Voltages in transistor

Key Electrical High-Voltage Testing Terms

1) Threshold Voltage (Vth or Vgs):
The minimum gate-to-source voltage required in a Field Effect Transistor (FET) to establish a conductive path between the source and the drain terminals. Below this value, the transistor remains in a non-conductive state.

2) Withstand Voltage:
The maximum voltage that an insulating material or electrical component can sustain without losing its dielectric strength. Exceeding this voltage causes electrical breakdown or permanent damage to the insulation.

3) 100% Flashover Voltage:
The voltage level at which a flashover occurs every time the test voltage is applied under specified conditions. It represents the certain flashover point for the test object.

4) 50% Flashover Voltage:
The voltage at which there is a 50% probability of flashover occurring under specified conditions when applied repeatedly. Often used in statistical testing of insulators and equipment.

5) AC Test Voltage:
An alternating voltage of power frequency (40–60 Hz), nearly sinusoidal in waveform, applied to an electrical component for testing its dielectric strength and insulation performance.

6) Creeping Distance:
The shortest path along the surface of an insulator between two conductive parts. It is critical for preventing surface leakage currents and flashovers, especially in polluted or humid environments.

7) Impulse Voltage:
A short-duration, high-magnitude voltage characterized by:

• Peak value

• Time to front (rise time)

• Time to half-value (decay time)
  Impulse voltages simulate lightning or switching surges in testing.

8) Disruptive Discharge Voltage:
The voltage at which the dielectric strength of insulation is lost, resulting in a complete breakdown. It is the critical stress point where the insulation fails under electrical stress.