Approximation method of the speed-torque mechanical characteristics using the spline interpolation of various electrical motors

Abstract

The design of the electric drives of the on-board installation requires motors of an adequate power. The dimensioning of the electric drive takes into account the mechanical loads and it provides the value of the torque which loads the electrical motor shaft. The selection of the appropriate electrical motors is based on the speed-torque mechanical characteristics, n = u(M), where n is the angular speed in rpm and M is the load torque in N · m · Drawing the n = u(M) characteristic, one can notice that the function is not injective, therefore we employ its ‘rotated’ version, i.e. the M = f(n) function. In this way we are able to mathematically define the … f function, and further on to deduce its approximation using the spline functions. As a case study we use an asynchronous motor for which the calculus is based on the Freidzon method that uses relative values. The spline approximation uses an original data processor which outputs various types of information in a wide range of text, image and computer code formats. Using the experimentally acquired data as input information in the spline based processor we have a more accurate approximation of the speed-torque mechanical characteristics. The previously mentioned methods are useful for the rapidly evaluation of the mechanical characteristics of the motors, that is an important criterion in the marine engineering decision making process.