Which condition should be met for an SCR to turn off?

For an SCR (Silicon Controlled Rectifier) to turn off, the holding current must be removed. The holding current is the minimum current that must flow through the SCR to keep it in the conducting state once it has been turned on. If the current falls below this level, the SCR will cease to conduct and turn off. This behavior is crucial in controlled rectifier applications, where precise control of the power delivered to the load is required.

While other conditions such as excessive forward current or changes in temperature may affect the operation of the SCR, they do not directly determine whether the device can turn off. Disconnecting all power supply circuits would typically be a drastic action and not a routine operational requirement for turning off the SCR.