# How do I test a SCR for Holding Current on my curve tracer?

### 問題：

How do I test a SCR for Holding Current on my curve tracer?

### 答案：

Holding Current - IH

What It Is:

With the device in the unblocked (On) state, holding current is the minimum value of anode current required to keep it in the on-state, with gate drive removed.

On the curve tracer the Collector Supply drives the anode and the Step Generator drives the gate.

What The Display Shows:

The display shows VDS on the horizontal axis, and the resulting ID on the vertical axis.  The specification is met when with gate drive removed, the ID required to keep the device in the unblocked (On) state is less than or equal to the specified maximum.

How To Do It:

1. Set controls:

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

B: Max Peak Power Watts to the lowest setting that satisfies (ID x VDS)

C: I: Collector Supply Polarity to +DC

D: Horizontal Volts/Div to display VD between the 5th and 10th horizontal divisions

E: Vertical Current/Div to display ID between the 5th and 10th vertical divisions

F: Number of steps to minimum (zero)

G: Step Generator to Current (or Voltage)

H: Step Generator Polarity to +

I: Step/Offset Ampl to approx 50% of the specified gate drive

J: Pulse to Long

K: Configuration to (Base/Step Gen, Emitter/Common)

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

M: DotCursor ON

2. Apply power to the SCR:

A: Position the Left-right switch as appropriate

B: Slowly increase the Variable Collector Supply until the specified VD is attained

3: Apply gate drive:

Press and hold Offset Aid until the device switches to the unblocked (On) state

4. Remove gate drive:

Simultaneously press Aid and Oppose to remove gate drive

5: Reduce VD:

Slowly decrease Variable Collector % and note the minimum value of ID reached before the devices switches to the blocked (Off) state - this is the holding current

6. Compare to data sheet specifications:

A: Check that IH is less than or equal to the specified maximum