Current monitor combining a shunt resistor with a Rogowski coil
A current measurement device with a shunt resistor of a resistive core with an opening and measurement leads, a Rogowski coil with electrical contacts surrounding the resistive core, conductive layers on first and second sides of the resistive core, one or more insulative layers between the conductive layers and the Rogowski coil, the current measurement device configured to combine signals from the shunt resistor and the Rogowski coil. The current measurement device may have a Rogowski coil on a flexible substrate at least partially wrapped around the shunt. A current measurement device has a rigid substrate, vias filled with a conductive material through the rigid substrate, conductive layers on the top surface and the bottom surface connecting to the vias to form a Rogowski coil structure, one or more insulative layers directly on the coil structure, a shunt resistor directly on the one or more insulative layers.
1 . A current measurement device, comprising:
a first measurement lead and a second measurement lead for electrically connecting the current measurement device to a test and measurement instrument or probe;
a shunt resistor, the shunt resistor comprising a resistive core having a first end, a second end opposite the first end, and an opening extending from the first end to the second end, the shunt resistor configured to be located in a current path of a current to be measured;
a Rogowski coil surrounding the resistive core, the Rogowski coil having electrical contacts;
a conductive layer on the first end of the resistive core, and a conductive layer on the second end of the resistive core; and
one or more insulative layers between each of the conductive layers and the Rogowski coil, the current measurement device configured to combine signals from the shunt resistor and the Rogowski coil.
2 . The current measurement device as claimed in claim 1 , wherein the current measurement device is configured to combine the signals by one of placing the Rogowski coil in series with the resistive core or adding the signals.
3 . The current measurement device as claimed in claim 1 , wherein the resistive core is electrically connected to one of the Rogowski coil electrical contacts and another of the Rogowski coil electrical contacts is electrically connected to the first measurement lead.
4 . The current measurement device as claimed in claim 3 , wherein the resistive core is electrically connected to one of the Rogowski coil electrical contacts through the conductive layer on the first end of the resistive core, and the conductive layer on the second end of the resistive core is connected to the second measurement lead.
5 . The current measurement device as claimed in claim 3 , wherein the resistive core is directly electrically connected to one of the Rogowski coil electrical contacts through a gap in the one or more insulative layers.
6 . The current measurement device as claimed in claim 1 , wherein one of the measurement leads is one of either electrically connected to the resistive core through the conductive layer on the second side of the resistive core, or directly electrically connected to the resistive core through a gap in the one or more insulative layers.
7 . The current measurement device as claimed in claim 1 , wherein the resistive core has a wall thickness selected to set a frequency at which the Rogowski coil becomes active.
8 . The current measurement device as claimed in claim 1 , wherein the Rogowski coil comprises a coil in a printed circuit board.
9 . The current measurement device as claimed in claim 1 :
wherein the Rogowski coil comprises a Rogowski coil on a flexible substrate at least partially wrapped around the resistive core.
10 . The current measurement device as claimed in claim 9 , wherein the Rogowski coil is configured so that no loop area exists in a dimension perpendicular to the Rogowski coil.
11 . The current measurement device as claimed in claim 9 , wherein the Rogowski coil comprises:
a first layer of the flexible substrate containing a first series of coil traces and first contact points;
a second layer of the flexible substrate containing a second series of coil traces and second contact points at least partially overlaying the first series of coil traces and first contact points in a z-direction; and
vias between the first layer and the second layer, the first series of coil traces and first contact points and the second series of coil traces and second contact points forming a Rogowski coil and one of the first contact points and the second contact points are connected to the shunt resistor.
12 . The current measurement device as claimed in claim 11 , further comprising a third layer between the first and second layers.
13 . The current measurement device as claimed in claim 12 , wherein the third layer contains a trace in a center of the Rogowski coil to act as a return path.
14 . The current measurement device as claimed in claim 12 , wherein the third layer is configured to provide mechanical stability to the flexible substrate, including being wider than other traces in the flexible substrate.
15 . The current measurement device as claimed in claim 11 , wherein the current measurement device is configured to produce a differential output signal.
16 . The current measurement device as claimed in claim 15 , wherein the first series of coil traces overlay the second series of coil traces so that the first contact points and the second contact points form an alternating A-B-A-B pattern in a y-direction dimension to locally cancel fields in the first dimension.
17 . The current measurement device as claimed in claim 15 , wherein the first series of coil traces overlay the second series of coil traces so that the first contact points and the second contact points form an A-B-B-A pattern centered in an x-direction and vary in a y-direction to locally cancel fields in the first dimension.
18 . The current measurement device as claimed in claim 15 , wherein the first series of coil traces overlay the second series of coil traces so that the first contact points and the second contact points form an A-B-B-A pattern centered in an x-direction and have opposing loops at extremes of the y-direction to cancel fields at a larger distance than locally canceling coils.
19 . The current measurement device as claimed in claim 9 , wherein the current measurement device is configured to produce a single-ended output signal.