SHIP ELECTRIC PROPULSION MOTORS COMPARISON

This article aims at defining and explaining relevant factors important for the evaluation of electric propulsion motors such as efficiency, length, diameter, weight, power factor, price, reliability, fault tolerance, maintenance, compatibility with frequency converters, as well as weather, corrosion, vibration and shock resistance. On the basis of these facts, the advantages and disadvantages of the commercially used squirrel cage induction machines and synchronous machines are analyzed. Among the synchronous machines, standard motors with field coils - brushless and with slip rings - as well as the radial flux permanent magnet motors are taken into consideration. The motors are compared from both the point of podded drive and the shaft line propulsion. The conclusion is that for podded drives, permanent magnet synchronous motors are the best option, although the use of the squirrel cage induction machines, mainly because of their much lower prices, might be profitable for smaller units. In the case of direct shaft line electric propulsion with very high propulsion power and low turns, synchronous motors with field coils and slip rings are still the best choice, while for geared shaft line propulsion with lower propulsion power squirrel cage induction machines could be recommended.