Three Phase Solid State Relay with ZVS using pic microcontroller

Three Phase Solid State Relay with ZVS:A relay is an electrically controllable switch, which is mostly used in industrial and home appliances applications. Two types of relays are widely used, one is electromechanically relay which have an electromagnetic coil, spring and electromechanical moving contacts. This relay is operated at high voltage and high current and arc is produced when it is operated. One is an electronic relay which is also called solid state relay. This relay has no electromagnetic coil, no electromechanical moving contact and no spring. This relay is only made up with the help of semiconductor material and can easily operate at low voltage and low current. It is operated at zero voltage switching, means, when it is operated at ac loads then this relay is turns on at zero voltage because the ac voltage has negative and positive cycle but also has the time when this cycle is at zero volt. When the relay is operated at this voltage then there is no any arc produced. Here we would be made a three-phase solid state relay with the help of pic microcontroller 18F452, triac and optocoupler for operating the three-single phase load.

The Block Diagram of Three Phase Solid State Relay with ZVS

Figure 1 The Block diagram of Three Phase Solid State relay with ZVSThree Phase Solid State Relay with Zero Voltage Switching

Components List and Detail of Three Phase Solid State Relay with ZVS

Transformer:Transformer is a ac voltage device which is used for step up or step down the ac voltage and it is also used for isolation purposes. Here we would be use this for step down the 220 v ac into 12 v ac. It consists of two winding primaries and secondary and operate at the principle of mutual induction.

Bridge Rectifier:In this three-phase solid state relay system the voltage which is gained from transformer is ac voltage. These voltages are converted into dc through the bridge rectifier. It consists of four diodes andis connected at the output side of transformer.

Voltage Regulator:In this three-phase solid state relay system the 12 v dc voltages are regulated into 5 v dc with the help of voltage regulator. Which is connected at the output of bridge rectifier. The LM7805 voltage regulator is used here.

Microcontroller PIC 18F452: In this three-phase solid state relay system the pic microcontroller is used for the intelligent switching of connected three single phase loads. It is powered up with the help of voltage regulator and is interfaced with optocouplers. It is programmed in c language by using the mikro/c software. It is 40 pins microcontroller and these pins can configure as input or output.




Optocoupler: In this three-phase solid state relay system the optocoupler is used for operating the triac. It is 6 pins integrated circuit IC and is interfaced with microcontroller for switching the output loads at the zero-voltage. It also provides the electrical isolation between the input circuit and output load.

Triac:Triac is a semiconductor switch, which consists of a three-terminals anode 1, anode 2 and gate. It conducts in both directions when it is triggered by giving the gate pulse at gate terminal. This gate pulse is generated by the microcontroller after sensing the ac voltage.

Output Load: In this three-phase solid state relay system the three lamps are used as an output load, which are operated at 230 v ac and directly connected to wapda power supply. Here we can also connect the inductive load such as motor or any other.

Working Principle of Three Phase Solid State Relay with ZVS

The working principle of this three-phase solid state relay system is that, this system works on the principle of zero voltage switching. The ac voltages, which have the frequency 50 Hz normally. Each cycle of the ac voltages has three state, positive, zero and negative. All these states, sensed by the microcontroller with the help of optocoupler. When the ac voltages are at zero state then the microcontroller switch on the ac load by giving the switching pulse at the gate of triac.In this system the output load is directly connected to the wapda power supply. This system has three switches one is used for power on this system and remaining two switches are used for operating this system at low frequency and high frequency. The output lamps are only used for checking this system either it would be turn on or off at high and low frequency switching. Firstly, this system is checked at low switching frequency by pressing the low frequency switch. At this frequency, the lamps make on/off randomly with low brightness and on or off time can be checked by using the oscilloscope. This oscilloscope tells us either the lamps make on/off at zero voltage switching. Secondly this system is checked at high frequency by pressing the high frequency switch. At this frequency, the lamps glow randomly but with full brightness. So, the option is available in this system can be used at low and high switching frequency.

 Applications and Advantages of Three Phase Solid State Relay with ZVS

  1. The three-phase solid state relay can be used in industrial applications instead of ac circuit breaker or relays   such as for driving the three phase ac motors.
  2. The three-phase solid state relay has same working behavior for inductive and resistive loads.
  3. This three- phase solid state relay can be used in electronics switch loads which are used for testing the dc converters.
  4. This solid-state relay can be used in cooking equipment, medical equipment, plastic machinery, packing machinery, lighting system and laboratory ovens.
  5. This three-phase solid state relay because it is operated at zero voltage switching therefore there is on any voltage or current spikes or arc is produced.
  6. This relay is more reliable and efficient as compared to the other electrical relays.
  7. This relay has low production cost as compared the others relays.
  8. This relay can easily operate at low voltage and low current.

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