In some industrial induction motor driven
rotational systems/applications, it is important to know the
key mechanical parameters, namely, the total moment of
inertia and the Coulomb, viscous, and air/fan friction
coefficients. These parameters can be useful to adjust PID/PI
controllers, to detect abnormalities/faults in the system
operation and/or to estimate the industrial process state. If the
estimation is performed in-service without decoupling the
motor from the driven system, it is of great interest because it
allows detecting changes in the mechanical system
characteristics. An example where this concept can be useful is
in industrial mixers, where the viscosity of the paste being
mixed (e.g., concrete) can be estimated and used to determine
the state of the mixing process. In this paper, a novel, in-field,
nonintrusive, online method to estimate the mechanical
parameters of three-phase squirrel-cage induction motor
driven systems, is proposed. It is based on the open-circuit
motor terminal residual line-to-line voltage waveform change
analysis, after disconnecting the motor from the power
network. This analysis can be used to estimate the rotational
speed response of the system, further used in the mechanical
parameter estimation. Motor and system mechanical
parameter segregation can be achieved using motor nameplate
and datasheet data and/or air-gap torque estimation, before
disconnecting the motor.