ubern
Military
- Jun 29, 2008
- 4
I am trying to understand the reverse power relays to our steam driven generators. This is a discription of the device from the book:
"Potential signal flows through the top coil over a rotatable disc and transformer action induces a circulating current in the disc. Current signal flows through the bottom coil under the disc and produces magnetic flux that passes through the portion of the disc containing the circulating current. This causes motor action that rotate the disc" I can tell you from the drawing that the potential signal is taken across 2 phases of the potential transformer while the current signal is inline with a single phase of the current transformer. "A lag loop or shorted coil on the magnetic pole of the botom coil brings the lower pole flux in phase with thte upper pole flux at unity power factor reverse power flow conditions thereby creating maximum rotational forces. As the disc rotates, contacts mate and energize the reverse power relay"
Here is what i dont understand:
-If one of the two generators looses its prime mover then the other generator will maintain voltage, therefore the potential signal should not change.
-A difference in phases between voltage and current would be the same throughout the circuit so it cant be used to tell if real power is flowing into or out of a machine.
-Its an AC circuit so i know you cant say "current is flowing into or out of" the machine as it is always doing both equally.
- the only difference i can think of is that now there will be less current flow through the current transformer. But if this was the mechanism that activated the reverse power relay then the relay would be energized when the machine was unloaded.
What am i missing?...how is this circuit able to tell which direction real power is flowing?
Also, how does the lag loop bring pole fluxes in phase at unity power factor?
"Potential signal flows through the top coil over a rotatable disc and transformer action induces a circulating current in the disc. Current signal flows through the bottom coil under the disc and produces magnetic flux that passes through the portion of the disc containing the circulating current. This causes motor action that rotate the disc" I can tell you from the drawing that the potential signal is taken across 2 phases of the potential transformer while the current signal is inline with a single phase of the current transformer. "A lag loop or shorted coil on the magnetic pole of the botom coil brings the lower pole flux in phase with thte upper pole flux at unity power factor reverse power flow conditions thereby creating maximum rotational forces. As the disc rotates, contacts mate and energize the reverse power relay"
Here is what i dont understand:
-If one of the two generators looses its prime mover then the other generator will maintain voltage, therefore the potential signal should not change.
-A difference in phases between voltage and current would be the same throughout the circuit so it cant be used to tell if real power is flowing into or out of a machine.
-Its an AC circuit so i know you cant say "current is flowing into or out of" the machine as it is always doing both equally.
- the only difference i can think of is that now there will be less current flow through the current transformer. But if this was the mechanism that activated the reverse power relay then the relay would be energized when the machine was unloaded.
What am i missing?...how is this circuit able to tell which direction real power is flowing?
Also, how does the lag loop bring pole fluxes in phase at unity power factor?