Embedded Files
Description
Description
The goal of the REV2 Pre-Charge system is to protect the motor controller from the in-rush current during the initial ignition of the bike. With a sudden large difference in voltage coming from the battery pack to the motor controller the risk of this in-rush current causing heating issues becomes a main concern. The Pre-Charge on its most basic level acts as a large resistor to restrict the amount of in-rush current to the motor controller to reduce high voltage power from entering, which then charges the internal capacitors of the motor controller. These charged capacitors lessen the energy difference between the battery pack and motor controller, which reduces the chance of inrush current.
This system makes use of two separate circuits; a 12V low voltage control circuit, and a 400V high voltage main power control. Once an ignition signal is received the Pre-Charge system begins receiving the 400V high voltage from the battery pack, eventually the motor controller will send a signal to the pre-charge to begin entering the 12V low voltage control-circuit. The low voltage circuit is responsible for controlling the timing of signals coming from the REV2 handlebar. The high voltage power side is controlled by one signal coming from the motor controller, which is dependent on the low voltage side working as intended. In addition to this functionality the Pre-Charge system also receives inputs from other devices and outputs them to their corresponding systems.
Features
Features
Overvoltage Protection
Overvoltage Protection
Once ignition of the bike has been started 400V is applied to the Pre-Charge, to ensure the safe transfer of current to the motor controller the Pre-Charge applies a resistance large enough to lower the current to a safe value and ensure the instantaneous power is never too high for the motor controller to operate.
This current then charges the internal capacitors of the motor controller to further ensure that the energy difference between them and the battery pack is similar to reduce the chance of in-rush current.
12V Power Supply
12V Power Supply
Once the PRECHRG_DONE signal from the motor controller is received as a high value the Pre-Charge (In reality a low signal, but input is inverted) will shift functionality to a 12V power supply to the motor controller. This 12V low voltage control circuit manages the timing of signals coming from the REV2 handlebar.
Signal Relaying
Signal Relaying
High Voltage Signal Relay
HV_IN - The High Voltage input to the Pre-Charge system is connected to the 400V supplied by the battery pack.
HV_OUT - The High Voltage output of the Pre-Charge system is connected to the DC+ of the motor controller.
It is important to note that these are not direct connections of the 400V directly to the DC+ input of the motor controller, as shown in the block diagram a resistor resides between these two signals. This resistor has inputs:
R1_IN1 - First input to the screw-terminal connector (J?) which acts as a bidirectional relay of current with the value of the BAT+ (400V), this screw terminal then acts as an input to the power resistor.
R1_IN2 - Second input to the screw terminal connector (J?) which acts as a bidirectional relay of current to and from the DC+ of the motor controller, screw terminal then acts as an input to the power resistor.
Important to note that the screw terminal enables this bidirectional current movement.
Low Voltage Signal Relay
12V_IN - The Low Voltage Input to the low voltage power supply part of the pre-charge board, connected to a 12V power source.
MC_12V - Gives 12V to something (J2-21, J2-15)
PRECHRG_DONE - Inverted signal that is sent from the motor controller to the pre-charge board that begins sending 12V to the motor controller. This causes a current which activates a relay switch to enable the 12V to be supplied to the motor controller. Additionally the current activates an LED to verify the pre-charge has been finished. The 12V provided to the motor controller goes to pins J2-8 and J2-23.
Handlebar Signal Relay
IGN - Represents the ignition signal that is sent from the handlebars to the motor controller, has pin J1-9 determines when the KEY-SWITCH, has been activated. Connected to a diode in the pre-charge board to supply "12V" to the motor controller before pre-charge has completed. Once pre-charge is complete the diode prevents current going into the ignition key switch.
START - Represents the START signal that is sent from the handlebars to the motor controller, has pin J1-21 determines when the start button has been pressed.
J1-9 - Pin routed to the motor controller.
J1-21 - Pin routed to the motor controller.
Motorcontroller Signal Relay
Motor Controller receives 4 inputs from the pre-charge board;
J1-9 - Determines when the KEY-SWITCH has been activated.
J1-21 - Determines when the START signal has been activated.
J2-8 - 12V output from the low voltage control circuit.
J2-23 - 12V output from the low voltage control circuit.
Figure 1:
Figure 1 shows the block diagram for the systems which pre-charge the high voltage signal and sends it to the motor controller.
Figure 2:
Figure 2 shows the block diagram for the low voltage portions of the board which handle the input signals, 12V power for the motor controller, and the status LED.
Figure 3:
Figure 3 shows the block diagram for the mounting holes. These allow screws to go through the board and attach it to the mechanical components.
The main goal of the pre-charge board is to ensure the safe functioning of the REV2 bike and to protect it from in-rush current during the initial start-up of the bike. As can be seen in Figures 1 and 2, to accomplish this task two signals must be sent to the motor controller. Once the IGN signal has been received the motor controller then sends a signal to pin J2-21 which indicates that the Pre-Charge system can begin. Additionally, the ignition key switch sends a "12V" signal to the motor controller before the pre-charge has completed. Once current begins to flow through J2-21 it activates a relay which completes another part of the pre-charge circuit so that current can now flow through a large resistor labelled R_IN1 and R_IN2. The current that flows from the 400V battery through the resistor to the motor controller that then begins to charge the internal capacitors of the motor controller. By charging the internal capacitors of the motor controller the voltage inside the motor controller matches the battery which then decreases the chance of in-rush current causing an issue. Once the internal capacitors have fully charged the motor controller then sends a signal back to the pre-charge board through the port J2-15, or the pre-charge done signal. Once this signal is received high, (technically a low signal because the input is inverted) current begins to flow through the 12V control circuit. To ensure that once pre-charge has completed that current from the 12V LVSS does not flow back to the ignition switch a diode is present to prevent such an issue. Once current begins to flow through the 12V control circuit an indicator LED lights up to show that the pre-charge has completed, and in addition causes a relay to be activated which completes the circuit allowing 12V to be supplied to the ports J2-8, and J2-23 of the motor controller.
Physical Constraints
Physical Constraints
The board is placed on the bottom of the HVPH top plate. It must fit next to the GFD board and have space for the connectors to be plugged in without interfering with the other boards.
Component Selection
Component Selection
The most difficult component to select was the power resistor. We determined the size by examining the time requirement for precharging the motor controller and the maximum instantaneous power.
PreCharge time: 3τ less than one second → 3 x R x C < 1T → R < T/3C = 1 second / 3x500E-6 Farad = 666.667Ω
If precharge does not complete in one second, the motor controller thinks an error has occurred
Power Rating: PMax < V2/R = (400 V)2/R → R < (400 V)2/PMax
Power Tree
Power Tree
PCB Images
PCB Images
3D MODEL
3D MODEL
Design Review Power Point
Not necessarily up-to-date information
Roadmap
Roadmap
Team Norms
Team Norms
All team members are expected to participate 2-3 times a week. This equates to approximately 8 hours a week. When this is the case there are no individuals on the team but a team. When one member of the team makes a mistake the whole team gets credit for the mistake. When one member of a team does something well the whole team gets credit for doing it well. It is not a competition within your project team. The project lead is responsible for the project and is expected to speak for and accept responsibility for the team.
Project Team Members
Project Team Members
Team Lead> - Zachary Trager Macdonald - 413-461-0192
Team Member - Adam Lebouitz
Team Member - Austin Smith
Team Member - Kiernan O'Neil
Team Member - Nicholaos Banakos
Team Member - Tevin Hendess
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