MUHAMMAD ILYAS GHUMMANROLL No.12063122-088

SERIES OPERATION OF THYRISTORS.

AND

PARALLEL OPERATION OF THYRISTORS.

REVIEW SOME BASICSVacuum tubes

SOLID STATE PHYSICDIODES, BJTS ,FETS,THYRISTORS, ICS

UNDERSTAND JUNCTIONS OF THYRISTOR

VARIOUS TRIGGERING METHODS OF THYRISTOR

There are some methods for practically triggering of thyristors.

1 : Forward voltage triggering method.

2 : Thermal or temperature method.

3 : Radiation or light triggering method.

4 : dv\dt triggering method.

5 : Gate triggering method.

THYRISTOR EQUIVALENT CCT , WORKING AND 5 WAYS TO ON THE THYRISTORS.

INTRODUCTION OF (SCR) THYRISTOR ITS LATCHING AND CHECKING METHOD

INTRODUCTION OF (GTO) THYRISTORS , OPERATION AND CHECKING METHOD

WORKING OF THYRISTOR

THYRISTOR IN ON CONDITIONTHROUGH GATE

THYRISTOR IN OFF CONDITION

CONTROL OF THYRISTR BY +Ve AND –Ve PULSE

SERIES OPERATION OF THYRISTORS :

For high voltage application two or more then two thyristors can be connected in series to provide specific voltage rating .

How ever due to the production spread, characteristics of thyristors of the same type are not identical.

SERIES OPERATION OF THYRISTORS :

In the case of diodes , only the reverse blocking voltages have to be shared .

where as for thyristors , the voltage sharing networks are required for both reverse and off state condition .

The voltage sharing is normally accomplished by connecting resistors across each thyristor .

SERIES OPERATION OF THYRISTORS

For equal voltage sharing ,the off- state current differ . Let here be ns, thyristors in the string .

The off-state current of thyristor T1 is ID1 and that of other thyristors are equal such that ID2=ID3=IDn, andID1<ID2.

Because thyristor T1 has the least off state current,T1 shares higher voltage.

SERIES OPERATION OF THYRISTORS :

SERIES OPERATION OF THYRISTORS :

If I1 is the current through the resistor R acrossT1 and current through other resistors are equal so that I2=I3=In, the off-state current spread is shown on the next page.

SERIES OPERATION OF THYRISTORS :

SERIES POERATION OF THYRISTORS :

SERIES POERATION OF THYRISTORS :

PARALLEL OPERATION OF THYRISTOR

When thyristors are connected in parallel ,the load current is not shared equally due to differences in their characteristics .

If a thyristor carries more current than that of the others ,its power dissipation increases , their by increasing junction temperature.

Parallel operation of thyristors :

The junction temperature and decreasing internal resistance . This in turn increases

its current sharing and may damage the thyristor .

This thermal runaway may avoided

By having common heat ,so that all units operate at the temperature.

PARALLEL OPERATION OF THYRISTOR

A small resistance ,as shown in figure may be connected in series with each the thyristor to force equal current sharing ,but they may be considerable power loss in the series resistances .

A common approach for current sharing is to be use magnetically coupled inductors .

PARALLEL OPERATION OF THYRISTOR

If the current through thyristor T1 increases, a voltage of opposite polarity can be induced in the winding of the thyristor T2 and impedance through the path of T2 can be reduced , their by increasing the current flow through T2.

PARALLEL OPERATION OF THYRISTOR

Due to unequal current division, current through SCR increases, its temp also increases by this , decreases the resistance.

Hence further increase in current takes place & this is a cumulative process, known as thermal , run away , which can damage the device.

To overcome this problem SCRs would be maintained at same temp. This is possible by mounting them on same heat sink.

PARALLEL OPERATION OF THYRISTOR

PARALLEL OPERATION AS CURRENT AND PHASE CONTROL CCT

PARALLEL OPERATION AS CURRENT AND PHASE CONTROL CCT WITH OSC.

PARALLEL OPERATION AS CURRENT AND PHASE CONTROL CCT

PARALLEL OPERATION AS CURRENT AND PHASE CONTROL CCT WITH OSC.

PARALLEL OPERATION AS CURRENT AND PHASE CONTROL CCT

PARALLEL OPERATION AS CURRENT AND PHASE CONTROL CCT WITH OSC.

PARALLEL OPERATION AS CURRENT AND PHASE CONTROL CCT

PARALLEL OPERATION AS CURRENT AND PHASE CONTROL CCT WITH OSC.

VIEW OF OSCILLOSCOPE OUTPUTSOF PHASE CONTROL CCT

PARALLEL OPERATION OF THYRISTORS

Once the GTO thyristor is turned on, forwardgate current must be continued for hole of theconduction to ensure the device remains inconduction .

Other wise the device cannot remain inconduction during the on state period ,it will be inthe off state (GTO will be not in saturation state) .

PARALLEL OPERATION OF THYRISTORS AS A CURRENT CONTROLLER IN UPS

PARALLEL OPERATION OF GTO THYRISTORS AS WORKING IN H. BRIDGE (UPS)

PARALLEL OPERATION OF THYRISTORS.

When we give the output of oscillator to the parallel fitted of thyristors to gate as shown in H . Bridge .

Positive voltages are given via C.T Transformer to anode and Negative battery voltages are given via fuse at the Cathode of GTO at two sides of the H . Bridge.

When positive voltages or pulse will appear On the Gate thyristor will conduct ,otherwise it will not conduct as off state.

GTO THYRISTORS IN UPS WORLD CHALLING ENERGY SOURCE

Any Question.