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Whenever you start a big heavy electric motor, you need to start it slowly to prevent the rotor overheating and drawing an enormous current or to prevent damage to the load it is driving. When the windings of a 3-phase motor are connected in STAR the current is reduced by a factor of (one over root three) times (the normal running current that is taken when it is connected in DELTA.)
Once the motor picks up speed, the connection is changed to DELTA so that the motor runs at full speed and torque from then on. It's a bit like using the gears of an automobile.
For more information, see the answers to the Related Questions shown below.
Wiki User
∙ 14y ago
Wiki User
∙ 10y agoIf the delta magnetic starter pulls in then there is a problem in the delta windings of the motor. If the magnetic starter does not pull in then there is a problem in the star delta timing relay. Check the timer relay for voltage output to the delta magnetic after the completion of the timing interval.
Wiki User
∙ 12y agoA motor will run at the same speed in star and delta formation, the difference is related to torque capability and to an extent power drawn from the system. A star formation provides high torque capability of the motor ideal for starting, but consumes more power than delta under torque loading. A Delta configuration is better for continuous running where negligable torque differences are encountered as this configuration does not tolerate torque changes well and the motor can stall under high torque load, due to low torque loadings of this configuration generally less power is drawn than in star configurations.
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Why motor is connected in star connection first in star delta starter?
To use a star delta starter, the motor must be a three phase six wire motor. The extra wires out are the wires that are usually terminated in the motor housing as the star point. The starter, when energized, brings the star contactor in and closes the star point coil ends. An external timer times out after the motor gets up to speed in the star connection and drops the star contactor and closes the delta contactor. When in the delta connection the motor coils are then paralleled to allow the motor to run at full voltage.
What is the starting sequence of a star-delta starter?
This is the schematic for the starter. K1T is a timer. Initially KM1 and KM3 are closed to start the motor. Then KM2 is closed and KM1 is opened to run the motor This is the equivalent ladder logic using relays and timers.
Why does my star delta motor run at very high amps in delta and eventually trips on overload after changing the overload protection device.It should normally run at 25amp in delta but runs at 170 amps?
THE FIRST THING IS TAKE THE READING OFF LOAD AND SEE IF THEY ARE BALANCED. HAS THE MOTOR BEEN RECENTLY REWOUND? GET A MOTOR REPAIR COMPANY TO LOOK AT THE MOTOR AND SEE IF IT HAS BEEN WOUND CORRECTLY. IF THE STAR-DELTA WORKS CORRECTLY IT SHOULD START IN STAR FOR ABOUT FIVE TO TEN SECONDS AND GO INTO DELTA THIS IS DEPENDANT ON THE STARTING CURRENT THE MANUFACTURE OF THE SWITCH AND THE APPLICATION. CHECK ALL THREE PHASES ARE BALANCED AND IF THEY ARE THE MOTOR WINDINGS MAY NOT BE CORRECTLY WOUND. SOME HAVE STAR CONNECTIONS BUILT IN.LOOKING AT THE AMPERAGE THE LOAD REQUIREMENT IS ONLY A FRACTION OF WHAT YOU ARE GETTING SO IT LEAVES ONLY TWO THINGS I......MOTOR FAULT 2.....WHAT EVER THE MOTOR IS DRIVING IS PUTTING A MASSIVE PRESSURE ON THE MOTOR CAUSING IT TO OVERLOAD.
Can you run a star motor in delta?
Delta motors should have more starting current than Wye (Star) motors because Delta motors have two windings to take current per phase -- they are wired Phase to Phase. Star motors have only one winding per phase -- they are wired Phase to Neutral.
What is the time required from changing star to delta?
The change over time will vary with the type of motor, size of motor and the connected load to the motor. The time should be adjusted so that the motor is up to speed and stabilized at the star speed. It is at this point that the change to delta should take place. One thing to note is, do not leave the motor running is the star position any longer that it needs to.
What are the advantages of using star connection?
The inrush current is reduced. This is the reason for star delta starters. Motor starts on star and after about 10 to 15 seconds, depending on the load of the motor, it switches to a delta configuration to run.
Should a star-delta motor be supplied wye or delta power?
A star-delta motor should be supplied star-delta.Wye is simply another name for star. Star-delta motors use a star or wye configuration to start, and a delta configuration to run. This reduces the voltage on the windings during the high current starting time.
Can you run a star delta motor on just the star connection?
Yes, but you won't get full power. You'll only get half power.
What will happen when motor is connected to star?
If the motor is designed to operate on star (wye) then it is fine. If it is designed to operate on delta, then you need to consider that star will present lower operating voltage than delta, and that might damage the motor.Some motors are designed to start on star and run on delta. Usually, this applies to larger motors, and cannot be overlooked. If there are only three wires (ignoring chassis ground), then the motor is intended for delta. If there are only four wires, the the motor is intended for star. If there are six wires, then the motor is intended for star-delta. Of course, the starter controls could be integrated with the motor, so it is best to consult the name plate and operate the motor exactly as it was designed.
What can be done with the help of star and delta conversions?
Using star delta method of wiring you can run high rated motor with out any high starting current. Star connection can provide 3 phase power as well as single phase load
Why motor is connected in star connection first in star delta starter?
To use a star delta starter, the motor must be a three phase six wire motor. The extra wires out are the wires that are usually terminated in the motor housing as the star point. The starter, when energized, brings the star contactor in and closes the star point coil ends. An external timer times out after the motor gets up to speed in the star connection and drops the star contactor and closes the delta contactor. When in the delta connection the motor coils are then paralleled to allow the motor to run at full voltage.
Why is the automatic star to delta starter tripping?
The only thing that will trip the starter, is the load of the motor. Check the motor leads to make sure you have not crossed them over coming from the motor junction box. If the motor current is normal nameplate full load amps when run across the line then reduce the timing of the timer on the switch over from star to delta.
What is the starting sequence of a star-delta starter?
This is the schematic for the starter. K1T is a timer. Initially KM1 and KM3 are closed to start the motor. Then KM2 is closed and KM1 is opened to run the motor This is the equivalent ladder logic using relays and timers.
What supply is needed to run a 22kw 3ph motor?
question is incomplete, I think you ask how much current consumed by this motor. for starting this motor we need a star/delta starter and a three phase supply.
Why does my star delta motor run at very high amps in delta and eventually trips on overload after changing the overload protection device.It should normally run at 25amp in delta but runs at 170 amps?
THE FIRST THING IS TAKE THE READING OFF LOAD AND SEE IF THEY ARE BALANCED. HAS THE MOTOR BEEN RECENTLY REWOUND? GET A MOTOR REPAIR COMPANY TO LOOK AT THE MOTOR AND SEE IF IT HAS BEEN WOUND CORRECTLY. IF THE STAR-DELTA WORKS CORRECTLY IT SHOULD START IN STAR FOR ABOUT FIVE TO TEN SECONDS AND GO INTO DELTA THIS IS DEPENDANT ON THE STARTING CURRENT THE MANUFACTURE OF THE SWITCH AND THE APPLICATION. CHECK ALL THREE PHASES ARE BALANCED AND IF THEY ARE THE MOTOR WINDINGS MAY NOT BE CORRECTLY WOUND. SOME HAVE STAR CONNECTIONS BUILT IN.LOOKING AT THE AMPERAGE THE LOAD REQUIREMENT IS ONLY A FRACTION OF WHAT YOU ARE GETTING SO IT LEAVES ONLY TWO THINGS I......MOTOR FAULT 2.....WHAT EVER THE MOTOR IS DRIVING IS PUTTING A MASSIVE PRESSURE ON THE MOTOR CAUSING IT TO OVERLOAD.
Can you run a star motor in delta?
Delta motors should have more starting current than Wye (Star) motors because Delta motors have two windings to take current per phase -- they are wired Phase to Phase. Star motors have only one winding per phase -- they are wired Phase to Neutral.
What is the time required from changing star to delta?
The change over time will vary with the type of motor, size of motor and the connected load to the motor. The time should be adjusted so that the motor is up to speed and stabilized at the star speed. It is at this point that the change to delta should take place. One thing to note is, do not leave the motor running is the star position any longer that it needs to.
