Hi Everone, i have a small lathe i've been using for the past 10 years or so and never noticed todays problem before, today I got a small electric shock when i touched the bed of the lathe and a scaffold pole I have situated next to the lathe which holds up a scaffold lean-to roof.
After this shock I tested using a wooden handled lathe tool to short the pole to the lathe bed which resulted in small sparking (almost like running a 12v wire onto earth in car).
The lathe 3 phase motor runs from a vfd single to 3 phase inverter, I checked the earths etc and connections in the motor along with the connections from inverter to motor as well as the inverter 240v feed, no problems were detected, I even tried disconnecting the earth connections but same problem.
I tested using a multi-meter set on (ac voltage 250v) from the lathe bed to the pole and it reads around 130v, also from motor casing to the pole same reading.
Thinking it may be a problem with the motor i wired a new motor using the existing motor connections and the reading from new motor case to pole was still 130v.
I then tried a spare vfd on the new motor and low a behold when running i get a voltage reading from the motor case to the pole of 130v??
Anyone any idea why this may be happening as I say I've run the lathe for 10 years or more and never noticed any problem, any help appreciated thanks.
By the way the voltage readings are only present when the inverter is switched on.
Help appreciated, Jeff
After this shock I tested using a wooden handled lathe tool to short the pole to the lathe bed which resulted in small sparking (almost like running a 12v wire onto earth in car).
The lathe 3 phase motor runs from a vfd single to 3 phase inverter, I checked the earths etc and connections in the motor along with the connections from inverter to motor as well as the inverter 240v feed, no problems were detected, I even tried disconnecting the earth connections but same problem.
I tested using a multi-meter set on (ac voltage 250v) from the lathe bed to the pole and it reads around 130v, also from motor casing to the pole same reading.
Thinking it may be a problem with the motor i wired a new motor using the existing motor connections and the reading from new motor case to pole was still 130v.
I then tried a spare vfd on the new motor and low a behold when running i get a voltage reading from the motor case to the pole of 130v??
Anyone any idea why this may be happening as I say I've run the lathe for 10 years or more and never noticed any problem, any help appreciated thanks.
By the way the voltage readings are only present when the inverter is switched on.
Help appreciated, Jeff