The Case of the Frozen Drive


A Yaskawa 515 variable frequency drive at a local aerospace company wasn’t starting. The VFD had been working correctly until suddenly stalling in its tracks.


Upon arriving on the scene the CSI immediately recognized that the VFD run light was solid but the stop light was blinking. Thanks to his Yaskawa Authorized Service Provider training the CSI quickly recognized that on a Yaskawa VFD this indicates that the drive has no speed reference or zero speed reference. The potentiometer, which acts as a variable resistor to control the speed of the drive, was not set to zero.


When it was initially installed, the wire that connected the drive to the potentiometer was pulled too short. It wasn’t a problem for many years but wear and time had conspired to cause the wire to fall off.


The ACES CSI inserted a jumper between the wire and potentiometer to complete the circuit and the drive came back online, and stayed online. Since the CSI had special training with Yaskawa VFDs he was able to quickly analyze the problem, keeping this case study — and the client’s expenses — short and sweet.