How do I test a SCR for Peak On-State Voltage on my curve tracer?
Peak On-State Voltage - VTM
What It Is:
Peak on-state voltage is the anode voltage with the device in the unblocked (On) state
and ID at a specified value.
On the curve tracer, the anode is driven by the Collector Supply and the gate is driven by the step generator. The test is made by applying the specified gate current or voltage, then slowly increasing anode voltage until the SCRswitches to the unblocked (On) state and the specified ID is attained.
What The Display Shows:
VD is displayed on the horizontal axis, and the resulting ID is displayed on the vertical axis. The specification is met when at the specified ID, VD is less than or equal to the specified maximum.
How To Do It:
1. Set controls:
A: Max Peak Volts to the lowest setting
B:Max Peak Power Watts to the lowest setting that limits ID to the specified value
C: Horizontal Volts/Div to display VD between the 5th and 10th horizontal divisions
D: Vertical Current/Div to display the specified ID between the 5th and 10th vertical divisions
E: Collector Supply Polarity to +DC
F: Configuration to (Base/Step Gen, Emitter/Common)
G: Variable Collector Supply to minimum % (full ccw)
H: Number of steps to minimum (zero)
I: Pulse to Short
I: Step Generator to Current (or Voltage)
J: Step Generator polarity to +
K: Step/Offset Amplitude to approx 50% of the specified value of gate drive
L: Variable Collector Supply % to minimum (full ccw)
2: Apply gate drive:
A: Position the Left/Right switch as appropriate
B: Press Offset Aid to gradually increase IG (or VG) to the specified value
3. Apply power to the SCR:
Slowly increase the Variable Collector Supply % until the device switches to the unblocked (On) state and the specified ID is attained.
4. Compare to data sheet specifications:
Check that VD is less than or equal to the specified maximum.
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