Method and apparatus detecting a failed thyristor

A method of detecting a failed short thyristor in a solid-state controller for delivering power to a load during reduced-voltage operation, said method comprising:

• detecting a voltage across the thyristor with a voltage detector comprising a resistor, a capacitor, and a light emitting diode, wherein the capacitor is configured to limit the current through the resistor and the light emitting diode;
• and
• indicating a failed short thyristor when the absolute value of the voltage across the thyristor remains below a threshold value during a predetermined period of time.

An apparatus for detecting a failed short thyristor in a solid-state controller for delivering power to a load during reduced-voltage operation, said apparatus comprising:

• means for detecting a voltage across the thyristor with a voltage detector comprising a resistor, a capacitor, and a light emitting diode, wherein the capacitor is configured to limit the current through the resistor and the light emitting diode;
• and
• means for indicating a failed short thyristor when the absolute value of the voltage across the thyristor remains below a threshold value during a predetermined period of time.

An apparatus for detecting a failed open thyristor in a solid-state controller for delivering power to a load during full-voltage operation, said apparatus comprising:

• a voltage detector circuit comprising a resistor, a capacitor, and a light emitting diode for detecting a voltage across the thyristor;
• and
• a microprocessor optically coupled to the voltage detector circuit for indicating a failed open thyristor when the absolute value of the voltage across the thyristor exceeds a threshold value.

A method of detecting a failed open thyristor in a solid-state controller for delivering power to a load during full-voltage operation, said method comprising:

• detecting a voltage across the thyristor;
• and
• indicating a failed open thyristor when the absolute value of the voltage across the thyristor exceeds a threshold value.

An apparatus for detecting a failed open thyristor in a solid-state controller for delivering power to a load during full-voltage operation, said apparatus comprising:

• means for detecting a voltage across the thyristor;
• and
• means for indicating a failed open thyristor when the absolute value of the voltage across the thyristor exceeds a forward threshold voltage.