Test: Thyristor Mounting - Electrical Engineering (EE) MCQ

Pilot SCR is an SCR which is fired which activates the firing circuit and fires the main SCR.

Inter-digitating is the inter-mixing of the gate-cathode area to improve the di/dt ratings. di/dt rating is improved by providing more cathode conduction area during the delay and rise time.

Cathode shorts are realized by overlapping metal on cathode n+ layers with a narrow p-region in between.

θ_jA = θ_jc+ θ_cs+ θ_sA.

The case-to-sink thermal resistance depends on the size of the device, pressure, grease between the interface, etc.

It does not depend on any of the device configurations.

: P_av = (T_j – T_a)/θ_jA
θ_jA = (θ_jc + θ_cs + θ_sA).

Heat DISSIPATION (rejection of heat to the atmosphere) takes place through convention only.

Lead mounting is a very simple time of mounting used for low power devices.

 In the press-pak type the device is pressed or clamped between two heat-sinks & external pressure is applied from both the sides.