| 摘要 |
PURPOSE:To safely operate a synchronous motor, by changing over both a rated field current limit portion and a field current limit portion greater than said rated field current limit portion by aiming at a fact that a heat characteristic of a field system of the synchronous motor is approximate 2.2 times as much as field currents and by mounting said field current limit portion besides said rated field current limit portion. CONSTITUTION:When a synchronous motor 1 is operated in value not more than rating (1F=1.0PU) within the tolerance of a heat characteristic (1F)<2.2> < (1.0PU)<2.2> of a field system, field currents detected by means of a direct current transformer 5 are input to a function generator 17 through a field current converter 16, and multiplied by approximate 2.2, and the output is input to a comparison amplifier 19. Said input is smaller than a set point of a reference set instrument 18 because field currents are not more than rated value, thus lmited signals are put out from the comparison amplifier 19 and applied to comparators 21, 23. The signals are compared with reference set points in the comparators, and field currents are controlled by the output, thus the motor can be operated even by field currents not less than rating within the tolerance of the heat characteristic of the field system of the synchronous motor. |
