Distributed diagnostic system

An apparatus for locally monitoring a rotating electric machine for diagnostic purposes, the apparatus comprising:

• a set of sensors positioned with respect to the rotating electric machine to provide sensor information indicative of the operation of the rotating electric machine, at least one sensor of the set of sensors being an environmental sensor for providing environmental information indicative of an environmental condition of the machine;
• load determination means for generating machine load information indicative of a machine load;
• and
• a programmed processor for receiving the sensor information from the set of sensors, normalizing the sensor information based on the machine load information and the environmental information to provide normalized information that is independent of the machine load and the environmental condition of the machine, and for processing the normalized information to provide an output signal indicative of the diagnostic condition of the rotating electric machine.

An apparatus for locally monitoring a rotating electric machine for diagnostic purposes, wherein the rotating electric machine includes an insulated phase winding, the apparatus comprising:

• a programmed processor;
• and
• a set of sensors having outputs coupled to the programmed processor, each sensor being positioned with respect to the rotating electric machine to provide output information at each output concerning the operation of the rotating electric machine, the set of sensors including an insulation failure sensor comprising:
• a conductive element having a first end and an uninsulated conductive portion that is wound about a portion of the insulated phase winding;
• and
• a detection circuit coupled to the first end of the conductive element for detecting the presence of an electrical connection between the uninsulated conductive portion and the portion of the insulated winding, thereby detecting an insulation failure,
• wherein the programmed processor (i) receives the output information from the set of sensors and normalizes the output information to provide normalized information that is independent of the machine load or the environmental conditions in which the machine operates, and (ii) processes the normalized information to provide an output signal indicative of the diagnostic condition of the rotating electric machine.

An apparatus for locally monitoring a rotating electric machine for diagnostic purposes, wherein the rotating electric machine includes at least one bearing structure and a phase winding, the apparatus comprising:

• a programmed processor;
• and
• a set of sensors having outputs coupled to the programmed processor, each sensor being positioned with respect to the rotating electric machine to provide output information at each output concerning the operation of the rotating electric machine, the set of sensors including:
• at least one sensor positioned to provide an electrical signal corresponding to an ambient temperature of the bearing structure;
• at least one sensor positioned to provide an electrical signal corresponding to a temperature of the phase winding;
• and
• at least one sensor positioned to provide an electrical signal corresponding to a temperature of the environment in which the rotating electric machine is operating,
• wherein the programmed processor (i) receives the output information from the set of sensors and normalizes the output information to provide normalized information that is independent of the machine load or the environmental conditions in which the machine operates, and (ii) processes the normalized information to provide an output signal indicative of the diagnostic condition of the rotating electric machine, and
• wherein the programmed processor normalizes the bearing structure and phase winding temperature information to provide normalized temperature information that is independent of the machine load or the environmental conditions in which the machine operates, in accordance with the following equation:
• TN=(Tsensor−Tambient)/L
• where, TN, represents the normalized temperature information;
• Tsensor represents the raw temperature reading from the appropriate sensor;
• Tambient represents the ambient temperature of the environment;
• and L represents the machine load.

Apparatus for producing an electrical signal indicative of the rotational speed frequency of the rotor of an induction machine comprising:

• a flux sensor positioned to provide an output signal that corresponds to the flux in the induction machine;
• a comparator having an output, a first input and a second input, the first input receiving a reference voltage signal and the second input receiving the output of the flux sensor, the comparator producing at its output a signal having a first logic state whenever the voltage at the first input is greater than the voltage at the second input and a second logic state whenever the voltage at the second input is greater than the voltage at the first input;
• and
• means coupled to the output of the comparator for producing an electrical signal corresponding to the frequency at which the output of the comparator changes states, wherein the electrical signal is indicative of the rotational frequency of the rotor.

A method of determining the slip of an induction machine having a rotor and a stator, the rotor defining a rotational frequency and the stator defining a synchronous frequency, the method comprising the steps of:

• monitoring the flux passing through a portion of the induction machine and providing an electrical signal corresponding to the flux;
• deriving a first digital signal corresponding to the frequency at which the electric signal corresponding to the flux varies from above a predetermined value to below the predetermined value, the first digital signal corresponding to the rotational frequency of the rotor;
• determining the major frequency component of the electrical signal corresponding to the flux and deriving a second digital signal corresponding to the major frequency component, the second digital signal corresponding to the synchronous stator frequency;
• and
• determining the slip S of the induction machine in accordance with the following equation:
• S=(f(s)−f(r))/f(s)
• where f(r) is the rotational frequency of the rotor, and f(s) is the synchronous stator frequency.

A monitoring device for use in monitoring an electric machine, the monitoring device comprising:

• a programmed processor;
• and
• a set of sensors having outputs coupled to the programmed processor, each sensor being positioned with respect to the electric machine to provide information at its output concerning the operation of the electric machine;
• means operatively associated with the programmed processor for operating the processor in a birth certificate mode wherein the outputs of the sensors are processed by the programmed processor and stored as baseline operational parameters;
• means associated with the programmed processor for operating the device in a monitoring mode, after the programmed processor has been operated in the birth certificate mode, wherein the programmed processor processes the outputs from the sensors, compares the processed outputs to the baseline operational parameters, and provides an indication of the diagnostic condition of the electric machine based on the comparison.

A method of determining the load characteristics of an electric machine, the method comprising the steps of:

• using an electrical sensor set to periodically monitor the temperature of at least a portion of the electric machine and the rotational speed of the electric machine at given points in time over a first extended period and, for each point in time, storing in a digital memory a data couplet containing information concerning the temperature, the rotational speed, and the point in time;
• using a digital processor to identify couplets having temperature values within a predetermined temperature range;
• and
• providing an indication of a steady state load if the temperature readings for at least a first predetermined number of couplets are within a first predetermined temperature range and the speed readings for the at least a first predetermined number of couplets are within a first predetermined speed range;
• or
• providing an indication of an ON/OFF load if, for at least a second number of couplets, the following condition is true:
• speed at k−3=speed at k−2=speed at k−1=speed at k and temp at k−3<temp at k−2<temp at k−1<temp at k, where k corresponds to the time of the couplet, and k−x corresponds to the time of the xth preceding couplet.