Not only VFD/DC drives, any power converter having nonlinear rectifier (Diode based or Thyristor based) for input power conversion can generate line harmonics in the system. Basically, whenever there is number of nonlinear load running in the system it can experience high level of harmonics. Improper distribution of load can also create high neutral current with high third harmonics in Europe and India where there is a neutral. For motor coil burning MachineSense PA will measure voltage/current imbalance and with an intelligent algorithm will send you a SMS/Email notification if there is a trace of Motor Coil failure.) Effect of high current harmonics in motor input line:Ĭurrent harmonics are generated by use of SMPS based power adapters such as LEDs in the factory. (To measure Undervoltage, Load and Current imbalance you can use MachineSense PA. If one of the winding gets partially damaged, its winding impedance will change and will try to create magnetic imbalance which in turn will create current imbalance. Voltage imbalance has the same impact as that of the under voltage. This additional current can create additional heating of the coil. Under voltage in the line increasesthe current drawn by that line when the motor is running on constant load (power mode). In the long run, insulation can get damaged and inter-turn ( a portion of the winding) can be short circuited/burnt.Įffect of high current imbalance in motor input line: Current waveform gets distorted and more importantly peak can even go beyond fundamental peak which unneccessairily increases heating of the coil.
4 shows how the impact of high harmonics generated by VFD keeps on going to the normal motors attached to the same electrical panel. Whereas current gets filtered with motor inductance and it looks like sinewave. when speed requirement is less, frequency gets low like conveyer belt. It is clear that voltage at VFD output is a SPWM output which can vary with time depending upon load demand i.e. 3 tells about the phase voltage and current waveforms at the VFD output. These harmonics generated by VFD can affect other motors running parallel to same electrical panel output. It is the current waveform which is highly distored and can carry up to 90% harmonics of different frquencies (100Hz, 150Hz, 200Hz…so on). 2 shows typical voltage and current input at VFD input when VFD is having diode rectifier or thyristorized rectifier at input for the conversion of AC-DC. In most cases it is the same electrical panel where VFD is taking power to run motor and also some medium size motors are attached to it. 1 shows motors are connected with VFD system and Utility directly in a factory.
4: Phase current of the motor (M1) input due the presence of VFD nearby
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