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It does not matter to the motor, just as long as the three phase voltage is what the motor specification requires.

HOWEVER..... While the motor will run in either star or delta, it will draw 3 times as much current in delta as it does in star, and will develop 3 times more torque (and power) in delta compared to star.

3 phase motors are often started in star, as it draws less current and is less likely to blow fuses, damage contacts and upset the supply system due to voltage drops. When the motor is near full speed, the motor is switched to delta connection for full power. This is called star-delta starting, and is suitable for light, low inertia loads such as fans or pumps. Because of the motor's reduced startup torque, it shouldn't be used for compressors, machines with heavy flywheels, or machines that come onto load before they reach full speed. Motors designed for star-delta starting will have 6 live terminals in their connection box.

Let's get a little bit technical. In star, each winding has L-N voltage across it (about 58% of the L-L voltage applied when in delta) - in Australia, our voltage from the active (live wire) to the neutral (return wire) is 230 volts, and the voltage from one active to another active is 400 volts. (230 / 400 is about 0.58, or 58%. and 400 / 230 is 1.73 or 173%). Connecting a motor in star puts 230 volts across each winding, and connects ONE winding to each supply phase. when running, it draws (say) 10 amps, and develops about 6 kW / 8HP. In delta, each winding has 400 volts across it, and each supply line powers 2 windings, so the current increases by 1.73 (400 volts compared to 230 volts) and again by 1.73 (2 windings on a 3 phase system draw 1.73 times more current than one winding.) 1.73 squared is 3 - so in delta, the motor draws 3 times more current (30 amps), and delivers 3 times more power (18kW / 24HP).

Some motors are designed to be operated ONLY in star - they may have a label advising you of this, or they may have only one value of voltage and current on the nameplate. They will also usually have only 3 terminals inside the connection box. If you suspect that the motor is 'star only', but want to make sure, connect the motor in delta, and check the running current as soon as the motor is up to speed; if it is drawing more than the nameplate current, or the motor is noisy in delta, but not in star, stop the motor immediately and reconnect it in star, or the motor WILL burn out very quickly.

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โˆ™ 2011-02-15 18:34:52
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Q: Should a 3 phase motor run on star or delta?
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Related questions

Which motor have more staring current star or 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.

Star delta starter for 3 phase induction motor?

how will you start 3phase inuction motor using star delta stater

When is a motor in star or delta connection?

That would happen when a three-phase motor is used. It can be connected in star or delta dependig on the manufacturers' instructions.

In a star-delta starter what could be the problem if the motor does not rotate in star but rotates in delta?

One of the three phase contacts in the star contactor could be burned open or just open not allowing the motor to start because of a single phase condition. The time interval between star and delta connections could be small enough that the motor heaters will not catch the single phase condition and trip. When the motor goes into delta (which is now across the line starting) all of the three phase contacts in the contactor close and the motor starts.

How star delta motor run?

star delta motors start as a Y for 3 phase so the windings that normally see 480 volts see 277V a relay switches to delta then it runs as a normal delta motor the reduces the starting current by about 60% for 3 phase

How do you wire a three phase motor with two speed?

Star and delta connection

Explain the operation of a 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.

IWant to see the connection of the daigram Star and Delta connections?

Google star delta motor connections. If a motor is wired in star-delta (Yd), it starts up with lots of torque and then switches over to delta for normal "running". This is because the start-up current per phase when delta connected is much larger than star.

Why star connected motor have high current compare to delta?

Gently we are using star delta starter for hiegh rating motors,,in star connection the line current is equal to the phase current and incase delta connection the line and phase voltages are equal,,at starting the current will be maximum.

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.

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

What is cable size for a 75 KW 3 phase induction motor 50 meter run for cable 415V?

For an Induction motor, it is recommended that the cable size should be able to bear high motor starting current. For a 75KW, the motor should be run with a special control method: an auto transformer method or Star/Delta method so as to reduce the earlier mentioned high starting current. Working with a star/delta control method, the motor starts in Star and Runs in Delta. Star arrangement delivers about 58% of the motor voltage and allows line current to pass into the coils of the motor so that you will require 2x50mm square copper cables per phase to power a 75KW induction motor.

How can you include phase failure relay in your star delta motor starter circuit?

The star delta motor starter circuit has to have a control voltage to energize the motor magnetic contractors. A phase failure relay monitors all three phases of the incoming supply lines. The phase failure relay also has auxiliary contacts on it. There are usually two sets of "C" form contacts. The control voltage for the starter circuit must be connected across the normally open (N.O.) contacts of one of these two sets. When the phase monitor is energized these N.O. contacts close supplying the control voltage to the circuitry of the star delta starters. If there is a phase interruption, phase reversal or phase loss, the phase failure relay will de-energize and the N.O. contacts will go back to their de-energized state. If the star delta motor starter is in use at the time, its control circuitry voltage will be lost and the delta motor magnetic contactor will open. The opening of this contactor will disconnect the motor from the failed three phase supply.

How many terminals are provided on the terminal box of a three phase squirrel cage induction motor to be started by a star delta starter?

The motor terminal box should have six wires coming out of it.

How does a star winding shifts to a delta winding in a three phase motor?

u can change in the terminal box..

What is the star delta working principle?

when starting a 3 phase induction motor,first start with star connection,because reduced current is being applied and after start change it to delta connection then. full line current is applied to the motor.

Are contactor points and bimetallic strip connected to the star delta starter of 3 phase induction motor?


The block diagram of a star delta starter?

input--> star configuration -->delta configuration. both configurtaion is connected to 3 phase motor coil. mail contactor is connected to both star and delta configuration. timer is connected to main contector....

How many windings in a 3 phase motor?

only three winding is there seperately ..we will decide to make a connection in outside ( motor terminals star or delta)

When you connect the motor do you use star or delta?

It depends on the motor. You need to look at the specifications of the particular motor. In general, if there are only three conductors, not counting earth, then it is delta; if there are four, then it is star; if there are six, then it is star-delta and you need a star-delta starter.

What should be the changeover time for 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.

How can the star and delta connections be combined to produce a star delta starter for an electric motor?

A star delta starter is one complete unit with all of the interlocks built in. The three phase supply is connected to the top terminals and the six wires from the motor connect to the appropriate terminals on the starter. All that has to be connected into the circuit is the timer that tells the starter when to drop the star starter coil and energize the delta starter coil to change from the start star connection to the run delta connection.

What is the connection of normal wire star or delta?

normally delta connection wired in 3 phase induction motor. during starting wiring is in Star and after running normal speed changeover to delta .beacause starting time its phase voltage equals less root3 times of line voltage ,line current and phase current equals. in Delta phase voltage and line voltage equals, and phase current equals root3 times line current

Can you convert transformed 3 phase 200 volt to single phase 200 volt?

In a three phase that means there are three lines live. Lets name the first line L1, second one L2 and the last L3. If you would connet it to a three phase motor then you require L1, L2 and L3 to be connected either in star or delta connection. Rating of your motor should be 200V, 3 phase , x HP ( star or delta connected). If you have a single motor of 200V then you only need to connect two lines of the three., namely either L1 to L2 , L1 to L3 or L2 to L3.

What is the no load current of a 2.2kW 3 phase 415V AC Motor?

1.6A for star connection and 1.95A for delta connection.