System and method for e-machine stator insulation resistance monitoring

A system for monitoring an insulation resistance (IR) of an e-machine, the system comprising:

• a bridge circuit arrangement with a power source, a first arm electrically connected to the e-machine and having an unknown first resistance (R1) corresponding to the IR of the e-machine, a second arm having a second resistance (R2), a third arm with a predetermined third resistance (R3), and a fourth arm with a predetermined fourth resistance (R4), the first arm and the second arm being electrically connected at a first node (X) to collectively define a first side of the bridge circuit arrangement, and the third arm and the fourth arm being electrically connected at a second node (Y) to collectively define a second side of the bridge circuit arrangement, the bridge circuit arrangement including a bridge that is electrically connected to the first node and the second node to operatively connect the first side and the second side of the bridge circuit arrangement, the bridge including a sensor configured to detect a voltage Vxy between the first node and the second node;
• a control system that is operatively connected to the bridge circuit, the control system including a processor;
• the processor configured to detect the voltage Vxy;
• the processor configured to calculate IR as the first resistance (R1) associated with the detected voltage Vxy.

A method of monitoring an insulation resistance (IR) of an e-machine with an electrical insulator, the method comprising:

• providing a bridge circuit arrangement with a power source, a first arm electrically connected to the e-machine and having an unknown first resistance (R1) corresponding to the IR of the electrical insulator, a second arm having a variable second resistance (R2), a third arm with a known third resistance (R3), and a fourth arm with a known fourth resistance (R4), the first arm and the second arm being electrically connected at a first node (X) to collectively define a first side of the bridge circuit arrangement, and the third arm and the fourth arm being electrically connected at a second node (Y) to collectively define a second side of the bridge circuit arrangement, the bridge circuit arrangement including a bridge that is electrically connected to the first node and the second node to operatively connect the first side and the second side of the bridge circuit arrangement, the bridge including a sensor configured to detect a voltage between the first node and the second node;
• providing a control system that is operatively connected to the bridge circuit, the control system including a processor;
• selectively adjusting, by the processor, the second resistance (R2) to a selectively adjusted value in which the sensor detects the voltage to be approximately zero to balance the first side and the second side of the bridge circuit arrangement;
• calculating IR, by the processor, as a product of the selectively adjusted value of the second resistance (R2) and the third resistance (R3), divided by the fourth resistance (R4) (IR=R1=(R2*R3)/R4);
• determining, by the processor, if the calculated IR is below a predetermined threshold;
• and
• outputting an user output as a result of the processor determining that the IR is below the predetermined threshold.