با رجوع به IEEE 1050 دلایل متعددی برای تداخلات سیگنالی روی تجهیزات ابزار دقیق الکتروموتورها به شرح زیر می توان یافت که از نقطه نظر تداخلات اطلاعاتی حائز اهمیت است.
Electro-mechanical equipment and some forms of rotating equipment, such as that containing unshielded windings or fields, centrifugal switches, armature brushes, or slip-rings, contain many possible internal sources of high-frequency interference. These include:
a) Partial (corona) discharges within the stator winding insulation of motors. Note that this can also occur on dry-type transformers.
b) Slot discharges between coil surfaces and the stator iron.
c) Sparking from exciters with brushes.
d) Arcing associated with conductor strands that have fractured from copper fatigue. This arcing is not continuous but is caused by a movement of conductor surfaces as a result of steady-state and transient magnetic forces.
e) DC machine brushes.
f) Centrifugal switch contact operation and arcing.
g) Older types of non metal-enclosed or other inadequately shielded motor-controllers with arcing contacts.
These may be of the manual or contactor type. Non-interlocked, manually operated reversing and motor “plugging” types of controls are potential problem sources since they may be operated while the motor is still spinning.
h) Variable frequency or pulse inverter drives. These are also capable of producing both conductive and radiated EMI from the fast transition times associated with SCR, IGBT, or similar motor inverter-driver switching schemes. The largest number of conducted EMI problems involving this type of equipment occur in the range of the first 100 harmonics of the fundamental frequency of the driver circuit.
i) Distributed capacitance. A motor that is being initially energized or in some cases de-energized is capable of coupling a transient current from its winding to its metal frame/enclosure and thence into the associated equipment grounding system for that motor. The coupling mechanism, in this case, is the distributed capacitance from the winding to the case and is proportional to motor size and voltage rating. Large motors operating at medium voltage can produce the greatest EMI effects, particularly since these typically have a large number of associated I&C circuits.
با اینحال یکی از عوامل شایع در سوختن تجهیزات ابزاردقیق وقوع اضافه ولتاژهای مخرب خازنی ناشی از تفکیک زمین برق و ابزار دقیق می باشد که برای چزئیات بیشتر می توانید به IEEE 142 مراجعه فرمائید.