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Electric & Hybrid Propulsion System Integration

Hybrid Propulsion Systems for optimum energy efficiency of the vessels

Brunvoll specialize in compact and light weight hybrid solutions, taking the full responsibility of the system integration

Benefits of a Hybrid Propulsion System

Hybrid propulsion systems benefit of the best from two systems - the combination of electric propulsion and diesel drive.

The Hybrid system configuration is a fuel efficient and flexible system.

The system configuration may consist of various components depending on the vessel type and operation profile. Brunvoll has a wide range of configurations to meet the market demands.

The system is ideal for operations in ares with requirements for low noise and reduced local emissions, such as harbours and protected areas.

Brunvoll - your preferred System Integrator

Brunvoll specialize in compact and light weight hybrid solutions, taking the full responsibility of the system integration.

The wide range of different workboats and passenger vessels, require unique knowledge about the challenges.

Our wide range of system configurations consists of a  hybrid package for propulsion with hotel load supply and standardised charging solutions on shore.

An integrated system design with focus on control philosophy, fuel savings and easy operation.

Brunvoll scope of supply in System Integration 

  • Control systems for propulsion and manoeuvring
  • Generator / El. motors for propulsion
  • Generator sets
  • Battery package
  • Frequency drives
  • Converters DCDC DCAC
  • Brunvoll Triton-EMS energy management system
  • Battery system with BMS
  • Transformers
  • Charging system

How we design the optimised Hybrid Propulsion System

Information about actual operation profile and hull resistance data are the critical inputs to design the optimised hybrid propulsion configuration.

From this information we determine the power requirements of the electrical motors and the size of the battery system to suit the specified operation profile.

Experience in optimising light weight propulsion systems

Brunvoll Electric Propulsion Systems are compact and light weight solutions allowing for more space for cargo and passengers.

From decades of experience in propulsion system design we have gained extensive knowledge in utilising the available power in the most efficient way.

Brunvoll Triton Manoeuvre Chair

Hybrid Operation modes


Diesel mechanical operation of the propellers up to design speed.

The Electric motor/generator may be engaged for power generation to the switchboard, which may be used for battery charging or other consumers.


Electrical propulsion for slow steaming powered from battery. The rpm and pitch are optimized for maximum efficiency.

Hybrid mode

Combination of EL- mode on one propeller and DM-mode on the other.

It increases the redundancy of the vessel and makes it possible to operate with only one engine available.

Boost mode

Boost mode combines DM- and EL-mode for maximum power and speed. It makes it possible to select a smaller engine when max power is only needed incidentally.

Starter characteristics

Direct On-Line starter

Starting current:

5-10x Nominal motor current (IN)


Low price and high starting torque


High in-rush current


The Direct On-Line (DOL) starter consists of a contactor and a protection device such as a circuit breaker. The contactor is energized when the start button is pressed, and the full line voltage is connected to the motor. Motor is started with propeller in zero pitch position (IZP).

Click the images to enlarge

Star-Delta starter

Starting current:

2-3x Nominal motor current (IN)


In-rush current reduced with approx. 60% compared with DOL


Reduced starting torque


The star-delta starter method applies reduced voltage to the motor, thus reducing current, during startup. This method requires that both ends of motor winding terminals are available. When connected in star each winding has less voltage (1 / √3 ~ 60%), and thus will have reduced starting current and torque. When full speed is reached the motor is connected in delta, having full torque available. Propeller pitch can be increased, and load applied when motor is connected in delta. Motor is started with propeller in zero pitch position (IZP).

Click the images to enlarge


Starting current:

2-3x Nominal motor current (IN)


In-rush current reduced with approx. 60% compared with DOL


Reduced starting torque


Auto-Transformer also applies reduced voltage in steps to the motor during startup. The transformer voltage ratio can be designed to the application, typically having a 50-70% motor voltage during startup. The motor consumes less current at a lower starting voltage. For example, with a 50% tap on the Auto-Transformer, the motor draws half its rated current, or about 25% of what it would draw with a DOL starter. Motor is started with propeller in zero pitch position (IZP).

Click the images to enlarge

Electronic soft starter

Starting current:

2-2,5x Nominal motor current (IN)


In-rush current reduced 


Reduced starting torque.
Based on electronics


An electronic soft starter is a starting device that controls the way electricity is provided to the motor by using active switching devices such as thyristors. The device works in both in-line and in-delta configuration modes in three-phase motors. 

This starting method is ramping up the motor voltage in the starting sequence resulting in a reduced start-up current, allowing for a smooth and surge-free increase in motor torque. The voltage dips, stress, and wear and tear on the mechanical parts are all reduced as a result. Due to the thyristors there will be harmonic distortion of the current, and the influence on system voltage will depend on starting current and system impedance. Motor is started with propeller in zero pitch position (IZP).

Click the images to enlarge

Frequency converter starter

Starting current:

0,5x Nominal motor current (IN)


In-rush current reduced.
Full speed and torque control


THD generated, filters required.
Based on electronics


This is an electronic-controlled approach for starting asynchronous motors smoothly. It controls the frequency and current for the motor with electronics inverter circuits, avoiding large startup current. The thruster system's mechanical parts will be protected from high load because of the smooth start-up, and the this will also reduce the load on generators during startup compared to line-starter options. Depending on required performance torque and current may be below nominal values during startup. This is the high-end solution for the starting the thrusters, giving benefits such as smooth start, better energy economy, reduced wear and tear and process optimization.  Other benefits include motor speed stability during load changes and a longer motor life overall. Motor is started with propeller in zero pitch position (IZP).

Frequency converter starters may have different interface towards the main switchboard where 6-pulse rectifier is the most common, but both 12/24 pulse and Active Frontend (AFE) are used.6-pulse starters are the most common type, widely used due to the compact design and availability.The disadvantage with the 6-pulse starter is the increased THD during startup, particularly in smaller power system with large thrusters this might be an issue. 

To mitigate the THD a 12 or 24 pulse transformer and rectifier may be chosen, typically used for larger thrusters in larger ships. 
Frequency converter starters with active front end guarantees sinusoidal current and does not require a transformer. The AFE rectifier and LCL filter is more spacious than the 6-pulse rectifier and is suitable for high end solutions and ships with relatively small power system compared to thruster power.

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Olav Urbø

Olav Urbø

Sales Manager, Brunvoll Mar-El AS

+47 907 65 726
Birger Gauslå

Birger Gauslå

VP Sales & Marketing, Brunvoll Mar-El AS

+47 35 07 58 14

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