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BSPD current sensor

The BSPD is an integral component of the shutdown circuit. Its function is to detect situations where braking and high power usage occur simultaneously. In other words, if the driver is accelerating and braking at the same time, the BSPD will trigger the shutdown circuit, turning off the vehicle. As a critical safety feature, it is essential to test the BSPD to ensure that the system functions correctly.

The system detects power output using a Hall effect current sensor, which measures the current passing through the wire it surrounds.

During the technical inspection, it is necessary to verify that this part of the shutdown circuit operates as intended. However, testing requires the current sensor to measure actual current flow. This can be done by jacking up the car and spinning the wheels in the air and pressing the brakes, however this may not be feasible. Therefore, a solution must be developed to simulate current passing through the sensor for testing purposes.

image.pngA hall effect current sensor

The BSPD must Open the Shutdown Circuit EV.7.2.2 when the two of these exist:
• Demand for Hard Braking EV.4.6
• Tractive System current is at a level where 5 kW of electrical power in the DC circuit is delivered to the Motor(s) at the nominal battery voltage

  • EV.7.7.2

This project will focus on the TS power level, where the BSPD check is already handled by the SCUM.

Implementation

The current sensor measures current passing through and is independent of the voltage, however the rules dictates for a power draw of 5kW. Power is comprised of current and the voltage. This means to simulate the power of 5kW through the tractive system, a certain amount of current will pass through the current sensor.

To calculate the current for 5kW, we can P=IV. Where V is the nominal TS voltage. This is the current that needs to pass through the current sensor. However this value is usually fairly high, for example 10 amps range which isn't always feasible to pass through the current sensor. However there is a solution to this, by wrapping wire around the current sensor multiple times, the current sensor will be able to detect the current passing through as increasing. eg. 1 amp looped 10 times will measure 10 amps.

To supply the current the GLV power system will be used. So to calculate the value of the resistor required we need to use V=IR. Where V is the nominal voltage of the GLV power system (12v). It is possible to pass 10 amps through another wire but consider the practical aspect of drawing so much current through the GLV battery and wire. The main decisions that you will need to make is the resistor value and the number of turns around the current sensor. 

Important considerations in component selection:

  • Power rating/ current rating of switches and wires
  • Size of components
  • Easy of maintenance and verification
  • Size/ packaging

Bonus points:

  • A good write up on how you designed it
  • Write a python program to do all the calculations. 
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