DE909599C - Electric ship propulsion with one or more synchronous generators and one or more AC motors - Google Patents

Description

Electric ship propulsion with one or more synchronous generators and one or more AC motors when reversing ship propulsion units like a ship's propeller, a comparatively great must shortly before it is overturned high torque can be overcome because the moment of the screw from the kinetic Energy of the still moving ship is maintained. With the departure of the ship this torque decreases with every screw speed. With electric drive With rotary field machines, the motor torque is determined by the level of excitation, only the generators are energized, but the motor works as an asynchronous motor. The excitation of the generators must be practical to achieve a sufficiently high engine torque can be increased far above the nominal value, thus with the high slip value of the motor the reactive power is covered and thus the real power that can be drawn from the prime mover is transmitted to the engine.

To change direction, one usually switches on the shock excitation immediately, which in itself results in the highest torque of the engine. By applying this In the process, however, the reversal process is by no means the cheapest or the fastest carried out because the counter torque of the propeller is very large and only with the onset of the braking effect, i.e. smaller with decreasing ship speed will. Also the peak torque of the screw, i.e. H. that while reversing a propeller drive at about 40% of the engine speed occurring highest counter-torque decreases with time and must with immediate Use the excitement to be overcome in full. Practical lies in many Cases the peak torque at full ship speed in the same order of magnitude like the torque applied by the engine, and therefore there is a risk that the engine stalls. The engine does not change the engine speed itself, but only caused by the change in the ship's speed. Only with the screw torque decreasing due to the drop in the ship's speed is slowed down until the peak torque is overcome. But there the getting stuck of the motor takes place at a slip value of the motor which is greater than one, see above a lot of heat is generated in the start-up cage of the drive motor; also be the stator windings of the motors and generators are highly stressed.

The change of direction would have to take into account the above the slower it is carried out, the easier it is. When maneuvering has the supply of the motor in the old direction of travel with the reverse The rotating field direction also results in a braking effect when the motor torque is still is smaller than the screw torque. In this reversing process that works without shock excitation the braking effect is naturally low and the screw only hits after it has dropped the ship's speed and the peak torque, so that the time span from the beginning of the reversal process to the turning of the screw is much larger is than when braking with shock excitation. The delay, which is desirable in itself the excitation can occur even with known arrangements. One increases z. B. the excitation voltage thereby. that by an additional machine an additional voltage is inserted into the excitation circuit, then the field must be, thus also the Only build up the voltage of this additional machine when the machine is switched on, what takes a certain amount of time. Also the cessation of arousal with the help of a Variable resistance during reversal can delay generator excitation condition. however, since these delays are unintentional, they are perfect arbitrary and uncontrollable.

To the disadvantages inherent in the known maneuvering processes eliminate and use the benefits of a delay in any case according to the invention, the delay of the excitation as a function of the screw speed, namely the excitation of the generator or generators approximately from the time of Beginning of the reversing process depending on the speed of the or the Ship propellers by introducing a counter voltage into the excitation circuit of the or the generators or excitation machines so delayed amplified that only briefly before the propellers overturn, the predetermined maximum value of the overexcitation is achieved. The screw torque then goes through the action of this braking effect back in the entire speed range, i.e. also at the speed at which the peak torque occurs. This ensures that the peak torque of the screws, even if at full ship speed it is higher than the available engine torque, is run over without the motor getting stuck.

One might now assume that the delay in excitement is more severe Dependence on the screw speed at low ship speeds one unwanted lengthening of the changeover time would be necessary, as in these cases the peak torque of the screw is inherently small and easily relieved by the engine can be overcome. However, if you take the counter voltage from an additional one Exciter that opposes the main or auxiliary exciter and is coupled to the motor to be reversed or to one of the screw speeds proportional speed is driven, so is also at low ship speeds an extension of the reversing time does not occur, since also with decreasing speed the counter voltage introduced into the excitation circuit decreases. The Counter-exciter bridged and not excited. When the maneuver begins, the short circuit eliminated and the machine brought to a voltage that the The voltage of the main exciter partially removes. This is then already for the full shock excitation set.

A self-excited counter-excitation machine is particularly favorable because it in the voltage collapses at low speed, the counter excitation is then not when reversing from a low initial speed of the screw motor effective. This is very useful because then the counter torque is also in proportion to the engine torque is small.

The counter exciter can also be in the exciter circuit of the main exciter of the three-phase generator. In this case, the auxiliary machines receive and the control device, which the counter-excitation after reversing the drive member and prevents in continuous operation, small dimensions. The counter excitation machine can further by means known per se, e.g. B. by an auxiliary power winding, a get a particularly suitable characteristic.

Claims (4)

PATENT CLAIMS: I. One or more electric propulsion systems Synchronous generators and one or more AC motors in which during of maneuvering the generator excitation is increased, characterized in that the excitation of the generator or generators approximately from the point in time at which the reversal process begins on depending on the speed of the propeller or propellers by inserting one Counter voltage in the excitation circuit of the generator or generators or excitation machines is amplified with such a delay that only shortly before the propeller turns the maximum value of overexcitation is reached. 2. Electric ship propulsion according to Claim I. characterized in that the counter voltage introduced into the excitation circuit is taken from an exciter, which is coupled to the motor to be reversed or is driven at a speed proportional to the screw speed. 3. Electric ship propulsion according to claim I and 2, characterized in that the counter-excitation machines are self-excited. 4. Electric propeller drive according to claim I and the following, characterized in that the counter-excitation is ineffective during the approach and continuous operation of the ship.