The inherent complexity and nonlinear nature of the dynamic representation of an induction motor-operated centrifugal fan/pump (CFP) system hinders the systematic closed-loop control design for flow rate ( \(Q\) ) and pressure/head ( \(H\) ) regulation, widely used electrical energy-efficient solution in fluid transport infrastructures and designed intuitively nowadays by practical electrical engineers under the implementation constraints of industrial AC drives. This paper derives the system model allowing direct application of analytical closed-loop control design methodologies, avoiding heuristic solutions and it succeeds in the linearization of an experimentally validated nonlinear six-order dynamic representation of the fan coupled with a scalar-controlled induction machine for an arbitrary operating point. It also reduces the model order via derivations in the stator voltage vector reference frame. The results are verified via simulations and experiments. The analytically derived control-oriented linearized model is of third order and relates small deviations of the stator voltage frequency to the corresponding small deviations of the \(Q\) and \(H\) , suitable for scalar induction motor regulation applications. The model is presented as block diagrams, in state-space representation and computed as transfer functions. Simulated step responses of the linearized and nonlinear models are close and in good agreement with experimental data. Overall, this paper, for the first time, linearizes and reduces the order of the experimentally validated nonlinear model of the fan-induction motor system accounting for the fan’s own dynamics. The obtained model is suitable for analytical closed-loop control design by practical electrical engineers, with following implementation based on industrial AC drives.
