Many of the tools needed for servo motor repair are available at a specialized electric motor repair facility. Listed here by priority, are some instruments and basic tools you will need to service servo motors.

Multi-Meters

Multi-meters as the name implies are used to make multiple measurements of voltage, current, and resistance. A good quality multi-meter is a basic requirement in servo repair. This may be either analog or digital but should of dependable quality. Preferably, both analog and digital would be available. The pictured multi-meter is an Extech Multimaster 560.

Meg-ohm Meter

Meg-ohm meter will be used for testing the quality of insulation and is used the same as it would be used in the repair of other electric motors. Care must be exercised that electronic circuits are not contacted during meggar testing of the windings. The test instrument would preferably have selectable voltages available for testing. The voltage used for testing should be near the rated voltage that the motor will see when in service. The pictured unit is an Amprobe AMB-4D with 250, 500, and 1000 volts selectable output voltage.

Oscilloscopes

Oscilloscopes are used to observe waveforms and timing differences of these waveforms. A good quality oscilloscope with storage and printout capability is one of the most used tools in the repair of servo motors. It should have a minimum of two channels. An oscilloscope with two isolated channels is very useful in testing circuits that do not have a common reference point. The unit pictured is a Fluke 196 digital scopemeter.

Variable Speed Motor Test Stand

Variable speed motor test stand to back drive the motor being repaired. A variable speed test stand for back driving the servo motor is necessary for working on brushless units. The permanent magnet rotors that are used in these motors cause the motors to become generators when they are driven. This counter generated voltage will be equivalent to the applied voltage when the motor is running. The alignment of the commutation, voltage level of the counter voltage, and waveform all are important to be able to verify. This test stand is used for these purposes.

Encoder / Resolver Test Equipment

Encoder / Resolver test equipment is used for pulse counts on encoder output and testing of pulse width and the relationships of these pulses to each other. The testing of serial encoder signals requires special decoding equipment to be able to read these signals. The angular position of a resolver may be determined at ninety degree increments with an oscilloscope. However, resolver to digital interface equipment will allow the angular position to be determined for all positions of the resolver. Pictured here is the Mitchell Electronics TI-5000R test

Servo Motor Drive Amplifiers

Servo motor drive amplifiers for test running of motors after repairs. The ability to test run a motor up to operating speed is useful to checkout the dynamic operation of the motor. Bearings, vibration, noise, rubs, and overall operating condition of the motor may be checked. Shown here is the Mitchell Electronics TI- 3000R test unit that will test run many different servo motors by processing the commutation signals and converting them to match a standard amplifier.

Signal Breakout Boxes

for looking at various feedback and counter generated voltages. The use of a signal break out box will give quick, easy and safe availability to the voltages and feedback signals with an oscilloscope. This may be done with test points brought out from a common connection point that is used for connection to the motor. Breakout boxes eliminate falling leads that can result in damage to the feedback components. The unit pictured is the Mitchell Electronics TI- 5250.

Continuous Solutions is a west coast high-power energy lab located in Portland Oregon. We specialize in testing, diagnosing and repairing servo motors for use in industrial settings. Our diagnostic process includes the following:

• Back EMF 

• Rated Torque 

• Servo Controller 

• Servo Programming 

• Calibration 

• Zero Positioning 

Most servo motors used in industrial setting use controllers that require speciality programing to properly diagnose and service. In most cases, repair shops will send these specialized parts out, only able to repair the motor itself. Continuous Solutions specializes in the design and prototyping of electric machines, and we have the capability to repair the most specialized servo motor and controller.