HOLDING CURRENT

HOLDING CURRENT
It is the maximum anode current, gate being open, at which SCR is turned off from ON conditions.

When Semi conductor Rectifier is in the conducting state, it cannot be turned OFF even if gate voltage is removed.  The only way to turn off or open the SCR is to reduce the supply voltage to almost zero at which point the internal transistor comes out of saturation and opens the SCR.  The anode current under this condition is very small (few mA) and is called Holding current.  If an SCR has a holding current of 5mA, it means that if anode current is made less than 5mA, then SCR will be turned off.

PEAK REVERSE VOLTAGE

PEAK REVERSE VOLTAGE
It is the maximum reverse voltage (cathode positive w.r.t anode) that can be applied to an SCR without conducting in the reverse direction.

Peak reverse voltage(PRV) is an important consideration while connecting an SCR in an a.c circuit. During the negative half of a.c supply, reverse voltage is applied across SCR.  If PRV is exceeded, there may be avalanche breakdown and the SCR will be damaged if the external circuit does not limit the current.  

BREAKOVER VOLTAGE

BREAKOVER VOLTAGE
It is the minimum forward voltage, gate being open, at which  Semi Conductor Rectiver(SCR) starts conducting heavily i.e turned on

if the breakover voltage of an SCR is 220V, it means that it can block a forward voltage as long as the supply voltage is less than 220V.  If the supply voltage is more than this value, the SCR will be turned on.  In practice SCR is operated with supply voltage less than breakover voltage and it is then turned on by means of a small voltage applied to the gate.

SILICON CONTROLLED RECTIFIER (SCR)

SILICON CONTROLLED RECTIFIER (SCR)
is a semiconductor device that acts as a true electronic switch.  It can change alternating current into direct current and at the same time can control the amount of power fed to the load.  SCR combines the features of a rectifier and a transistor.