INDUCTION MOTOR CURRENT ANALYSER
TYPE IMCA100

Squirrel cage induction motors are the robust work horses of industry. From time to time however damage can occur in the rotor cage, which may progressively worsen and can lead to catastrophic failure of the machine. The Induction Motor Current Analyser (IMCA) provides a simple means for maintenance engineers and operators to check the integrity of the rotor cage whilst the motor is still in operation.

This unique Analyser was originally developed by National Power.

• ANALYSES THE MOTOR SUPPLY CURRENT USING A CONVENIENT CLIP-ON PROBE
• ACCESS TO THE SUPPLY CURRENT CAN BE AT THE MOTOR SWITCHGEAR OR THE MOTOR TERMINAL BOXES
• MOTOR REMAINS IN OPERATION DURING TEST
• COMPACT AND EASILY PORTABLE
• CAN BE USED ON MOTORS WITH FLUCTUATING LOAD
• ANALYSER GIVES CLEAR, UNAMBIGUOUS INDICATION OF DAMAGE
• CAN BE USED BY UNSKILLED OPERATORS
• DISPLAYS NUMBER OF BROKEN BARS AND INFERRED ROTOR SLIP
  

PRINCIPLE OF OPERATION

The IMCA relies on the fact that the supply current spectrum of an induction motor with a damaged rotor contains a unique additional component, close to the supply frequency. A spectral analysis is carried out over a narrow band close to the supply frequency using a digital heterodyne and fast Fourier transform. The spectrum is then searched for the additional component. The interpretation of the result is shown on a display which can also give warnings of error conditions such as inadequate or unstable input signals. The process is fully automatic, the only action required by the operator being to input the number of rotor bars in the motor to the IMCA and define the degree of averaging required for the result. The IMCA can also be used if the number of rotor bars is not known with the number of broken bars being expressed as a percentage of the total number of bars on the display.

TYPICAL APPLICATIONS

Continuous monitoring of inaccessible high integrity motors.

Use as a routine survey instrument in plants with a large number of induction motors installed.

Monitoring can be carried out either at the motor or remote from it using current transformer signals.

Checking of motors on a manufacturer's test bed as a quality assurance check on cage integrity at the start of a machine's life.

The IMCA has been used by National Power and other users on a large number of induction motors of various makes in service. It has successfully provided an early indication of rotor damage on a significant number of machines.

SPECIFICATION

Ambient Temperature:    5°C to 40°C
Power Supply:               90 to 264V, 50 or 60Hz
Current Input:                10mA to 30A auto range with current probe
Spectral Range:            47-51Hz suitable for motors supplied at 50Hz or
                                    57-61Hz suitable for motors supplied at 60Hz
Enclosure:                     A two-tone grey metal case with adjustable carrying handle  
                                    Supplied complete with current probe and manual.
                                    A padded carrying case is available, if required.
Dimensions:                  W:  300mm  H:  150mm  D:  480mm
Weight:                         5.6kg

CONVEX DESIGN LIMITED
Unit 50, 60 Westbury Hill
Westbury-on-Trym
Bristol, BS9 3UJ, UK
Telephone/Fax: 0117 924 5591
email:sales@convexdesign.co.uk

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