DESCRIPTION FIELD OF INVENTION

The present invention relates to the field of Power Electronics and finds its use in the Control of Alternate Current inputs. In particular, the present invention relates to the controlling of a circuit by means of a lower power signal. More particularly, the present invention involves in the handling of 25 Amps of AC current per channel at a maximum blocking voltage of 800Volt ac per channel. Furthermore the present invention involves the handling of totally 100Amps with 800Volts blocking voltage for all channels.

BACKGROUND OF INVENTION

In the technology involved in controlling of AC current inputs, relays are used where it is necessary to control a circuit by a low-power signal (with complete electrical isolation between control and controlled circuits).

There are various types of relays. One type of relay used to perform the operation of handling of high power which is required to control an electric motor or other loads is called as a 'contactor'. The other type is known as 'Solid State Relay' which is used to control power circuits without any moving parts and instead uses a Semiconductor device for performing the action of Switching.

But, it can be observed that a critical and important requirement of Solid State Relays is that the total current and the voltage insulation between various channels is to be maintained in such a way that the electronic operation of any given particular channel should not be affecting the operation of the other channel. This is very important for the operational efficiency of any Solid state relay system / device.

OBJECT OF THE INVENTION

It is an object of the invention to provide a Solid state relay system / device for the controlling of Alternate Currents.

It is a further object of the invention to provide a Solid state Relay system, which can handle 25 Amps of Alternating current per channel at a maximum blocking voltage of 800Volt ac per channel and the whole relay can handle totally 100Amps with 800Volts blocking voltage for all channels.

Yet another object of the invention is to provide a Solid State Relay system, wherein, without its control voltage (i.e. input control voltage being zero), the channels are capable of conducting current fully with less than 2 volts of voltage drop across each channel.

A further object of the present invention, is to provide a Solid State Relay system which is capable of controlling voltage of Alternate Currents and all the features along with the electronic and electrical operations are accommodated inside a relatively small package, with output terminals for conduction and looping it to another relay for parallel or serial operation.

DETAILED DESCRIPTION OF THE INVENTION

In the Solid State Relay System / device, the control voltage from 5 to 30volts, of either Direct or Alternating Current is provided to pins TP1 or TP2 and TP3 or TP4. Diode D1 acts as a rectifier diode and also as a polarity reverse protection diode. The control voltage in the form of AC is rectified by this diode and is filtered by the capacitor C2 to convert it to DC. This DC is then regulated using the Zener diodes Z1, Z2, Z3, Z4 via resistors"R.1, R5, R9, R13.

The 12 volts DC generated across the zener is then provided to the IRED (Infra Red Emitting Diode) of the optocoupler IC's U1, U2, U3, U4. The zener diode protects the optocoupler from any incoming high voltage and also maintains the voltage across the optocoupler IRED to 12 volts even when the control voltage goes above 12 volts. Whenever the input control voltage is less than 12volts then the same voltage is available across the optocoupler IRED. The range of control voltage designed for this circuit is from 5 to 30 volts AC or DC that enables the optocoupler transistor to go into conduction mode.

The optocoupler's optically isolated transistor collector is connected to the gate of the SCR (Silicon Control Rectifier) Q1. Correspondingly, the collectors of the remaining transistors of the optocoupler IC's are connected to the gates of Q2, Q3, Q4. The collectors of these transistors are also connected to the Anodes of the SCR's through resistors R2, R6, R10, R14, and the emitters of these transistors are connected to the Cathodes of all the respective SCR's.

The Anodes of the SCR's are connected to the positive output of the bridge rectifier BR1,BR2,BR3,BR4, respectively and the Cathodes are connected to the negative output of the bridge rectifiers respectively. The AC section of the bridge rectifier is connected to the Triacs T1, T2, T3, T4 through resistors R3, R7, R11, R16 to their gates. And the AC input and output is provided through pins TP5, TP6 and TP7, TP8 and TP9, TP10 and TP11, TP12 respectively.

Snubber circuit built around series combination of resistors and capacitors R4.C1, R6,C3, R12.C4, and R16, C5 protects respective Triacs from any high dV/dt change in voltage the values of Rand C selected are suitable for this circuit.

It can be observed that when AC mains is connected through TP5 and TP6 to a load in series the Triac goes in full conduction mode by self-biasing its gate through resistor R3 the bridge rectifier provides a ripple DC across the SCR Q1 and the SCR Q1 gets its bias through the R2 resistor. In this way the Triac and the SCR remains in the full conduction mode and powers any load that is connected through this Triac. Similar operation occurs with all the remaining Triacs when they are connected to

AC mains in series to a user load. Thus all the Triacs will be ON without any control voltage at the input side of this four pole relay.

When a DC or an AC voltage in the range of 5 to 30 volts is applied across the pins TP1 or TP2 and TP3 or TP4 the optocoupler IRED enables the optotransistor to go into full conduction mode and the transistors ground the gates of the SCR to go into disable mode. In this way the SCR's block the gate bias of the power Triacs and take them into full non conduction mode and the AC mains going to the user connected load is OFF. Similar operation occurs for all the remaining Triacs whenever a control voltage is provided at the input of this four pole relay.

All the components are at least 4 times de rated than its voltage break down value to maintain high reliability of this product to function under any industrial environmental condition. And the thermal energy generated by the four Triacs are directly provided to a relatively thick Aluminum heat sink to maintain continuous current conduction without thermal run away through all the Triacs. And the electronic and mechanical design is done in such a way that the operation of one optically isolated circuit does not effect the operation of the other and all the four Triacs can be controlled to go into ON or OFF mode synchronously by the applied control voltage.

CLAIMS

We claim:

A solid state Relay System / Device with common AC and DC control input that is capable of handling about 25 amps of AC current per channel at a blocking voltage of about 800 Volt AC per channel.

The invention as claimed in claim 1, wherein, the solid state Relay System / Device with common AC and DC control input that is capable of handling about 25Amps of AC current at a blocking voltage of about 800 Volt AC per channel.

The invention as claimed in claim 2, wherein, the channels are capable of conducting current fully with a voltage drops of less than 2 volts, even when the input control voltage is zero.

The invention as claimed in claim 2, wherein, the solid state relay system is capable of controlling voltage of Alternate currents with provisions for electrical and electronic operations accommodated inside a small package and with provisions of output terminals for conduction and looping it to another relay for parallel or serial operation.

The invention as claimed in claim 2, wherein, a) a control voltage of about 5 to 30 volts in the form of Direct or Alternating Current is provided to pins TP1 or TP2 and TP3 or TP4,

b) diode D1 acts as a rectifier diode and also as a polarity reverse protection diode, said control voltage in the form of AC is rectified by the Diode D1 and is filtered by the capacitor C2 to convert it to DC, said DC is then regulated using the Zener diodes Z1, Z2, Z3, Z4 via resistors R1, R5, R9, R13, wherein about 12 volts dc generated across the zener is then provided to the IRED of the optocoupler IC's U1, U2, U3, U4, said zener diode protects the optocoupler from any incoming high voltage and also maintains the voltage across the optocoupler IRED to about 12 volts even when the control voltage goes above 12 volts, said Zener diode maintains the voltage across the optocoupler IRED whenever the input control voltage is less than 12volts, said control voltage designed for the circuit from about 5 to 30 volts AC or DC that enables the optocoupler transistor to go into conduction mode, h) said optocoupler's optically isolated transistor collector connected to the gate of the SCR (Silicon Control Rectifier) Q1 and correspondingly the collectors of the remaining transistors of the optocoupler IC's are connected to the gates of Q2, Q3, Q4, i) said collectors of these transistors also connected to the Anodes of the SCR's through resistors R2, R6, R10, R14, and the emitters of these transistors connected to the Cathodes of all the respective SCR's, j) said Anodes of the SCR's connected to the positive output of the bridge rectifier BR1, BR2, BR3, BR4, and the Cathodes connected to the negative output of the bridge rectifiers respectively, k) AC section of the bridge rectifier connected to the Triacs T1, T2, T3, T4 through resistors R3, R7, R11, R16 to their gates and the AC input and output is provided through pins TP5, TP6 and TP7, TP8 and TP9, TP10 and TP11, TP12 respectively. I) a Snubber circuit is built around series combination of resistors and capacitors R4.C1, R6.C3, R12.C4, and R16, C5 to protect respective Triacs from any high dV/dt change in voltage wherein the values of Rand C selected are suitable for this circuit,

6. The invention as claimed in claim 5, wherein, when AC mains is connected through TP5 and TP6 to a load in series, the Triac goes in full conduction mode by self- biasing its gate through resistor R3 and the bridge rectifier provides a ripple DC across the SCR Q1 and the SCR Q1 gets its bias through the R2 resistor, thereby enabling the Triac and the SCR to remain in the full conduction mode and power any load that is connected through this Triac.

7. The invention as claimed in claim 6, wherein, similar operation occurs with all the remaining Triacs when they are connected to AC mains in series to a use; load and all the Triacs will be ON without any control voltage at the input side of the four pole relay.

The invention as claimed in claim 5, wherein, when a DC or an AC voltage in the range of 5 to 30 volts is applied across the pins TP1 or TP2 and TP3 or TP4, the optocoupler IRED enables the optotransistor to go into full conduction mode and the transistors ground the gates of the SCR to go into disable mode thereby blocking the gate bias of the power Triacs and take them into full non conduction mode resulting in the AC mains going to the user connected load to be OFF.

The invention as claimed in claim 8, wherein, similar operation occurs for all the remaining Triacs whenever a control voltage is provided at the input of this four pole relay.