To limit the starting current surge, large induction motors are started at reduced voltage and then have full supply voltage reconnected when they run up to near rotated speed.
Working Principle of Star-Delta Starter
This is the reduced voltage starting method. Voltage reduction during star-delta starting is achieved by physically reconfiguring the motor windings as illustrated in the figure below. During starting the motor windings are connected in star configuration and this reduces the voltage across each winding 3. This also reduces the torque by a factor of three.
Scheme – Working Principle of Star-Delta Starter
After a period of time the winding are reconfigured as delta and the motor runs normally. Star/Delta starters are probably the most common reduced voltage starters. They are used in an attempt to reduce the start current applied to the motor during start as a means of reducing the disturbances and interference on the electrical supply.
Terminal Connections in Star and Delta Configurations:
L1, L2 and L3 are the 3-phase line voltages, which are given to primary contactor. The main motor coils are U, V and W is shown in figure. In star mode of motor windings, the primary contactor associate the mains to essential winding terminals U1, V1 and W1.the star contactor shorts the auxiliary winding terminals U2, V2 and W2 as indicated in figure. Notwithstanding when the primary contactor is shut supply arrives at terminals A1, B1, C1 and consequently the motor windings are energized in star-mode.
To limit the starting current surge, large induction motors are started at reduced voltage and then have full supply voltage reconnected when they run up to near rotated speed.
Working Principle of Star-Delta Starter
This is the reduced voltage starting method. Voltage reduction during star-delta starting is achieved by physically reconfiguring the motor windings as illustrated in the figure below. During starting the motor windings are connected in star configuration and this reduces the voltage across each winding 3. This also reduces the torque by a factor of three.
Scheme – Working Principle of Star-Delta Starter
After a period of time the winding are reconfigured as delta and the motor runs normally. Star/Delta starters are probably the most common reduced voltage starters. They are used in an attempt to reduce the start current applied to the motor during start as a means of reducing the disturbances and interference on the electrical supply.
Terminal Connections in Star and Delta Configurations:
L1, L2 and L3 are the 3-phase line voltages, which are given to primary contactor. The main motor coils are U, V and W is shown in figure. In star mode of motor windings, the primary contactor associate the mains to essential winding terminals U1, V1 and W1.the star contactor shorts the auxiliary winding terminals U2, V2 and W2 as indicated in figure. Notwithstanding when the primary contactor is shut supply arrives at terminals A1, B1, C1 and consequently the motor windings are energized in star-mode.
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