Cutting or welding system having phase loss detector and method of detecting phase loss for same

A method of detecting phase loss in a power source of a cutting or welding system comprising:

• filtering an electrical signal representative of a voltage so that only a ripple voltage passes therethrough;
• blocking the ripple voltage below a predetermined threshold;
• and
• disabling the power source responsive to the ripple voltage exceeding a predetermined threshold.

A power source for providing electrical power to a cutting or welding system including a cutting or welding torch, said power source comprising:

• an electrical input line which receives electrical power from an external power supply;
• a transformer having a primary side connected to said electrical input line and a secondary side;
• a rectifier operatively connected to said secondary side of said transformer;
• an output line operatively connected to said rectifier for providing the electrical power to the torch;
• a bias supply circuit comprising auxiliary windings operatively coupled to said primary side of said transformer, and a rectifier circuit connected to said auxiliary windings so that said bias supply circuit generates a rectified electrical output signal different from the electrical power provided to the torch;
• and
• a phase loss detecting circuit operatively connected to said bias supply circuit which detects a ripple portion of said rectified electrical output signal and which determines a phase loss condition when said ripple portion exceeds a predetermined threshold.

A cutting or welding system comprising:

• a cutting or welding torch;
• and
• a power source operatively coupled to said torch, said power source comprising;
• an electrical input line which receives electrical power from an external power supply,
• a transformer having a primary side connected to said electrical input line and a secondary side,
• a rectifier operatively connected to said secondary side of said transformer,
• an output line operatively connected to said rectifier for providing the electrical power to the torch,
• a bias supply circuit comprising auxiliary windings operatively coupled to said primary side of said transformer, and a rectifier circuit connected to said auxiliary windings so that said bias supply circuit generates a rectified electrical output signal different from the electrical power provided to the torch, and
• a phase loss detecting circuit operatively connected to said bias supply circuit which detects a ripple portion of said rectified electrical output signal and which determines a phase loss condition when said ripple portion exceeds a predetermined threshold.

A power source for providing electrical power to a cutting or welding system including a cutting or welding torch, said power source comprising:

• an electrical input line which receives electrical power from an external power supply;
• a transformer having a primary side connected to said electrical input line and a secondary side;
• a rectifier operatively connected to said secondary side of said transformer;
• an output line operatively connected to said rectifier for providing the electrical power to the torch;
• and
• a phase loss detecting circuit coupled to said transformer, wherein said phase loss detecting circuit detects a ripple portion of said rectified electrical output signal and determines a phase loss condition when said ripple portion exceeds a predetermined threshold, and wherein said phase loss detecting circuit includes,
• a filter which blocks a DC portion of said rectified electrical output signal and allows said ripple portion to pass,
• a blocking circuit which blocks said ripple portion when said ripple portion is below said predetermined threshold and which passes said ripple portion when said ripple portion exceeds said predetermined threshold wherein said filter and blocking circuit are arranged in a serial relationship, and
• a detector which detects that said ripple portion exceeding said predetermined threshold has been passed by said blocking circuit to determine the phase loss condition.