Servo drives are used to control devices including
robotics, model airplanes, aerospace technology and multiple industrial
applications. The drive is a component in a closed-loop system, and uses an
amplified control signal to send power to the device motor. They are
primarily used to control the output torque, speed and position of a motor
shaft.
Most servo drives in use in 2017 are digital, and
like all other electronic equipment, they can malfunction at the most inconvenient
times. A breakdown can disrupt an entire production schedule and cause
significant loss of revenue, or it can cause problems like overheating and
result in damage to the systems it supports.
Common Problems with Servo Drives
Most of the typical servo drive issues you’re
likely to experience have common causes, which helps to make troubleshooting
less frustrating. Here are some malfunctions to watch for:
- System instability: If any of your settings are incorrect, the servo drive may not operate correctly. There are numerous parameters to check related to motor tuning as well as speed and current loops. If you’re getting noise transmitted into the control wiring, you’re likely to see erratic movement of the motor shaft.
- Inability to reach the right levels of acceleration or deceleration: This can occur for several reasons, such as when the servo amplifier’s capabilities are insufficient for the system inertia, or the friction is excessive.
- Not responding to a velocity command: The reason for a lack of response is usually easily identifiable, and common causes are problems with the control interface, system or motor malfunctions, incorrect voltage supply (or none at all), or the motor thermal protection has tripped.
- Noise on signal wires: This is typically caused by incorrect wiring or grounding, but can also be caused by electromagnetic interference from nearby equipment.
- System runs uncontrollably: This issue develops when there are problems with the velocity command signal, when the motor speed/position feedback signal is erratic or missing, or when there is an internal malfunction in the servo drive.
 |
| AN EXAMPLE OF A MOTOR DRIVE SYSTEM |
Troubleshooting: What to Look
For
Correct identification of the problem is critical
for effective troubleshooting of your servo drives. Here are some tips on how
to go about determining causes of common issues, and measures you can take
to try and resolve them.
#1: Review the display on the drive. If it
doesn’t come up, check the power supply. If you see an alarm on the display,
use the instruction manual to investigate the possible causes.
#2: Verify that the feedback device (resolver,
encoder, etc.) is functioning properly. Use an oscilloscope to check
waveforms and pay special attention to noise, missing channels, incorrect wave
shapes, or low levels. Look for breaks or bad splices in the feedback cable.
#3: Check the line voltage to ensure that the
incoming power to the drive is balanced and the correct voltage. For
common DC bus systems, check the intermediate dc voltage as well. Use an oscilloscope
to check for noise, voltage fluctuations, etc.
#4: Don’t forget the possibility of a mechanical
problem. Problems such as friction or vibration in the machine can cause issues
in the servo drive and motor.
Run all the tests recommended in the manual and
record the results for future reference. If these initial measures don’t work,
it’s time to consider getting a professional service company to help.
You can also read: Stepper and Servo motors
About the Author
With over 25 years of experience in the industrial
automation repair industry, Jeff Conner is the Dallas Service Manager for
Control Concepts and serves on the Advisory Committee for the Electronics
Technologies Department at Texas State Technical College. Control Concepts
offers around the clock service and support anywhere you need it. To learn
more, visit http://www.controlconceptstexas.com
For Timely Instrumentation & Automation updates, join our Newsletter List
No comments:
Post a Comment