Electrical net enterprise in order to ensure the normal operation of production line, speculative protection is particularly important, for regular maintenance is to prevent electrical outages, forming production line of huge loss. Many businesses will do speculative insulation protection regularly, but despite the timing for insulation detection, motor will damage due to insulation problem, is this why? Let's find out eventually. Set to introduce fujian municipal water group, the fruit of the department as a municipal county water supply security products, production department can do it in front of the motor operation practice of temperature, insulation function view. But this kind of practice view does not prevent accidental burning of the motor. 2005 device of motor operation 6 years burned down in 2012, 2012 device of motor operation 6 years in June 2018, and the two motors are winding burn. Why the two motors are winding burn out, the insulation of the traditional test instrument can't find the insulation of the motor winding problem? Let's look at the end and motor voltage converter output. Experimental examples using FlukeMDA -(1) - 550 test(4) test is a variable frequency motor, frequency converter and motor cable length is between 20 m, from here, the motor of the burr, peak increases, changed from the original 1240 v to 1790 v, overshoot by 14. By 7% to 80. 1%. (5) the inverter output waveform analysis and motor end figure 5 test for power frequency of the motor, the motor is burned in June 2018 after the repair of motor, the motor insulation heat resistant to F grade, to allow the highest working temperature is 155 ℃, between the inverter and motor cable length is 2 m, the MDA -500, motor of the peak voltage of 900 v, overshoot coefficient was 67%, the pulse impulse voltage has reached the IEC standard & other; Harsh & throughout; Level. Case analysis by figure 5 measurement result shows that the motor operates fengfeng value of voltage is 1640 v, and & other; General IVICA” Insulation level of the frequency converter, motor maximum value is 1254 v, it is the long pulse over-voltage turn-to-turn insulation in motor function decline, resulting in short circuit breakdown, the motor burned. For this condition, claims to choose frequency conversion motor, impulse insulation level at least & other; Medium IVICB” 。 Conclusion of traditional insulation resistance test instrument can only measure facies, the insulation of the phase to phase function, and each phase itself it is impossible to assess the turn-to-turn insulation, which is why even with traditional insulation testing regularly, there will be formed as a result of insulation problem motor burning phenomenon. To this, the pulse voltage at the motor, the overshoot coefficient detection is particularly important, and a detection, this can achieve the goal of speculative protection, prevent to produce line bring the huge economic loss.
