Method for detecting output phase loss of frequency converter

The invention, which relates to the field of frequency conversion speed regulation, discloses a method for detecting the output phase loss of a frequency converter. The method comprises the followingsteps that: a three-phase instantaneous current output value of a frequency converter is sampled and a three-phase instantaneous current integrated vector effective value is calculated; a step A is performed; to be specific, an absolute value of an instantaneous current output value of each phase is compared with a first phase loss threshold respectively; if the absolute value of the current instantaneous current output value is less than the first phase loss threshold, the phase variable of the phase is unchanged and a first time length is accumulated; when the first time length is larger than a first time length threshold and an absolute value of the difference between the phase variable and a motor electrical angle is greater than 90 degrees, the output phase loss of the current phase is determined; and if the absolute value of the current instantaneous current output value is greater than or equal to the first phase loss threshold, the current phase variable is synchronized to be acurrent motor electrical angle and the first time length is reset; and a step B is performed; to be specific, the three-phase instantaneous current integrated vector effective value is compared witha second phase loss threshold; if the three-phase instantaneous current integrated vector effective value is less than the second phase loss threshold, a second time length is accumulated; when the second time length is larger than or equal to a second time length threshold, the three-phase output phase loss is determined; and if the three-phase instantaneous current integrated vector effective value is larger than or equal to the second phase loss threshold, the second time length is reset.