Standard Motor Catalog

Section TR Technical Reference Guide

Effects of CIV, depend on construction and process adopted during manufacturing; few are listed below: 1. Winding: CIV improves if the beginning turn and ending turn are not in close proximity 2. Varnish and Resin: CIV improves with the increase in number of ‘dip and bake’ or ‘VPI’ system or excellent varnish impregnation through trickle-treat. 3. Phase Paper: Introduction of phase paper between the different phases, improves CIV, which are a standard feature for GE’s Polyphase motors. AMBIENT As a standard offering, GE motors are rated for maximum ambient of +40°C. For high and low ambient, refer to page TR.47. GE stock XSD Ultra ® motors, generally are rated for dual ambient, as follows: At ambient 40°C, Class H with temperature rise limited to 80°C at 1.0 Service Factor and suitable for 1.25 Service Factor with 115°C rise. Alternatively these motors are suitable for operation in a 65°C ambient with 105°C rise, at 1.0 Service Factor.

It is to be noted that for the subject test motor is equipped with special grease and or bearings. If need arises, the bearing system of the test motor, is overhauled. CORONA INCEPTION VOLTAGE (CIV) The CIV is the voltage at which partial discharges begin occurring within small voids inherent in any insulation system, for random winding which id fed by IGBT drive. When the voltage stress across these voids reaches the CIV, a discharge of energy takes place. These partial discharges can cause degradation of the insulation system through both chemical and mechanical erosion. Clearly, if a motor is operating continuously at a level of voltage stress above its CIV, insulation degradation occurs and eventually leads to motor failure. CIV can be controlled: 1. Externally by: • Introducing power conditioning accessories like filters, reactors and isolation transformers. • Restricting the distance (lead length), between the motor and drive. 2. Internally by: • Eliminating small air spaces where corona could develop. • Making the space between conductors sufficiently long, so that a 2000 volt spike; cannot cause a partial discharge. • Advanced PWM control techniques are being developed to reduce the maximum spike voltage from 3 times to 2 times of DC voltage.

TR.39

Data subject to change without notice. 12/23 • www.wolongamerica.com