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EV.5.8 Tractive System Measuring Points - TSMP
EV.5.8.1 Two Tractive System Measuring Points (TSMP) must be installed in the vehicle which are:
a. Connected to the positive and negative motor controller/inverter supply lines
b. Next to the Master Switches EV.7.9
c. Protected by a nonconductive housing that can be opened without tools
d. Protected from being touched with bare hands / fingers once the housing is opened
The Tractive System Measuring Points (TSMP's) are used to ensure that High Voltage measurements within the Tractive System can be taken in a controlled and safe manner during inspection, maintenance, and testing phases. EV.5.8.1.a requires that two TSMP's are connected to opposite poles of the inverter supply lines, which allows for monitoring and testing of the live, supplied voltage. Additionally, EV.5.8.1.b requires that these measuring points be next to the Tractive System Master Switch (TSMS) and Grounded Low Voltage Master Switch (GLVMS) described in EV.7.9.
Shown to the right is our Master Schematic, and within the Right Panel Enclosure, you can see that the TSMS and GLVMS are both in close proximity to the two TSMP's.
Schematic - Right Panel
Schematic - Right Panel
Rules Reference - EV.7.9
Rules Reference - EV.7.9
EV.7.9 Master Switches
EV.7.9.1 Each vehicle must have two Master Switches that must:
a. Meet T.9.3 for Configuration and Location
b. Be direct acting, not act through a relay or logic
EV.7.9.2 The Grounded Low Voltage Master Switch (GLVMS) must:
a. Completely stop all power to the GLV System EV.4.4
b. Be in the center of a completely red circular area of > 50 mm in diameter
c. Be labeled “LV”
EV.7.9.3 The Tractive System Master Switch (TSMS) must:
a. Open the Shutdown Circuit in the OFF position EV.7.2.2
b. Be the last switch before the AIRs except for Precharge circuitry and Interlocks.
c. Be in the center of a completely orange circular area of > 50 mm in diameter
d. Be labeled “TS” and the symbol specified in ISO 7010-W012 (triangle with black lightning bolt on yellow background).
e. Be fitted with a "lockout/tagout" capability in the OFF position EV.11.3.1
In rule EV.7.9.1, we are prompted to look at a Technical Aspects rule (T.9.3) which address points related to the Master Switch's configuration and location. Standardization of those two categories ensures the safety of drivers, spectators, and operators alike. This rule also requires that the switch act directly, so as not to incur delay through using relays or logic boards.
EV.7.9.2 and EV.7.9.3 both offer insight on the Grounded Low Voltage Master Switch (GLVMS) and Tractive System Master Switch (TSMS), respectively. In the case of the GLVMS, actuating the master switch must cut all power to the Low Voltage system of our car. It should conform to a color, shape, and size standard as well as be properly labeled so that it is easy for an untrained eye to identify.
For the TSMS, it must open the Shutdown Circuit when actuated, and, excluding precharge circuits and interlocks, must be connected just before the Accumulator Isolation Relays (AIR's). This switch must also be properly labeled, colored, sized, and shaped to conform to the standards set by this rule and make it easy to identify. Finally, this switch must be lockable in the 'OFF' position so that teams are able to work on the vehicle safely.
Rules Reference - T.9.3 (Referenced in EV.7.9)
Rules Reference - T.9.3 (Referenced in EV.7.9)
T.9.3 Master Switches
Each Master Switch ( IC.9.3 / EV.7.9 ) must meet the following:
T.9.3.1 Location
a. On the driver’s right hand side of the vehicle
b. In proximity to the Main Hoop
c. At the driver's shoulder height
d. Able to be easily actuated from outside the vehicle
T.9.3.2 Characteristics
a. Be of the rotary mechanical type
b. Be rigidly mounted to the vehicle and must not be removed during maintenance
c. Mounted where the rotary axis of the key is near horizontal and across the vehicle
d. The ON position must be in the horizontal position and must be marked accordingly
e. The OFF position must be clearly marked
f. (EV Only) Operated with a red removable key that must only be removable in the electrically open position
Rules Reference - EV.4.4 (Referenced in EV.7.9)
Rules Reference - EV.4.4 (Referenced in EV.7.9)
EV.4.4 Grounded Low Voltage System
EV.4.4.1 The GLV System must be:
a. A Low Voltage system that is Grounded to the Chassis
b. Able to operate with Accumulator removed from the vehicle
EV.4.4.2 The GLV System must include a Master Switch, see EV.7.9.1
EV.4.4.3 A GLV Measuring Point (GLVMP) must be installed which is:
a. Connected to GLV System Ground
b. Next to the TSMP EV.5.8
c. 4 mm shrouded banana jack
d. Color: Black
e. Marked “GND”
EV.4.4.4 Low Voltage Batteries must meet T.9.2
Rules Reference - EV.7.2.2 (Referenced in EV.7.9)
Rules Reference - EV.7.2.2 (Referenced in EV.7.9)
EV.7.2.2 When the Shutdown Circuit Opens:
a. The Tractive System must Shutdown
b. All Accumulator current flow must stop immediately EV.5.4.3
c. The voltage in the Tractive System must be Low Voltage T.9.1.2 in five seconds or less
d. The Motor(s) must spin free. Torque must not be applied to the Motor(s)
Rules Reference - EV.11.3.1 (Referenced in EV.7.9)
Rules Reference - EV.11.3.1 (Referenced in EV.7.9)
EV.11.3 Lockout
EV.11.3.1 The TSMS EV.7.9.3 must be locked in the OFF position when any work is done on the vehicle.
Photo - Vehicle TSMP's
Photo - Vehicle TSMP's
EV.5.8.1.c requires that the TSMP's be protected by a nonconductive housing to prevent accidental contact with live electrical components, reducing the risk of electric shock or short circuits. The measuring points must also be accessible within the housing and without having to use tools, and this because we want to reduce the time it would take to fix a high-voltage electrical issue at the measuring point in case of emergency. As for EV.5.8.1.d, this rule requires that people are protected from inadvertent contact under normal operation, and that the measuring points are finger/hand safe when the enclosure is opened. As shown to the left, our configuration in 2023 had properly insulated connections that did just that!
EV.5.8.2 Two TSMPs must be installed in the Charger EV.8.2 which are:
a. Connected to the positive and negative Charger output lines
b. Available during charging of any Accumulator(s)
Rules Reference - EV.8.2
Rules Reference - EV.8.2
EV.8.2 Charger Features
EV.8.2.1 The Charger must be galvanically isolated (AC) input to (DC) output.
EV.8.2.2 If the Charger housing is conductive it must be connected to the earth ground of the AC input.
EV.8.2.3 All connections of the Charger(s) must be isolated and covered.
EV.8.2.4 The Charger connector(s) must incorporate a feature to let the connector become live only when correctly connected to the Accumulator.
EV.8.2.5 High Voltage charging leads must be orange
EV.8.2.6 The Charger must have two TSMPs installed, see EV.5.8.2
EV.8.2.7 The Charger must include a Charger Shutdown Button which is:
a. A push-pull or push-rotate emergency switch
b. Minimum diameter of 25 mm
c. Labelled with the international electrical symbol (a red spark on a white edged blue triangle)
This rule requires that, in addition to the aforementioned TSMP's found in the vehicle, teams have another two TSMP's in their Accumulator Charger/Charging Cart.
As shown in the picture to the right, our 2023 vehicle iteration had two TSMP's installed in the Accumulator Charger (I am holding the two measuring points, and the nest of cables behind my hand is the Accumulator Charger). Specifications for this Charger can be found in EV.8.2, but a synopsis is as follows:
Photo - Charging TSMP's
Photo - Charging TSMP's
EV.8.2.1 requires that the alternating current (AC) input must be separated to prevent direct current flow to the (DC) output, while still allowing for signal transmission. The difference between these two types of current is that AC current periodically reverses direction, whereas DC current flows steadily in one direction. In EV.8.2.2, it is made clear that a conductive charger housing must be connected to the earth ground of the AC input, and this is necessary in the event of a fault where the conductive housing becomes live (due to internal wiring issues or external damage), to ensure that that excess current flows safely to the ground of the external system.
The red Ground (GND) slot shown on the right is our connection to AC Earth GND.
Photo - AC Earth GND
Photo - AC Earth GND
EV.8.2.3 and EV.8.2.4 requires that the Charger connections must be in a safety connector or properly boxed, as well as have an electrical interlock on the charger connector. By using an interlock, the circuit will be broken if the connectors are not correctly aligned. EV.8.2.5 designates the charging leads as High Voltage (HV), and states that these must be colored orange to conform with our other High Voltage cable specifications. In EV.8.2.6, we establish that the Charger needs two TSMP's (and for the sake of redundancy, this is already stated in EV.5.8.2). Finally, EV.8.2.7 provides type, size, and labeling specifications for a Charger Shutdown Button which allow for it to be easily identified to even an untrained eye.
Back to the original rule, though, EV.5.8.2.a requires that the TSMP's have to be connected to opposite poles of the Charger's output lines, and according to EV.5.8.2.b, charging of the Accumulator(s) should not interfere with the accessibility of these measuring points.
EV.5.8.3 The TSMPs must be:
a. 4 mm shrouded banana jacks rated to an appropriate voltage level
b. Color: Red
c. Marked “HV+” and “HV-“
Photo - Vehicle TSMP's
Photo - Vehicle TSMP's
Even though the shielding is orange, the banana jacks themselves are still red!
Shown on both the right and left, our TSMP's for the 2023 vehicle were in compliance with the color, labeling, and component requirements specified by this rule group.
Both of these TSMP sets have separate rules specific to the configuration of each, but still conform to the set of base rules defined in EV.5.8.3.
Photo - Charging TSMP's
Photo - Charging TSMP's
The HV+ and HV- markings are done with heat-shrinked labels, and in this picture, obstructed from view.
EV.5.8.4 Each TSMP must be secured with a current limiting resistor.
a. The resistor must be sized per the following:
Maximum TS Voltage (Vmax) Resistor Value
Vmax <= 200 V DC 5 kOhm
200 V DC < Vmax <= 400 V DC 10 kOhm
400 V DC < Vmax <= 600 V DC 15 kOhm
b. Resistor continuous power rating must be more than the power dissipated across the TSMPs if they are shorted together
c. Direct measurement of the value of the resistor must be possible during Electrical Technical Inspection.
Current limiting resistors are chosen based on Ohm's Law (V = IR), where V is the voltage drop across the resistor, I is the current flowing through it, and R is the resistance value. By selecting an appropriate resistance value, the resistor limits the amount of current that can flow through the circuit. Naturally, a higher Tractive Voltage rating would equate to the need for a higher Resistor Value needed to offset the surplus. This is why EV.5.8.4.a utilizes a table with a range of resistances dependent on Maximum Tractive Voltage, where as the voltage increases, the resistance required also increases proportionally.
As for EV.5.8.4.b, this rule expects teams to prepare for a fail-case where the TSMP's are shorted together. In this case, the resistors connected to them will dissipate power as heat, and if the resistor's power rating is insufficient, it may overheat, potentially leading to its failure or even causing damage to nearby components. Because of this, the rule requires that the resistor chosen must have a continuous power rating higher than the maximum power dissipated during a short circuit. The resistor's minimum power dissipation requirement can be calculated as P = (V x V) / R or P = (I x I x R) where V is voltage, I is current, and R is resistance.
Finally, EV.5.8.4.c just says that the resistor should be accessible during Electrical Technical Inspection to be properly measured.
EV.5.8.5 Any TSMP must not contain additional Overcurrent Protection.
Overcurrent protection devices, such as fuses or circuit breakers, are typically integrated into the main power distribution and protection scheme of the vehicle. TSMP's are intended for diagnostic and measurement purposes, so not only are they usually distinct from the main power distribution path, adding additional overcurrent protection could interfere with the accurate measurement of voltages. Fusing, for example, may blow and give the TSMP's a false 0V reading.
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