NECESSITY OF STARTER
For starting 3 Phase Induction Motor if rated voltage is given to the starter of motor very high. Starting current will flow through the motor winding. (I.e. 5 to 6 times the Running Current). This Starting or initial high current is objectionable, because it will produce large line voltages drop, Which n turn will effect the operation of other electrical Equipment and line connection to the same line.
The Starting current is controlled by apply a reduced voltage to the Stator winding during the Starting time, and then full normal voltage is applied. When the motor has run up to speed.
NOTE:-
For Small capacity motor, say up to 3HP. Full normal voltage can be applied to the start.
ADVANTAGES OF STARTER
1} To Start and stop the motor.
2} protect the motor from overload current & low voltage.
3} protect the motor from Single phasing.
4} The Starter may also reduced the applied voltage to the motor at the time of Starting.
Starter operated either Mechanical or Electrical System. It for switching on a mechanical system is used in the Starter, Then it is known as manually operated starter, If an Electromagnetic contactor is utilized, Then it is Called Electrically operated Starter. All Starters above 2HP are Usually Electrically operated. In Addition to Starter are provided with safety devices like over load relay, and no. Volt coil for protection of the motor.
TYPES OF STARTER
1} Direct on line (D.O.L.) Starter- (Mechanically Operated)
2} Direct on line (D.O.L.) Starter-(Electrically Operated)
3} Star Delta Starter (Manually Operated)
4} Star Delta Starter (Semi Automatic)
5} Star Delta Starter (Fully Automatic)
6} Slipring Motor Starter
7} Auto Transformer Starter
In the above Starter Except for the Direct in line Starter reduced voltage is applied to the stator of the motor. at the time of Starting, and normal voltage is applied once the motor pick up the Speed.
PARTS OF STARTER
1} Contactor
a) Main Contactor b) Auxiliary Contactor
2} N.V.C.
3} O.L.R.C.
SELECTION OF STARTER
Factor must be considered when selecting starting equipment for motor. I.e. starter
1} Starting Current
2} Full Load Current
3} Voltage Rating of Motor
4} Voltage Drop
5} Cycle of Operation
6} Type of Load
7} Motor protection and Safety of the operator.
PART OF STARTER
CONTACTOR:-
Contactor forms the main part in all the Starter. A Contactor may be defined like this Capable of making or Breaking the load circuit. At Frequency of 60 c/h or more. It may be operated by hand or (Mechanical). Electromagnetic, Prelatic or Electro Primate Relays.
MAIN CONTACTOR: -
There are Three sets of normally open, Main contact between Terminals. 1& 2, 3 and 4, 5&6 two sets of normally open.
AUXILARY CONTACT: -
Auxiliary Contact between terminals 2,3&24, 13&14. One set of normally closed contact between the terminals 21&22. Auxiliary Contact carries current than the main Contact.
N.V.C.(No Volt Coil):-
No Volt Coil means Electromagnetic it works on 440V. Due to this Magnetic action moving contacts to the fixed contact. Then motor run at its normal Speed.
Here N.V.C. ON push button. OFF push button and OLRC are series with the Circuit.
The Voltage between any two phases 440V. I.e. L1&L2/R&Y. This Control circuit N.V.C. becomes Magnetic. It contacts the movable contact to the fixed Contact.
O.L.R.C. (Over Load Relay Coil):- The over load relay protect the motor against high current. Normal over load existing for long times Single phasing effects.
These Relays have Characteristics. Which help the relay to open the Contractor in 10 seconds.
TYPES OF RELAYS
1} Bimetallic Over Load Relays
2} Magnetic Over Load Relays
RELAYS SETTING:-
The load relay unit is the protection center if the motor starter. Relays come in number of Ranges. Selection of a relay for a starter depends upon the Motor types, rating & Duty cycles.
For all D.O.L. Starter, relays should be set to the actual current of the motor. This value should be equal to or Lower than the full load current. Indicated on the name plate of the motor.
Set the relay to about 80% of the full load current. If it trip increase the setting to 85% or more till the Relay Holts.
In Control circuit when ON push button is pressed, the control circuit closed. The N.V.C. Coil is magnetized, and the Contactor closes. An Auxiliary a normally open contact is also actuated together with the main contact. If normally open Contact is connected in Parallel with the ON Switch. It is called a self holding Auxiliary Contact.
When for starting the motor by pressing the ON push button. Current flowing through ON Switch. N.V.C. becomes magnet due to connect 440V A.C. When ON push button released the current flowing via auxiliary contact till contactors release.
STAR.DELTA.STARTER
Necessity of Star Delta Star-Delta Starter for 3 Phase Squirrel Cage Induction Motor.
If a3 phase Squirrel cage induction motor is started directly, it takes about 6-7 times. The full load current for few seconds, and then current reduces to normal value once the speed accelerates to its rated value.
However large capacity motors, the starting current will cense too much. Voltage Fluctuations in the power lines and disturb. the other loads On the other hands, if all the Squirrel cage motors Connected to the power lines are started at the same time, They Momentarily over load the power lines, Transformers and even the alternators.
Because of these reasons, the applied voltage to the Squirrel cage motor needs to be reduced during the starting periods and regular supply could be given when the motor pick up its speed.
Following Methods of reducing the applied voltage to the Squirrel cage motor at the Start.
1} a) Star Delta Starter- (Manually Operated)
b) Star Delta Starter- (Fully Automatic)
c) Star Delta Starter- (Semi Automatic)
2} Auto Transformer Starter
3} Step Down Transformer Starter
Star-Delta Starter:- In star delta starter over load relay and under voltage protection through circuit fuses. In a Star Delta Starter, at the time of starting. The Squirrel cage motor is connected in star so that. The phase voltage us reduced to 1/1.73times. The line voltage and when motor pick up its Speed, The Windings are connected in delta. To connect delta starter to a 3 phase squirrel cage motor, all six terminals of the motor winding must be available.
MANUALLY OPERATED STAR DELTA STARTER
As the insulated handle is spring loaded, it will come back to OFF position from any position unless and until the no volt coil is Energized. When the hold on coil circuit is closed though the supply taken from U2&W2. The coil is Energized and it holds the plunger, and their by the handle is held in delta position against the spring tension by the lever plate mechanism. When the no. Volt coil is De-Energized/De-Magnetized. The Plunger falls and operates the lever plate mechanism so as to make the handle to be through to the OFF position due to spring tension. Which make it impossible for the operator to put the handle is brought to star position first, and then when the motor pick up speed, the handle is pushed to OFF position.
The Handle has a set of Baffle insulated from each other and also from the handle, When the handle is thrown to Star position, The baffles connect the supply lines. L1,L2&L3 to beginning of the 3 phase winding W1,V1&U2 respectively. At the same time the small baffles connect V2, W2&U2 Through the shorting cable to form the star point.
When the handle is thrown to delta position, The longer end of baffles connect the main supply line L1,L2&L3 to the winding terminals W1 U2,V1 W2,U1 V2 respectively to from the delta connection.
The overload relay current setting could be adjusted by the worm gear mechanism of the insulated rod. When the loads current exceed a stipulated value, the heat developed in the relay heater element. Pushes the rod to open the no. volt coil circuit, and the coil is De-magnetized, and the handle return to the OFF position Due to the spring tension.
The motor also could be stopped by operating the stop button.
For starting 3 Phase Induction Motor if rated voltage is given to the starter of motor very high. Starting current will flow through the motor winding. (I.e. 5 to 6 times the Running Current). This Starting or initial high current is objectionable, because it will produce large line voltages drop, Which n turn will effect the operation of other electrical Equipment and line connection to the same line.
The Starting current is controlled by apply a reduced voltage to the Stator winding during the Starting time, and then full normal voltage is applied. When the motor has run up to speed.
NOTE:-
For Small capacity motor, say up to 3HP. Full normal voltage can be applied to the start.
ADVANTAGES OF STARTER
1} To Start and stop the motor.
2} protect the motor from overload current & low voltage.
3} protect the motor from Single phasing.
4} The Starter may also reduced the applied voltage to the motor at the time of Starting.
Starter operated either Mechanical or Electrical System. It for switching on a mechanical system is used in the Starter, Then it is known as manually operated starter, If an Electromagnetic contactor is utilized, Then it is Called Electrically operated Starter. All Starters above 2HP are Usually Electrically operated. In Addition to Starter are provided with safety devices like over load relay, and no. Volt coil for protection of the motor.
TYPES OF STARTER
1} Direct on line (D.O.L.) Starter- (Mechanically Operated)
2} Direct on line (D.O.L.) Starter-(Electrically Operated)
3} Star Delta Starter (Manually Operated)
4} Star Delta Starter (Semi Automatic)
5} Star Delta Starter (Fully Automatic)
6} Slipring Motor Starter
7} Auto Transformer Starter
In the above Starter Except for the Direct in line Starter reduced voltage is applied to the stator of the motor. at the time of Starting, and normal voltage is applied once the motor pick up the Speed.
PARTS OF STARTER
1} Contactor
a) Main Contactor b) Auxiliary Contactor
2} N.V.C.
3} O.L.R.C.
SELECTION OF STARTER
Factor must be considered when selecting starting equipment for motor. I.e. starter
1} Starting Current
2} Full Load Current
3} Voltage Rating of Motor
4} Voltage Drop
5} Cycle of Operation
6} Type of Load
7} Motor protection and Safety of the operator.
PART OF STARTER
CONTACTOR:-
Contactor forms the main part in all the Starter. A Contactor may be defined like this Capable of making or Breaking the load circuit. At Frequency of 60 c/h or more. It may be operated by hand or (Mechanical). Electromagnetic, Prelatic or Electro Primate Relays.
MAIN CONTACTOR: -
There are Three sets of normally open, Main contact between Terminals. 1& 2, 3 and 4, 5&6 two sets of normally open.
AUXILARY CONTACT: -
Auxiliary Contact between terminals 2,3&24, 13&14. One set of normally closed contact between the terminals 21&22. Auxiliary Contact carries current than the main Contact.
N.V.C.(No Volt Coil):-
No Volt Coil means Electromagnetic it works on 440V. Due to this Magnetic action moving contacts to the fixed contact. Then motor run at its normal Speed.
Here N.V.C. ON push button. OFF push button and OLRC are series with the Circuit.
The Voltage between any two phases 440V. I.e. L1&L2/R&Y. This Control circuit N.V.C. becomes Magnetic. It contacts the movable contact to the fixed Contact.
O.L.R.C. (Over Load Relay Coil):- The over load relay protect the motor against high current. Normal over load existing for long times Single phasing effects.
These Relays have Characteristics. Which help the relay to open the Contractor in 10 seconds.
TYPES OF RELAYS
1} Bimetallic Over Load Relays
2} Magnetic Over Load Relays
RELAYS SETTING:-
The load relay unit is the protection center if the motor starter. Relays come in number of Ranges. Selection of a relay for a starter depends upon the Motor types, rating & Duty cycles.
For all D.O.L. Starter, relays should be set to the actual current of the motor. This value should be equal to or Lower than the full load current. Indicated on the name plate of the motor.
Set the relay to about 80% of the full load current. If it trip increase the setting to 85% or more till the Relay Holts.
In Control circuit when ON push button is pressed, the control circuit closed. The N.V.C. Coil is magnetized, and the Contactor closes. An Auxiliary a normally open contact is also actuated together with the main contact. If normally open Contact is connected in Parallel with the ON Switch. It is called a self holding Auxiliary Contact.
When for starting the motor by pressing the ON push button. Current flowing through ON Switch. N.V.C. becomes magnet due to connect 440V A.C. When ON push button released the current flowing via auxiliary contact till contactors release.
STAR.DELTA.STARTER
Necessity of Star Delta Star-Delta Starter for 3 Phase Squirrel Cage Induction Motor.
If a3 phase Squirrel cage induction motor is started directly, it takes about 6-7 times. The full load current for few seconds, and then current reduces to normal value once the speed accelerates to its rated value.
However large capacity motors, the starting current will cense too much. Voltage Fluctuations in the power lines and disturb. the other loads On the other hands, if all the Squirrel cage motors Connected to the power lines are started at the same time, They Momentarily over load the power lines, Transformers and even the alternators.
Because of these reasons, the applied voltage to the Squirrel cage motor needs to be reduced during the starting periods and regular supply could be given when the motor pick up its speed.
Following Methods of reducing the applied voltage to the Squirrel cage motor at the Start.
1} a) Star Delta Starter- (Manually Operated)
b) Star Delta Starter- (Fully Automatic)
c) Star Delta Starter- (Semi Automatic)
2} Auto Transformer Starter
3} Step Down Transformer Starter
Star-Delta Starter:- In star delta starter over load relay and under voltage protection through circuit fuses. In a Star Delta Starter, at the time of starting. The Squirrel cage motor is connected in star so that. The phase voltage us reduced to 1/1.73times. The line voltage and when motor pick up its Speed, The Windings are connected in delta. To connect delta starter to a 3 phase squirrel cage motor, all six terminals of the motor winding must be available.
MANUALLY OPERATED STAR DELTA STARTER
As the insulated handle is spring loaded, it will come back to OFF position from any position unless and until the no volt coil is Energized. When the hold on coil circuit is closed though the supply taken from U2&W2. The coil is Energized and it holds the plunger, and their by the handle is held in delta position against the spring tension by the lever plate mechanism. When the no. Volt coil is De-Energized/De-Magnetized. The Plunger falls and operates the lever plate mechanism so as to make the handle to be through to the OFF position due to spring tension. Which make it impossible for the operator to put the handle is brought to star position first, and then when the motor pick up speed, the handle is pushed to OFF position.
The Handle has a set of Baffle insulated from each other and also from the handle, When the handle is thrown to Star position, The baffles connect the supply lines. L1,L2&L3 to beginning of the 3 phase winding W1,V1&U2 respectively. At the same time the small baffles connect V2, W2&U2 Through the shorting cable to form the star point.
When the handle is thrown to delta position, The longer end of baffles connect the main supply line L1,L2&L3 to the winding terminals W1 U2,V1 W2,U1 V2 respectively to from the delta connection.
The overload relay current setting could be adjusted by the worm gear mechanism of the insulated rod. When the loads current exceed a stipulated value, the heat developed in the relay heater element. Pushes the rod to open the no. volt coil circuit, and the coil is De-magnetized, and the handle return to the OFF position Due to the spring tension.
The motor also could be stopped by operating the stop button.
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