RTD Induction Voltage for 11KV Synchronous Motors

Imstrument cables & power cables should be run seperatly from each other ....

The shield should be connected at one end only.

instruments cables and power cables are leid separatly with distance of 600 mm

the shield are connected at one end only

When you wind a electrical motor and places RTD's inside this winding, it is important that the start and return pad of the RTD are in the same direction.

Do not make a circular pad with het RTD connection leads.

If you used a high impedance meter to measure this 145V, it might be only low energy coupling that will be negligible once connected to the low impedance input.

Connect a 1K resistor to ground (or a small light bulb) and measure it again. At these voltages, a few pF of capacitance can generate many volts in a 1Mohms meter.

Bingo, GA.

I often see people assuming they are seeing "real" voltages when in fact they only see it with a very high impedance digital multimeter. Using an older analog meter movement (D'Arsonval) which places a burden on the circuit will make that reading go away. The question then is, how does the PLC input read it? If you are using a specific RTD input module it probably takes that into design consideration, that's why you don't want to use a standard analog voltage input module for RTDs. If you don't have an RTD input module, or the one you have has high impedance (why it would I don't know), then you may need that resistor mentioned by marcot even in your PLC circuit.

Thanks JRaef,

To read a RTD, the plc has to supply a current from a relatively low impedance source. The RTD usually has 100 ohms. While the analog input will have a high impedance, the source that supplied the reading current will have a relatively low impedance. This should bring the RTD voltage close to "ground".

If the coupling is only a few pF, everything should be fine when connecting to the PLC. BUT I would test first with a resistor load or the like as if it is a short to a coil, the result could be dangerous.