I used IRF840 MOSFET and i have three different grounds (300 V, 15 V, 5 V) in my circuit. Everything working fine, the MOSFET received gate signal correctly but when i connect a load coil there is no current flow in that. Tell me why this is happening

 

I used IRF840 MOSFET and i have three different grounds (300 V, 15 V, 5 V) in my circuit. Everything working fine, the MOSFET received gate signal correctly but when i connect a load coil there is no current flow in that. Tell me why this is happening

You need to show a circuit diagram.

 

Tell me why this is happening

Tell us how we can answer your question without seeing the circuit.

 

My crystal ball is hazy..... can't make out any details.

 

Three grounds at different, non-zero voltage is a misuse if the term. Ground is 0V by definition.

I suspect you have three power sources with different grounds, all of which are normally connected together. That is, if you want things to work.