NP−SCMC Series

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4

ELECTRICAL PARAMETER/RATINGS DEFINITIONS

Symbol

Parameter

Repetitive Peak Off−state Voltage

Breakover Voltage

Off−state Current

Breakover Current

Holding Current

On−state Voltage

On−state Current

Nonrepetitive Peak On−state Current

Nonrepetitive Peak Impulse Current

Off−state Voltage

Off−state Current

Figure 1. Voltage Current Characteristics of TSPD

−Voltage

+Voltage

−I

+I

Off−State Region

TIME (ms)

0

50

0

100

Peak

Value

Half Value

1

10

100

0.1

1

10

100

1000

Figure 2. Nonrepetitive On−State Current vs. Time

Figure 3. Nonrepetitive On−State Impulse vs.

CURRENT DURATION (s)

Detailed Operating Description

The TSPD or Thyristor Surge Protection Device are

specialized silicon based overvoltage protectors, used to

protect sensitive electronic circuits from damaging

overvoltage transient surges caused by induced lightning

and powercross conditions.

The TSPD protects by switching to a low on state voltage

when the specified protection voltage is exceeded. This is

known as a “crowbar” effect. When an overvoltage occurs,

the crowbar device changes from a high−impedance to a

low−impedance state. This low−impedance state then offers

a path to ground, shunting unwanted surges away from the

sensitive circuits.

This crowbar action defines the TSPD’s two states of

functionality: Open Circuit and Short Circuit.

Open Circuit – The TSPD must remain transparent during

normal circuit operation. The device looks like an open

across the two wire line.

Short Circuit – When a transient surge fault exceeds the

TSPD protection voltage threshold, the devices switches on,