8
The high voltage power circuits are fully isolated from the logic control and CAN circuits. All of the required
power supplies and control signals for the high voltage system are isolated from the low voltage system.
All the control inputs and outputs such as the analogue inputs, digital inputs and motor encoder are referenced to the
12/24V logic circuit ground. The CANbus is connected to the control circuit ground.
Do not connect the high voltage circuit to the 12/24V logic circuits directly. If you do this the isolation
barrier will be bypassed. This could cause high voltages to be present on circuits which do not have
enough protection against accidental touch.
Power conversion section
The power conversion section of Dragon8 employs a 6-switch MOSFET bridge. Excellent electrical and
thermal efficiency is achieved by:
• Minimization of thermal resistances.
• Use of the latest MOSFET technology
• Internal thermal protection (if temperatures are excessive, switching frequency and output torque
may be reduced).
• Overcurrent protection using device characteristics.
• Internal measurement of output current.
• Overvoltage trip in the event of regenerative braking raising battery voltage to unsafe levels.
Interfaces
In addition to its motor control functions, Dragon8 offers many other functions designed to interface
with electric systems. A variety of digital and analog input sources are supported.
On/off control of contactors is provided by Dragon8. All I/O on the Dragon8 controller is protected
against short-circuit to the control logic positive and negative logic supply.
Dragon8 connectivity and interoperability with other system devices (for example A VCU) using a
CANbus, the CANopen protocol, Sevcon’s H-protocol (providing J1939 compatibility) and Sevcon’s I-
protocol is provided. In addition to in-service operation, the CANopen protocol allows the controller to
be commissioned using the Sevcon DVT tool.
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