Rockwell Automation 1336T Wiring and Grounding Guide, (PWM) AC Drives - Manual (Page 80)

80 Rockwell Automation Publication DRIVES-IN001M-EN-P - March 2014
Chapter 6 Electromagnetic Interference
Enclosure Lighting Fluorescent lamps are also sources of EMI. If you must use fluorescent lamps
inside an enclosure, follow these precautions to help guard against EMI
problems:
• Install a shielding grid over the lamp
• Use shielded cable between the lamp and its switch
• Use a metal-encased switch
• Install a filter between the switch and the power line, or shield the power
line cable
Bearing Current The application of pulse-width modulated (PWM) inverters has led to
significant advantages in terms of the performance, size, and efficiency of variable
speed motor controls. However, the high switching rates used to obtain these
advantages can also contribute to motor bearing damage due to bearing currents
and electric discharge machining (EDM). Bearing damage on motors supplied by
PWM inverters is more likely to occur in applications where the coupling
between the motor and load is not electrically conductive (such as belted loads),
when the motor is lightly loaded, or when the motor is in an environment with
ionized air. Other factors, such as the type of grease and the type of bearings used,
can also affect the longevity of motor bearings. Motor manufacturers that design
and manufacture motors for use with variable frequency drives can offer solutions
to help mitigate these potential problems.
Shielding Grid
Over Lamp
Shielded
Cable
Metal-encased
Switch
Filter AC Power
Line Filter or
Shielded Power
Line