 and armature current ia takes a positive number and continues for several sec., on the other hand, a rheostatic brake abnormal signal BFD is output, and a brake resistor is interrupted. When a differential output between a field current pattern ifm to motor speed V set on the basis of an overvoltage limit and the field current if takes a positive number, the rheostatic brake abnormal signal BFD is output, and the brake resistor is interrupted.</p> |
