It also eliminates rush current during starting of motor. Hence, available power (single-phase) is given to VFD, and output (three-phase power) of VFD is used as input of a three-phase motor. And the frequency of the three-phase output is adjusted by VFD. Again, it converts DC supply into a three-phase AC supply. VFD converts single-phase supply into DC by rectifying. In this case, an available single-phase supply is given as input to the VFD. This method is best to operate a three-phase induction motor on a single-phase supply. This device allows the motor to operate efficiently over varying load conditions. VFD adjusts the input current of a motor according to demand (load). It is a device that is used to control the motor (adjustable speed on running). What happens to the 3-Phase Motor When 2 Out of 3 Phases are Lost?.What happens to the 3-Phase Motor When 1 Out of 3 Phases is Lost?.This will reduce the life span of the motor. In this method, the loading effect is continuously in two phases.It is not suitable for continuous running applications. This method can be used for a temporary purpose.The output power of the three-phase induction motor is reduced by 2/3 rd of full load power.The circuit diagram of this arrangement is shown in the figure below. The start capacitor is 4 to 5 times higher capacity compared to a running capacitor. In some arrangements, two capacitors are used one for starting and the second for running. This method is also known as the static phase converter method or phase-shifting method or rewinding method. The net output or efficiency of the motor is reduced 2/3 rd of its rated capacity. Once the three-phase induction motor started on a single-phase supply, it continuously runs on reduced capacity. Similar to this principle, we can use three-phase winding of a three-phase induction motor and shift one winding using a capacitor or inductor. Instead of a starting winding, a capacitor or inductor is also used to create phase displacement. In a single-phase induction motor, an extra winding is used to create a phase shift. And in this case, initial torque (starting torque) is not produced. But in the case of a single-phase induction motor, a pulsating magnetic field is induced. When we supply three-phase AC power to the stator of the three-phase induction motor, a balanced time-varying 120˚ apart rotating magnetic field is produced. In this article, we will discuss each method in brief.
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