I’ve been brought out of Superhero retirement to help our current and future customers in any way I can. Since Superheroes don’t age, I still look the same as I did some 40 years ago, for those of you who may remember me.
Maximum motor lead length when using AC Drives
All drives are limited with respect to the maximum motor lead length that they can support. This limitation occurs because the drive must supply additional current to charge or discharge cable capacitance. Maximum Cable length recommendations are different for different Series Drives.
The use of an output reactor is usually the most convenient and economical means of minimizing the possibility of motor insulation failure due to the voltage stress caused by the interaction between the inverter waveform, the motor cable and the connected motor.
Here is a series of Best Practices to help mitigate problems caused by excess lead length.
– Always use the lowest Carrier Frequency possible – higher carrier Frequency results in shorter Insulation life.
Example : 150 foot long cable Motor insulation life is reduced from 100000 hours to
25000 hours when carrier frequency is increased from 3 KHz to 12 KHz
– Use Motors that meet NEMA MG-1 Part 31 – with 1600 volt rated Insulation and
Insulation between phases.
– Use VFD Cable – ideally with Symmetrical Ground.
When selecting cable type and wiring methods consult the drive manufacturer’s manuals for their recommendations and the motor manufacturer for their recommendations. Longer cable runs may require an output filter dependent on the drive horsepower and the motor voltage and motor winding’s insulation peak voltage withstand rating.
For help navigating this confusing topic call us at 630-595-1010 and me and my Flolo friends will be there to assist you because our goal is “Keeping your future in motion”.