How to Test a Servo Motor

Posted on 3/7/2021

Our servo motors are designed to meet the rigorous demands of the manufacturing industry, but like any piece of machinery they can sometimes experience problems that affect performance. One of the most common culprits of servo motor failure is short circuits in the windings.

Diagnosing electrical problems in your servo motor is a simple, straightforward process. With a few tools—megaohmmeter, ohmmeter, or multimeter—and the right knowledge, you can check your servo motor and troubleshoot this basic issue.

FIRST, BE SURE TO DISCONNECT ALL POWER TO YOUR SERVO MOTOR TO PREVENT INJURY!

Test Your Servo Motor for a Short or Open Circuit

One of the easiest ways to test and troubleshoot a servo motor is by looking for any short or open circuits that exist within the system by testing all three wires (T1, T2, T3) to the ground wire. The steps vary slightly depending on what type of meter you use.

Using a Megaohmmeter

• Place the positive lead onto T1 and the negative lead to ground. Go back and repeat these steps for T2 and T3.
• Make sure the leads on both ends are not touching anything else, including other leads.
• Each phase should measure between 600 to 2,000 megaohms.
• If the resistance reading is 0 or shows a low resistance (20 and under), you likely have a short in your system.

Using an Ohmmeter

• Start by disconnecting lines T1, T2 and T3 from the drive.
• Using your ohmmeter, begin by testing while the cable is still connected to the servo motor.
• If the reading on your ohmmeter is 0, you likely have a short in your servo motor.
• Next, disconnect the cable and test the servo motor and cable alone.
• Make sure the leads on both ends are not touching anything else, including other leads.

Using a Multimeter

• Set the multimeter to the ohm scale (to measure electrical resistance) and zero it out by touching the two leads together and pushing the reset button.
• Follow the same steps for using the ohmmeter (above).

Test Your Servo Motor for a Short or Open Circuit Between Phases

Using a Megaohmmeter

• Start by testing the connections between T1 to T2, T2 to T3, and then back to T1 to T3.
• You can expect to see a range between 0.3 and 2.0 ohms with 0.8 ohms being the average.
• If you get a reading of 0 there is a short between the phases.
• If you get a reading of infinite or 2000 ohms and above, it is an open short.

Check Out These Related Blog Posts

•       When to Repair or Replace Your Servo Motor
• 8 Signs Your Motor Needs Servo Repairs
• Simple Things to Check Before Sending in Your Servo Motor for Repair