A review of the reflected wave phenomenon was presented so that system users may understand the limitations of the new technology prior to VFD installation. Knowing motor cable length, VFD risetime and motor dielectric capability guarantees a successful installation by co-ordinating applied stress with motor dielectric withstand capability. Some VFD manufacturers have performed this coordination by giving maximum safe cable distances before external protection devices must be used and extended safe cable distances with external motor voltage protection added. Various solutions to the voltage stress problem were also given. The motor industry is rapidly improving its dielectric capability with new magnet wire and varnish so that the external solutions may only be temporarily needed over the next few years.
VFD keypad, operator control panel required for control, monitoring and measurements shall be supplied and installed outside the panel on the front door. VFD shall be accessible for operation without opening the front door and shall be non-removable type.
