George Carlson's notes on RPC design (posted here) twice states a warning (IT CAN KILL YOU!) about not using safety ground for a reference for 115V control voltage. In the section titled "Simple Rotary Converter", the diagram is:
The warning that I'm referring to is contained in note 6 below the diagram.
The section on static phase converters has this diagram:
The second instance of his warning is in note 4 below this diagram. His workaround is in note 5.
I see that Fitch Williams also uses a transformer to obtain 115V control voltage. I assume it is for the same reason.
If safety ground is used for the control voltage reference, what situation could arise causing the operator to be killed?
The warning that I'm referring to is contained in note 6 below the diagram.
"6. In the drawing, the potential relay uses AC Neutral as a reference. DO NOT USE SAFETY GROUND INSTEAD OF AC NEUTRAL, IT CAN KILL YOU! Since rotary phase converters require a fixed installation, availability of AC Neutral should not be a problem. If it is, use the dual primary transformer trick shown in the section on static phase converters."
The section on static phase converters has this diagram:
The second instance of his warning is in note 4 below this diagram. His workaround is in note 5.
4. In the top drawing, the potential relay uses AC Neutral as a reference. DO NOT USE SAFETY GROUND INSTEAD OF AC NEUTRAL, IT CAN KILL YOU!
5. The bottom drawing uses a dual primary (120/240V) transformer to generate a reference. This is handy if the AC Neutral is not available. Any small transformer will work. EPO or Ace Electronics would probably have these. The voltage on the secondary is not important since it is not used.
5. The bottom drawing uses a dual primary (120/240V) transformer to generate a reference. This is handy if the AC Neutral is not available. Any small transformer will work. EPO or Ace Electronics would probably have these. The voltage on the secondary is not important since it is not used.
I see that Fitch Williams also uses a transformer to obtain 115V control voltage. I assume it is for the same reason.
If safety ground is used for the control voltage reference, what situation could arise causing the operator to be killed?