Premature insulation failures from voltage spikes lead to the early death of most inverter-fed motors. Sure, there have been attempted "cures" implemented by other motor makers to extend insulation life: special spike-resistant magnet wire, premium insulation, etc. But the truth is, partial corona discharges kill insulation, and until corona is eliminated, inverter-duty motors will continue to fail before their time.
WHAT IT TAKES TO SURVIVE: THE MOST
COMPREHENSIVE DEFENSE AGAINST VOLTAGE SPIKES
Voltage spikes from IGBT-based VFD's will always be with us. The trick is to design and make a motor insulation system that keeps the spikes from developing corona. To keep corona from occurring, a motor's Corona Inception Voltage or CIV must be higher than the maximum
voltage the motor will experience. Lincoln motors have achieved this breakthrough by utilizing a better design, better materials and better manufacturing methods. These are key elements of Lincoln's Ultimate Spike DefenseTM Insulation System.
MOTOR DESIGN: WINDING
Most Lincoln motors are in-slot wound. Why?
| In a motor winding which has been random wound or coil-inserted, there is a likelihood that the beginning turns and endings turns of a coil could be in close proximity to each other. Because of the uneven voltage distribution in the coil caused by the high voltage transients, this close proximity can serve as a point where voltage potential is very high between adjacent turns. This situation often results in an area where corona degradation begins. However, if the turns of a coil are placed in the stator slot sequentially (as in a form wound or in-slot wound stator), there is substantially decreased probability that beginning and ending turns could be close to one another within the winding. |
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MOTOR DESIGN: TEMPERATURE
Lincoln motors are designed to run cool. Why?
Operating temperature has a definite effect on the CIV of an insulation system. It has been shown that the CIV of a twisted pair at 155oC (maximum stabilized temperature of a motor constructed with Class F insulation) is substantially lower than the CIV of the same twisted pair at room temperature. Therefore, a cool running motor is desirable over one that operates at a high temperature.
MOTOR MATERIALS: VARNISH
Lincoln motors are multiple-dipped in a Class H, solvent-based varnish. Why?
Another process which affects the CIV of a motor is the varnishing of the stator. Varnish is used for various reasons, but one of its primary purposes is to increase the dielectric strength of the insulation system. Greater varnish build (through multiple dips in a dip and bake
system) within a winding gives the winding a higher CIV, resulting in a greater resistance to high voltage transients.
MOTOR MATERIALS: PHASE PAPER
Lincoln motors use generous amounts of premium phase paper. Why?
A motor without phase paper will have a lower CIV than an identical motor built using this type of added insulation protection because of the reduced amount of material between separate phases of the winding.
MOTOR MATERIALS: MAGNET WIRE
Lincoln uses the latest spike-resistant wire. Why?
The advanced technology magnet wires introduced several years ago promise an improved ability to endure the high voltage pulses experienced with IGBT wave forms. However, the new wire does nothing to eliminate fast voltage rise times (overshoot) and voltage reflections caused by the inverter drive. Better wire helps, but when employed as the sole spike defense (typical of some other motor manufacturers), it only postpones the inevitable motor failure. The full benefit of special wire is realized only when it is an integral part of a total system approach to stop insulation damage...the way we do at Lincoln!
MOTOR MANUFACTURING TECHNIQUES
Lincoln minimizes the potential for magnet wire insulation damage during manufacture by dispensing wire from its original packaging directly into the stator slot. Why?
In general, the basic quality of manufacturing processes contributes to the CIV of a motor. If magnet wire is damaged (even slightly) at any stage of construction, that area could likely become a corona inception point in future motor operation. In many cases, these small nicks are not detectable by a surge test process, and will not be discovered until after motor failure has occurred. For this reason, exceptional care is taken by Lincoln in the construction of inverter-duty motors.
SPECIFY LINCOLN VTAC AND CTAC MOTORS
Lincoln VTAC and CTAC motors are uniquely qualified to meet the most demanding inverter duty motor specifications and the Ultimate Spike Defense Insulation System is the reason why. It's also the reason we can stand behind our motor with a precedent-setting five year warranty. So, the next time you want the ultimate answer for trouble-free, extended-life motor operation...specify Lincoln.
