| 摘要 |
PURPOSE:To enable a frequency of an electric motor to be controlled before applying a countermeasure against an over-current and also enable a rising speed of a freezing cycle to be increased by a method wherein a value of primary current after a specified time is estimated in view of a value of a primary current sensor and is compared with a predetermined current value to correct a frequency. CONSTITUTION:A signal from a primary current sensor 14 of an electric motor is inputted to a current differentiator 16 so as to calculate a difference DELTAI1 of a primary current value before a specified time of t of a timer 17. A sum of an estimated primary current I measured by the current differentiator 16 and the difference DELTA1 is outputted to a current width discriminating means 15. When an estimated current value I+ DELTAI is lower than a lower value 11 of a current width, +1 is outputted to an operating speed retainer 10; when it is higher than a high value I2, -1 is outputted to the operating speed retainer 10; and when it is less than the current width, a value of 0 is outputted to the operating speed retainer 10. The operating speed retainer 10 causes a variation in speed of a set value KDELTATHz corresponding to a temperature difference DELTAT outputted from the weighted difference sensor 5 to be KDELTATHz + or -DELTAHz when a signal from the discriminator 5 is + or -1, and then outputted to an operating controller 12 for an electric motor.
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