Descriptions of symbols used in SCR device specifications:

VDRM: Peak repetitive forward off-state voltage
VRRM: Peak repetitive reverse voltage
VDSM: Peak non-repetitive forward off-state voltage
VRSM: Peak non-repetitive reverse voltage
VTM: Maximum on-state voltage
VTO: On-state threshold Voltage
VISO: Isolation voltage
VGT: Gate trigger voltage

IT(AV): Average on-state current
IF(AV): Average forward current
IDRM: Peak repetitive forward off-state current
IRRM: Peak repetitive reverse current
ITRMS: On-state RMS current
ITM: Peak on-state current
ITSM: Peak non-repetitive surge current within a wave period
IGT: Gate trigger current
IH: Holding current
I2t: Current square time

Tq: Turn-off time
trr: Reverse recovery time
THS: Heat-sink temperature
Tj: Junction temperature
Tjm: Rated junction temperature
Tg: Ambient junction temperature
dv/dt: Critical off-state voltage rising rate
di/dt: Critical on-state current rising rate
Rt: On-state slope resistance
Rth(j-hs): Thermal resistance (junction to heat-sink)
Rth(j-C): Thermal resistance (junction to case)
Qr: Reverse recovery charge
L*p: Light trigger sensitivity.

◆◆ SCR Devices
Average On-state Current (IT): At an ambient temperature of +40℃ and specified cooling conditions and with the device connected to a resistive single-phase commercial-frequency half sine-wave circuit with a turn-on angle no less than 170°, indicates the maximum average on-state current when the junction temperature is stabilized and not exceeds the rated junction temperature.

Peak Non-Repetitive Forward Off-state Voltage (VDSM): indicates the peak off-state voltage corresponding to the sharp corner on the forward I-V characteristic curve when the gate is turned off.

Peak Repetitive Forward Off-state Voltage (VDRM): equivalent to 90% of the Peak Non-Repetitive Forward Off-state Voltage.

Average Non-Repetitive Forward Off-state Current (IDS): indicates the average leak current corresponding to the Peak Non-Repetitive Forward Off-state Voltage at the rated junction temperature when the gate is turned off.

Average Repetitive Forward Off-state Current (IDR): indicates the average leak current corresponding to the Peak Repetitive Forward Off-state Voltage.

Gate Trigger Current (IGT): at room temperature and with a main voltage of 6 VDC, indicates the minimum gate DC current necessary to completely turn on the device.

Gate Trigger Voltage (VGT): indicates the gate DC voltage corresponding to the gate trigger current.

Critical Off-state Voltage Rising Rate (dv/dt): at the rated junction temperature and with the gate turned off, indicates the minimum voltage rising rate that change the device from off-state to on-state.
◆◆ TRIAC Devices
On-state Current (IT): At an ambient temperature of +40℃ and specified cooling conditions and with the device connected to a resistive single-phase commercial-frequency half sine-wave circuit, indicates the maximum RMS on-state current when the junction temperature is stabilized and not exceeds the rated junction temperature.

Critical Current Dropping Rate for Reversal (di/dt)c: indicates the maximum on-state current dropping rate for the device to reverse from on-state to a reversed direction.

Gate Trigger Current (IGT): at room temperature, with a main voltage of 12 VDC and triggered by gate, indicates the minimum gate DC current necessary to completely turn on the device.
◆◆ Quick SCR Devices
Gate-controlled Turn-on Time (tgt): at room temperature and with a specified gate impulse current to turn the device from off-state to on-state, indicates the required time from the specified point on the leading edge of the gate impulse to the point where the main voltage reaches to the specified low level.
Circuit Reversal Turn-off Time (tq): indicates the time period from the moment when the on-state current drops to zero to the moment when the device is able to endure the specified off-state voltage.