Diesel Electric Propulsion Systems

         

Whisperprop

Diesel electric propulsion Systems


System description and Components

The minimum components of the Diesel electric drive system are Generator, motor controller and electric drive motor. This minimum configuration is displayed in the schematic below:

Fig. 1) Diesel electric propulsion System

Generators:

The preferred generators for the propulsion drives are the AGT-DE generators (Extension DE for Diesel- Electric). These generators are all ac generators, there is no rectifier included. The nominal voltage is 400V, with 400Hz @ 3000 rpm. The voltage is not regulated and may vary depending on the load. Therefore this voltage cannot be used for domestic power!
The advantages of these generators compared with the Panda Standard Asynchronous (PSA) generators for domestic power:

· More compact and efficient
· T he speed can be adjusted to the optimal operation point
· D ifferent speed modes for high or low power
· D elta-Wye switching possible
· Combination with high Power Fischer Panda HTL-G battery charge converters for DC/AC Domestic power systems


In the typical configuration there are two operation modes:

AC Mode: Full power range to the drive up to the maximum Generator speed (e.g. 3000 rpm). The speed can be manual set to fit the actual power requirements
DC mode: The speed is controlled by the HTL-G Charge Converter, normally in

a low speed mode (e.g. 1600rpm). This mode provides o nly dc power to supply batteries and inverters. No propulsion is available.



PM electric motors:

The PM (Permanent Magnet) Motors are available in the power range 12 – 50kW, up to 150kW on request. All these motors must be supplied with nominal voltage 400V ac (250 – 480V AC) and need a motor controller ( e.g. frequency inverter or Fischer Panda BDC controller ).
Due to the PM motor technology every motor has the maximum performance at the nominal rev speed. The maximum speed of the motor has to be defined with the order and is fixed for every motor. The standard is 1200rpm, every other speed is also possible. With higher nominal speed more power with the same size of the motor is available. The torque of these PM motors is constant in the whole speed range.

Explanation of the motor indication:

The first letter A, B, C and D are synonyms for 1, 2, 3 and 4.
The following two numbers stand in addition to the first letter for the diameter of the motor stator package in millimetres.
The next group of three numbers stand for the length of the stator package
The two numbers of the third group shows the poles of the motor
The last two Letters indicate the motor versions: RT, LD, SD, CV, ....

Example:
A70-120-12-RT: Stator- diameter 170mm, Stator length 120mm, 12 poles, Version RT (reduction type)

At the moment the following motor versions are available:
BT: Bow thruster
RT: Reduction type without thrust bearing
LD: Ve r sion with integrated thrust bearing
CV: Clutch version with electro magnetic clutch
SD: Saildrive version. With the saildrive gear a transmission ratio of 1: 1,7 is included. At this time only the size B40 is available, up to 45kW due to the Saildrive gearing.
AZ: aziprop motor (also DE- Outboard)

These motors have no mounting or steering included. All this has to be build by the customer (e.g. rudder control). The motor only comes with one or two flange plates.
All motors are filled with oil and need an external cooling circuit with heat exchanger (except the Aziprop, which is cooled by the ambient sea water , and the Bow thruster motors)


Motor Controllers:

The motor controller is needed for the speed control and direction reversion (Joystick with center position and forward / backward position required). The PM motors cannot run without motor controller.

Up to 30 kW the BDC motion controller can by used. This is a very compact water cooled motor controller with supplement of two direct connected drive control levers.
The UD Series motor controllers are air- cooled and used for the power requirements above 30kW.







Domestic Power:

The agt generators are designed for the modern DC/AC systems. This means, in the dc mode of the Generator we use a HTL-G charge converter (Transformer with rectifier and VCS electronic) connected to charge the storage batteries. The converters are available in 12, 24 or 48V DC, each up to 280 A. Other voltages or currents on request.

The 230V ac domestic power is provided by the DC/AC inverter, e.g. Victron energy Phoenix inverter. With this technologiy domestic power is available at any time, even if the Generator is not running. If the power exceeds a specified load, the Generator starts automatically. The high power will be supplied direct by the Generator and the batteries will not be loaded.

Fig. 2) Diesel electric propulsion with Domestic Power

Fig. 2 shows the complete Diesel electric Drive system with Domestic power consisting of the following components:

1) AGT-DE generator
2) BDC motor Controller
3) PM electric motor in different versions
4) ac power distribution
5) HTL-G charge converter
6) Victron energy DC/AC inverters
7) Storage batteries

Multiple Victron energy Phoenix inverters may be switched together to a grid of 5 inverters of each 2,5kW for the total power of 12,5kW. A 400V three phase configuration of 3 or more inverters is also possible.


In addition the Victron energy Phoenix Multi plus inverters can also operate as high power battery charger, if shore power is available and provide advanced power and battery management.

This solution would be the best for generators up 30 - 40kW and a DC/AC system 4 – 8kW and more. (The Generator should be loaded with at least 40- 50%)

If dc power is needed also in the generator AC propulsion mode, an additional dc alternator (up to 2kW) or Fischer Panda HTG alternator (4kW) can be useful .

In some cases like constan t and high power loads, a second, small standard asynchronous Generator may be reasonable.


Power requirements / Generator rating

For sailing and displacement yachts the power of approx. 2,5kW per ton displacement is sufficient to reach the hull speed. For normal cruising speed (70 % of the hull speed) only 20% of this is needed (0,5kW per ton)

Fig. 3 shows the ratio of the potential motor performance to the prop shaft power (hull resistance). Example of Volvo Penta D2-75, Propeller: 3000rpm (engine) – 9,6kn, VH = 8,76kn
The lower curve displays the power requirement at different boat speeds. Also disproportionate power demand for speeds faster than hull speed (70% more power to get only 10% resp. 0,8kn more speed)

Fig. 3) Ratio motor performance to hull resistance

Even for bad weather the electric motor gives advantages , because the Generator can always run at its maximum performance point and the electric motor can provide full torque at every speed.

To fit the low power requirements at cruising speed the Generator can be slowed down manually or a second smaller Generator can be used for this to prevent the “light load problem”.

Ref-Search:Fischer Panda Generator, Fischer Panda Genset, Fischer Panda Electricial Generator

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