Repair Bulletin Detail

Estimating the Life Left on Your Servo Drive

It is important to know how much life left on your servo drive so that you’re not caught by surprise. This is especially true if your unit is 8-10 years old, as that’s the typical time period in which we find most servo drives needing repairs.

One of the practical ways to test a drive’s reliability and remaining life span is to operate it under heavy load and stress temperature. A general rule for such prognosis: every 10 degrees in Celsius temperature increase is equal to 1 year of life. So, considering the drive usually operates at 50-60 degrees, one that passes tests at close to 90 degrees will probably operate for at least another 3-4 years without problems. (Worth noting: the internal protection disables the drive at 90 degrees.)

Drive Life Span is Tested During Preventative Maintenance

MSI handles this test during as part of our drive preventative maintenance service. The process involves disconnecting the cooling fans, loading the drive to maximum specifications, and then letting it run on a stator at maximum current until thermo protection turns off the drive. A word of caution: this isn’t a test that should be attempted by just anyone, because it requires access to very specific equipment and detailed knowledge of drive’s circuitry. MSI is fortunate to have the manufacturer-provided equipment, schematics and procedures that are required for testing a drive’s abilities to the limit.

Adjusting All Circuits Improves Performance

We also make sure during preventative maintenance that all circuits are adjusted according to factory specifications. This is extremely important on account that all drives require adjustments to which the end customer or field engineers do not have access. They are set at the factory and their adjustment requires very specific knowledge of involved circuits and tuning procedures. Such adjustments shouldn’t be handled by others repair centers, given that they lack access to the original documentation and schematic diagrams.

Examples of some extremely important circuits affecting drive performance are: the current sensor circuit providing current feedback for each motor output and regulating the drive’s power stage and the resolver feedback circuit feeding the motor’s velocity/acceleration/position data to microprocessor.

Proper fine tuning to factory specifications significantly improves a drive’s performance, allows operating across a wide temperature range and up to maximum power, while prolonging the life of the drive.

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Estimating the Life Left on Your Servo Drive