Temperature Measurements

This is a key indicator of a failing, or overloaded motor. You can use an infrared temperature probe to measure temperatures at key points, including: bearing locations, motor terminal block connections and the motor housing.

Overloading

This happens when the motor is trying to deliver more torque/power to the mechanical load than it is rated for. Use a clamp to measure the motor current and check it against the nameplate ratings.

Voltage Measurements

The voltage shown on the ASD display does not include the high frequency current that a scope or meter with a wide frequency response will measure. This results in measurements that are higher than expected. An instrument with a filtered input or a low-pass filter probe used with a scope can be used to verify that the voltage at the motor terminals corresponds with the ASD display.

Current Measurements

Current measurements are made in high energy-electrically noisy environments. The most flexible tool is an AC/DC clamp, but it must be optimized for use around ASDs. The other option, an AC only, current transformer (CT) style of clamp, will usually work best because it is a low-impedance device and less likely to pick up electrical noise. Also, be sure that any clamps you use are properly shielded to prevent problems from noise.

Fluke has a collection of free application notes, videos and brochures that provide information on the techniques and the tools for Troubleshooting Adjustable Speed Drives. For more information on ASDs and Fluke products, visit the Fluke website at ca.fluke.com or call 1-800-36-FLUKE.