Electric Hybrid Propulsion

The Mega-Guard Electric and Hybrid Propulsion system is a complete electric motor propulsion system


The Mega-Guard Electric and Hybrid Propulsion system is a complete electric motor propulsion system. The Mega-Guard EHP can be integrated in ships with an AC switchboard or it can be integrated in DC Bus based ships where the AC switchboard is omitted. The DC Bus makes full use of the capabilities of electric propulsion and is more efficient and economic as well. This brochure describes the application of Mega-Guard Electric and Hybrid Propulsion solution based upon DC Bus.


The Mega-Guard EHP consists of the following main components:

  • Electric Torque Motor supporting direct shaft drive (low RPM) and gearbox shaft drive (medium RPM) applications in the range of 50KW to 2MW
  • High Power Inverter with the following selectable functions:
    • Electric Torque Motor control with Variable Frequency Drive (HPI-VFD)
    • Generator control with Active Front End for DC and AC generation (HPI-AFE)
    • Battery charging and discharging with the two way DC-DC conversion (HPI-DCDC)
    • AC Grid providing power for the AC auxiliaries and capability to receive power from shore connection (HPI-ACG)
  • Battery Bank built-up with lightweight 52VDC Battery Modules in series and including BMS
  • Propulsion Control System

Propulsion Control System

The Mega-Guard Propulsion Control System (PCS) fully automates the remote control on the bridge of the electric propulsion motor and in case of hybrid configurations, the diesel propulsion motor. Mega-Guard PCS gives control commands to the electric power generating plant as well (diesel generator or battery bank) and makes sure that no overloading condition will occur. Hybrid configurations with automatic change over from electric propulsion motor to diesel propulsion motor, when e.g. more ship's speed is required, is fully supported by Mega-Guard PCS. A boost mode can also be selected where both the electric propulsion motor and the diesel propulsion motor power the ship. The Mega-Guard PCS includes on bridge a speed setting lever and an 8.4” or 5.7” TFT for operator mode selection and display of the complete propulsion and generating plant.

Electric Torque Motor

The Mega-Guard Electric Torque Motors are all semi-custom built and are available in low to medium RPM versions; starting from 225 RPM up to 3000RPM with voltages ranging from
400 to 690VAC. The Electric Torque Motors are built-up with permanent magnets which reach efficiencies up to 96%. The low RPM Electric Torque Motor makes it possible to have a direct connection to the shaft without using gearboxes. In addition, hybrid configurations are supported where the Electric Torque Motor is mounted along the shaft of the diesel propulsion engine. The trade-off which has to be made with low RPM motors is regarding size and weight; the lower the RPM the bigger and heavier the Electric Torque Motor and the cost increases as well.  However, applying a low RPM Electric Torque Motor results in the highest efficiency and weight elimination of a heavy gearbox. The Electric Torque Motors are standard available in power ranges from 50KW up to 2MW. The Mega-Guard EHP also supports electric motors from other suppliers.

DC Bus

The Mega-Guard EHP system fully supports DC Bus technologies which has the following advantages:

  • eliminating  traditional AC switchboard
  • diesel generator can run at variable RPM in optimum mode in order to safe fuel
  • less electrical losses through less conversions from AC to DC and back to AC
  • less components needed to connect shore power to DC Bus
  • weight saving through less components
  • environmental friendly as less carbon gasses are produced

AC auxiliaries which can´t run on the DC Bus are fed through a High Power Inverter with AC Grid function.

High Power Inverter

The Mega-Guard High Power Inverter contains a 6 bridge high power 1700V-600A IGBT with controller board, including a Control Processor which is programmable in IEC-1131-3 language, Input/Output connections and a redundant Ethernet communication port.  The Mega-Guard HPI is water cooled and is available in different power versions. See below table and specification:

Efficieny: 98%
Cooling medium: water or water 50% / glycol 50%, seawater as option (20% power derating)
Maximum cooling inlet temp: 55 degr.C ; with a maximum of 10 degr.C increase at outlet
Power cables: through M50 SS cable gland (supporting up to 25mm inner diameter copper cable)
Ethernet and I/O cables: through M20 SS cable gland (supporting up to 8mm outer diameter cable)
Mounting and shock/vibration: in accordance with class for direct mounting on engine. IP67 protection

Battery Bank


The Battery Bank is modularly built with 52 VDC Battery Modules with capacity ranging from 100Ah to 400Ah. The Battery Module is based upon Lithium NCA technology which
has considerable lower weight and higher power density when compared to traditional LIFePO4 batteries. In addition the applied Panasonic battery cells  have long track record
and are widely used in electric cars. A typical single string Battery Bank consists of 14x Battery Module in series with a voltage of 728VDC and capacity ranging from 70kWh to 280kWh. Each Battery Module has a built in BMS (Battery Management System) complying with safety rules according DIN26262.
An overall Battery Management System is supplied as part of the battery bank charger (HPI-DCDC). The batteries are IP67 protected and can be bulkhead or rack mounted.

AC Grid and Shore Power

Most of the heavy consuming auxiliaries will be DC powered as well in order to reach the most economical operation. However, an AC grid will still be needed for common AC equipment. The Mega-Guard High Power Inverter with AC Grid function realizes an AC Grid with minimal harmonic distortion and also supports shore power connection. 

Sales and service

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Contact information

Praxis Automation Technology
Zijldijk 24A,
2352 AB Leiderdorp
The Netherlands

+31 (0)71 5255 353

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