VOLTAGE RATINGS
· VDWM : This specifies the peak off state working forward voltage of the device. This specifies the maximum forward off state voltage which the thyristor can withstand during its working.
· VDRM : This is the peak repetitive off state forward voltage that the thyristor can block repeatedly in the forward direction (transient). Power Electronics 10EC73 SJBIT/Dept of ECE Page 67
· VDSM : This is the peak off state surge / non-repetitive forward voltage that will occur across the thyristor.
· VRWM : This the peak reverse working voltage that the thyristor can withstand in the reverse direction.
· VRRM : It is the peak repetitive reverse voltage. It is defined as the maximum permissible instantaneous value of repetitive applied reverse voltage that the thyristor can block in reverse direction.
· VRSM : Peak surge reverse voltage. This rating occurs for transient conditions for a specified time duration.
· VT : On state voltage drop and is dependent on junction temperature.
· VTM : Peak on state voltage. This is specified for a particular anode current and junction temperature. dv dt rating: This is the maximum rate of rise of anode voltage that the SCR has to withstand and which will not trigger the device without gate signal (refer dv dt triggering).
CURRENT RATING
· ITaverage : This is the on state average current which is specified at a particular temperature.
· ITRMS : This is the on-state RMS current.
· Latching current, IL : After the SCR has switched on, there is a minimum current required to sustain conduction. This current is called the latching current. IL associated with turn on and is usually greater than holding current
· Holding current, IH : After an SCR has been switched to the on state a certain minimum value of anode current is required to maintain the thyristor in this low impedance state. If the anode current is reduced below the critical holding current value, the thyristor cannot maintain the current through it and reverts to its off state usually Iuis associated with turn off the device.
· di/dt rating: This is a non repetitive rate of rise of on-state current. This maximum value of rate of rise of current is which the thyristor can withstand without destruction. When thyristor is switched on, conduction starts at a place near the gate. This small area of conduction spreads rapidly and if rate of rise of anode current di/dt is large compared to the spreading velocity of carriers, local hotspots will be formed near the gate due to high current density. This causes the junction temperature to rise above the safe limit and the SCR may be damaged permanently. The di/dt rating is specified in A/µsec
· VDWM : This specifies the peak off state working forward voltage of the device. This specifies the maximum forward off state voltage which the thyristor can withstand during its working.
· VDRM : This is the peak repetitive off state forward voltage that the thyristor can block repeatedly in the forward direction (transient). Power Electronics 10EC73 SJBIT/Dept of ECE Page 67
· VDSM : This is the peak off state surge / non-repetitive forward voltage that will occur across the thyristor.
· VRWM : This the peak reverse working voltage that the thyristor can withstand in the reverse direction.
· VRRM : It is the peak repetitive reverse voltage. It is defined as the maximum permissible instantaneous value of repetitive applied reverse voltage that the thyristor can block in reverse direction.
· VRSM : Peak surge reverse voltage. This rating occurs for transient conditions for a specified time duration.
· VT : On state voltage drop and is dependent on junction temperature.
· VTM : Peak on state voltage. This is specified for a particular anode current and junction temperature. dv dt rating: This is the maximum rate of rise of anode voltage that the SCR has to withstand and which will not trigger the device without gate signal (refer dv dt triggering).
CURRENT RATING
· ITaverage : This is the on state average current which is specified at a particular temperature.
· ITRMS : This is the on-state RMS current.
· Latching current, IL : After the SCR has switched on, there is a minimum current required to sustain conduction. This current is called the latching current. IL associated with turn on and is usually greater than holding current
· Holding current, IH : After an SCR has been switched to the on state a certain minimum value of anode current is required to maintain the thyristor in this low impedance state. If the anode current is reduced below the critical holding current value, the thyristor cannot maintain the current through it and reverts to its off state usually Iuis associated with turn off the device.
· di/dt rating: This is a non repetitive rate of rise of on-state current. This maximum value of rate of rise of current is which the thyristor can withstand without destruction. When thyristor is switched on, conduction starts at a place near the gate. This small area of conduction spreads rapidly and if rate of rise of anode current di/dt is large compared to the spreading velocity of carriers, local hotspots will be formed near the gate due to high current density. This causes the junction temperature to rise above the safe limit and the SCR may be damaged permanently. The di/dt rating is specified in A/µsec
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