# How do I test a SCR for Peak Reverse Blocking Voltage on my curve tracer?

### 問題：

How do I test a SCR for Peak Reverse Blocking Voltage on my curve tracer?

### 答案：

Peak Reverse Blocking Voltage - VRRM

What It Is:

With no gate signal applied, peak reverse blocking voltage is the maximum reverse voltage that can be applied to the anode without causing reverse anode current in excess of the specified maximum.  Peak reverse blocking voltage is equal to peak forward blocking voltage but of opposite polarity.

On the curve tracer, the anode is connected to the Collector Supply and the gate is held open.

What The Display Shows:

The display shows anode voltage on the horizontal axis, and the resulting anode current on the vertical axis.  The specification is met when the specified reverse voltage can be applied without causing reverse current in excess of the specified maximum.

How To Do It:

1. Set controls:

A: Max Peak Volts to the lowest setting above the specified VRRM

B: Max Peak Power Watts to the lowest setting that satisfies (IRRM x VRRM)

C: Horizontal Volts/Div to display VRRM between the 5th and 10th horizontal divisions

D: Vertical Current/Div to display IRRM between the 5th and 10th vertical divisions

E: Collector Supply Polarity to -DC

F: Configuration to (Base/Open, Emitter/Common)

K: Variable Collector Supply to minimum % (full ccw)

L: Dot Cursor (On)
2. Apply power to the SCR:

A: Position the Left/Right switch as appropriate

B: Slowly increase Variable Collector % until the specified VRRM is attained

3. Compare to data sheet specifications:

A: Check that at the specified VRRM, IRRM is less than or equal to the specified maximum