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BSPD current sensor

The BSPD is a part of the shutdown circuit. Its job is to detect when there is simultaneous braking and high power output. This means that the driver could be accelerating and braking at the same time and it will trip the shutdown circuit, switching off the car. As a important safety aspect in the shutdown circuit it needs to be tested to prove that the system works. The method to detect the power output is through a hall effect current sensor, measuring the current that is passing through. To test this without driving is difficult and this check procedure occurs before driving is allowed. This means a solution needs to be developed to simulate the current going through when needed for tech inspection.


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

The current sensor measures current passing through, however the rules dictates for a power draw of 5kW. This means to simulate the power of 5kW a certain amount of current needs to pass through. 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, in the 10 amps range which isn't 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. 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
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