23-06-2015, 11:43 AM
circuit diagram of 3 phase automatic phase sequence corrector
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automatic phase changer circuit
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circuit diagram of 3 phase automatic phase sequence corrector
23-06-2015, 03:07 PM
automatic phase changer circuit
INTRODUCTION
Our project ‘Automatic Phase Changer’ is a simple circuit. It is applicable in three phase circuits. If anyone wants their equipment works at rated voltage, this circuit will help him. The circuit provides correct voltage in the same power supply lines through relays from the other phase where correct voltage is available. Using it you can operate all your equipment even when correct voltage is available on a single phase in the building.
1.1. Objective:
In three-phase applications, if low voltage is available in any one or two phases, and you want your equipment to work on normal voltage, this circuit will solve your problem. However, a proper-rating fuse needs to be used in the input lines (R, Y and B) of each phase. The circuit provides correct voltage in the same power supply lines through relays from the other phase where correct voltage is available. Using it you can operate all your equipment even when correct voltage is available on a single phase in the building.
The circuit is built around a transformer, comparator, transistor and relay. Three identical sets of this circuit, one each for three phases, are used.
1.2. Components required:
The circuit consist the following - transformer, comparator, transistor and relay. Three identical sets of this circuit are used, one each for three phases. Here the IC 741 working as the comparator is used here is surrounded by all other components. Here we use transformer, a step down transformer. Transistor BC557 acting as a switch. Relay is electromagnetic type.
Transformer - 12 V, 300mA
Transistor – BC557 (PNP)
Diode - IN4007
Zener Diode - 5.1 V
Capacitor - 1000microF, - 470microF, 35 V
Resistor - R1 & R2 – 3.3k - R3 – 10k
Potentiometer - 10k
LITERATURE SURVEY
The aim behind the mini project is to improve the professional competency by selecting those areas which otherwise are not covered in the normal course. This is to enhance our knowledge into various fields, and thus to gain work experience, confidence, and logical thinking. Our aim was to select a topic which is simple enough to be done within the specified time. So we are planned to do a simple project using basic electrical and electronic concept that we have studied yet. We interested to apply and modify the basic concept than a new topic to be selected. While selecting a topic for our mini project, the first thing which came to our mind was that it should be a product that has got considerable importance in the modern era.
2.1. Selection:
Our concentration was to develop a system which can reduce the problems or difficulties in our life. Also one more thing was in mind that to develop a system which can be applied for several applications associated with modern science and developments in technology. So the concept of automatic phase changer was selected which can be used in 3-phase applications. In 3 phase applications, if low voltage is available in any one of two phases and want equipment to work in normal voltage this circuit will solve your problem. It is a simple circuit. The circuit consists a comporator,transistor,transformer and relays. We use 741 Op-Amp in ‘comporator’ mode. This allows it to compare two input voltages.
2.2 Design of the circuit:
The circuit is built around a transformer, comparator, transistor and relay. Three identical sets of this circuit, one each for three phases, are used. Here we used a step down transformer. Here the IC 741 working as the comparator is used here is surrounded by all other components. Transistor BC557 acting as a switch. Relay is electromagnetic type. In automatic phase changer the main processes can be divided into four.
Step down the main supply
Rectification
Comparing
Switching
Main supply R, Y, B is stepped down to desired voltage and current. Each transformer is individually connected to the phases R, Y, B respectively. In this case, only one phase work at a time. The diodes (IN4007) are used to rectify the ac to dc. The capacitors for removing the noises in the dc. The resistors and potentiometers of the circuit is gives the specified voltage input to the comparator. Based on the comparator output, the transistor (BC557) goes to on and off positions. Thus we can say that transistor work as a switch.
Transformer - 12 V, 300mA; Transistor – BC557 (PNP); Diode - IN4007; Zener Diode 5.1 V; Capacitor - 1000microF, 12 V; 470microF, 35 V; Resistor - R1 & R2 – 3.3k, R3 – 10k; Potentiometer - 10k.
2.3. Assembling the Project:
Main components needed for the project are resistors, capacitors, diodes, transformer, comparator and relays. The components were mounted on the bread board and were wired up. A 12V dc supply was generated. The main circuit consist comparator, transformer, transistor and relay. Three identical sets of this circuit connected on the breadboard. Each one corresponds three phases. Then the output is verified by connecting a load (bulb) at the output and got the desired output.
In three-phase applications, if low voltage is available in any one or two phases, and you want your equipment to work on normal voltage, this circuit will solve your problem. However, a proper-rating fuse needs to be used in the input lines (R, Y and B) of each phase. The circuit provides correct voltage in the same power supply lines through relays from the other phase where correct voltage is available. Using it you can operate all your equipment even when correct voltage is available on a single phase in the building.
The circuit is built around a transformer, comparator, transistor and relay. Three identical sets of this circuit, one each for three phases, are used. Let us now consider the working of the circuit connecting red cable (call it ‘R’ phase).
The mains power supply phase R is stepped down by transformer X1 to deliver 12V, 300 mA, which is rectified by diode D1 and filtered by capacitor C1 to produce the operating voltage for the operational amplifier (IC1). The voltage at inverting pin 2 of oprational amplifier IC1 is taken from the voltage divider circuit of resistor R1 and preset resistor VR1. VR1 is used to set the reference voltage according to the requirement. The reference voltage at non-inverting pin 3 is fixed to 5.1V through zener diode ZD1.
Till the supply voltage available in phase R is in the range of 200V-230V, the voltage at inverting pin 2 of IC1 remains high, i.e., more than reference voltage of 5.1V, and its output pin 6 also remains high. As a result, transistor T1 does not conduct, relay RL1 remains de-energised and phase ‘R’ supplies power to load L1 via normally closed(N/C) contact of relay RL1.As soon as phase-R voltage goes below 200V, the voltage at inverting pin 2 of IC1 goes below reference voltage of 5.1V, and its output goes low.As a result, transistor T1 conducts and relay RL1 energises and load L1 is disconnected from phase ‘R’ and connected to phase ‘Y’ through relay RL2.Similarly, the auto phase-change of the remaining two phases, viz, phase‘Y’ and phase ‘B,’ can be explained.Switch S1 is mains power ‘on’/’off’ switch.
Use relay contacts of proper rating and fuses should be able to take-on the load when transferred from other phases. While wiring, assembly and installation of the circuit, make sure that you:
1. Use good-quality, multi-strand insulated copper wire suitable for your current requirement.
2. Use good-quality relays with proper contact and current rating.
3. Mount the transformer(s) and relays on a suitable cabinet. Use a Tag Block(TB) for incoming/out going connections from mains.
EFY Note: 1. During testing in the lab, we used a 12V, 200-ohm, single phase change over relay with 6A currentrating. Similarly, ampere-rated fuses were used.
2. If the input voltage is low in two phases, loads L1 and L2 may also be connected to the third phase. In that situation, a high-rating fuse will be required at the input of the third phase which is taking the total load.
INTRODUCTION
Our project ‘Automatic Phase Changer’ is a simple circuit. It is applicable in three phase circuits. If anyone wants their equipment works at rated voltage, this circuit will help him. The circuit provides correct voltage in the same power supply lines through relays from the other phase where correct voltage is available. Using it you can operate all your equipment even when correct voltage is available on a single phase in the building.
1.1. Objective:
In three-phase applications, if low voltage is available in any one or two phases, and you want your equipment to work on normal voltage, this circuit will solve your problem. However, a proper-rating fuse needs to be used in the input lines (R, Y and B) of each phase. The circuit provides correct voltage in the same power supply lines through relays from the other phase where correct voltage is available. Using it you can operate all your equipment even when correct voltage is available on a single phase in the building.
The circuit is built around a transformer, comparator, transistor and relay. Three identical sets of this circuit, one each for three phases, are used.
1.2. Components required:
The circuit consist the following - transformer, comparator, transistor and relay. Three identical sets of this circuit are used, one each for three phases. Here the IC 741 working as the comparator is used here is surrounded by all other components. Here we use transformer, a step down transformer. Transistor BC557 acting as a switch. Relay is electromagnetic type.
Transformer - 12 V, 300mA
Transistor – BC557 (PNP)
Diode - IN4007
Zener Diode - 5.1 V
Capacitor - 1000microF, - 470microF, 35 V
Resistor - R1 & R2 – 3.3k - R3 – 10k
Potentiometer - 10k
LITERATURE SURVEY
The aim behind the mini project is to improve the professional competency by selecting those areas which otherwise are not covered in the normal course. This is to enhance our knowledge into various fields, and thus to gain work experience, confidence, and logical thinking. Our aim was to select a topic which is simple enough to be done within the specified time. So we are planned to do a simple project using basic electrical and electronic concept that we have studied yet. We interested to apply and modify the basic concept than a new topic to be selected. While selecting a topic for our mini project, the first thing which came to our mind was that it should be a product that has got considerable importance in the modern era.
2.1. Selection:
Our concentration was to develop a system which can reduce the problems or difficulties in our life. Also one more thing was in mind that to develop a system which can be applied for several applications associated with modern science and developments in technology. So the concept of automatic phase changer was selected which can be used in 3-phase applications. In 3 phase applications, if low voltage is available in any one of two phases and want equipment to work in normal voltage this circuit will solve your problem. It is a simple circuit. The circuit consists a comporator,transistor,transformer and relays. We use 741 Op-Amp in ‘comporator’ mode. This allows it to compare two input voltages.
2.2 Design of the circuit:
The circuit is built around a transformer, comparator, transistor and relay. Three identical sets of this circuit, one each for three phases, are used. Here we used a step down transformer. Here the IC 741 working as the comparator is used here is surrounded by all other components. Transistor BC557 acting as a switch. Relay is electromagnetic type. In automatic phase changer the main processes can be divided into four.
Step down the main supply
Rectification
Comparing
Switching
Main supply R, Y, B is stepped down to desired voltage and current. Each transformer is individually connected to the phases R, Y, B respectively. In this case, only one phase work at a time. The diodes (IN4007) are used to rectify the ac to dc. The capacitors for removing the noises in the dc. The resistors and potentiometers of the circuit is gives the specified voltage input to the comparator. Based on the comparator output, the transistor (BC557) goes to on and off positions. Thus we can say that transistor work as a switch.
Transformer - 12 V, 300mA; Transistor – BC557 (PNP); Diode - IN4007; Zener Diode 5.1 V; Capacitor - 1000microF, 12 V; 470microF, 35 V; Resistor - R1 & R2 – 3.3k, R3 – 10k; Potentiometer - 10k.
2.3. Assembling the Project:
Main components needed for the project are resistors, capacitors, diodes, transformer, comparator and relays. The components were mounted on the bread board and were wired up. A 12V dc supply was generated. The main circuit consist comparator, transformer, transistor and relay. Three identical sets of this circuit connected on the breadboard. Each one corresponds three phases. Then the output is verified by connecting a load (bulb) at the output and got the desired output.
In three-phase applications, if low voltage is available in any one or two phases, and you want your equipment to work on normal voltage, this circuit will solve your problem. However, a proper-rating fuse needs to be used in the input lines (R, Y and B) of each phase. The circuit provides correct voltage in the same power supply lines through relays from the other phase where correct voltage is available. Using it you can operate all your equipment even when correct voltage is available on a single phase in the building.
The circuit is built around a transformer, comparator, transistor and relay. Three identical sets of this circuit, one each for three phases, are used. Let us now consider the working of the circuit connecting red cable (call it ‘R’ phase).
The mains power supply phase R is stepped down by transformer X1 to deliver 12V, 300 mA, which is rectified by diode D1 and filtered by capacitor C1 to produce the operating voltage for the operational amplifier (IC1). The voltage at inverting pin 2 of oprational amplifier IC1 is taken from the voltage divider circuit of resistor R1 and preset resistor VR1. VR1 is used to set the reference voltage according to the requirement. The reference voltage at non-inverting pin 3 is fixed to 5.1V through zener diode ZD1.
Till the supply voltage available in phase R is in the range of 200V-230V, the voltage at inverting pin 2 of IC1 remains high, i.e., more than reference voltage of 5.1V, and its output pin 6 also remains high. As a result, transistor T1 does not conduct, relay RL1 remains de-energised and phase ‘R’ supplies power to load L1 via normally closed(N/C) contact of relay RL1.As soon as phase-R voltage goes below 200V, the voltage at inverting pin 2 of IC1 goes below reference voltage of 5.1V, and its output goes low.As a result, transistor T1 conducts and relay RL1 energises and load L1 is disconnected from phase ‘R’ and connected to phase ‘Y’ through relay RL2.Similarly, the auto phase-change of the remaining two phases, viz, phase‘Y’ and phase ‘B,’ can be explained.Switch S1 is mains power ‘on’/’off’ switch.
Use relay contacts of proper rating and fuses should be able to take-on the load when transferred from other phases. While wiring, assembly and installation of the circuit, make sure that you:
1. Use good-quality, multi-strand insulated copper wire suitable for your current requirement.
2. Use good-quality relays with proper contact and current rating.
3. Mount the transformer(s) and relays on a suitable cabinet. Use a Tag Block(TB) for incoming/out going connections from mains.
EFY Note: 1. During testing in the lab, we used a 12V, 200-ohm, single phase change over relay with 6A currentrating. Similarly, ampere-rated fuses were used.
2. If the input voltage is low in two phases, loads L1 and L2 may also be connected to the third phase. In that situation, a high-rating fuse will be required at the input of the third phase which is taking the total load.
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