Tag Archives: Marc Phelps

Difference Between VFD, Servo Drive Repair

Posted August 31, 2016 by Pepper Hastings

Categories: Blog, Industrial Electronics Repair

Tags: ,

Servo drive repair differs from VFD repairs in several ways, including being a bit more difficult to troubleshoot. Also, servo drive repair usually requires that the servo be connected back to its intended system to ensure it's repaired correctly (something that's extremely difficult to replicate in repair shop conditions).

A VFD (variable frequency drive) is generally used to control a squirrel cage type motor, where both stator and rotor are of a wound type to create the magnetic flux.

Servo drives are used to control permanent magnet motors. They are called permanent magnet motors because they use rare earth magnets in the rotor to create a much higher magnetic flux for their given size. This enables the motor to create more torque in a much smaller motor size. This means the motor has a lower inertia to accelerate and decelerate much more dynamically than that of the asynchronous squirrel cage type motor.

servo drive repair

Servo drive repair can be more difficult to troubleshoot in a shop setting than a VFD.

On the controller side, the servo controller can calculate a complex path and maintain the position along that path with varying loads and speeds. Many servo controllers are multi-axis or can be daisy chained to make multi-axis moves to follow complex paths.

Because of these differences, a Servo drive repair is much different than troubleshooting a standard VFD.  When isolating the issue with a servo drive, you must consider the entire system, drive, cabling and motor.  It's difficult to troubleshoot a servo without all three of the main components present.  And since servo drives are designed to run a specific magnetic flux motor, it is close to impossible to test them outside their designed system.

Check These Prior to Servo Drive Repair

We've compiled a list of the top simple issues that should be checked before sending in your unit for servo motor repair. Please note this is not meant to be an insult: I very often spend time trouble shooting over the phone to eliminate simple errors or problems. Double check everything before electing to send in a motor for repair, otherwise time has been lost in both the shipping and evaluation.

  1. Occam's Razor: The simplest explanation is most often correct. Make sure everything is plugged in. Try turning your drive and controller off, and reboot.
  2. Check All Servo Motor Cables. Look for items such as Broken Wiring, Loose Connections, Dirty and Corroded Connectors - bad connections can interfere with the power and signals that are vital to proper servo operation.
  3. Check Overall Cable Conditions
  4. Check Grounds and Shields. Just because a cable is in good shape doesn't mean it is properly grounded. Keep in mind that grounds and shields are important for protecting signal wires from harmful noise that can disrupt feedback communication. Motor power grounds are important because they facilitate the tripping of over current protection devices. If a motor has an inconsistent ground that is not continuous with a drive ground the power cable can throw an unmanageable amount of noise onto a properly shielded feedback cable.


If all this checks out, then you probably have a servo drive issue that requires shop servo motor repair.  Use a repair shop that can help you isolate the problem, but as mentioned above understand it could require some additional testing at your sight AFTER it's worked on at the shop. If your repair facility also has industrial field service technicians, so much the better. They can can help you with onsite troubleshooting of servo systems.

Marc Phelps is manager of the Innovative-IDM repair facility in Houston. You can contact him at marc.phelps@iidm.com

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How Are Your Capacitors Doing?

Posted August 13, 2016 by Pepper Hastings

Categories: Blog, Industrial Electronics Repair

Tags: ,

Industrial electronics use Electrolytic Capacitors on control and power boards, power supplies and elsewhere inside the component. From our experience, unfortunately, capacitors are the most high-fail component in electronic devices. The great news is, a reputable repair facility can bring your component back to life.


Capacitors are some of the most fail-happy components in industrial electronics. Temperature extremes are a key reason.

VFDs use Electrolytic Capacitors in the DC Bus section. Capacitors store and release energy as needed within a circuit. Larger capacitors generally have higher current load-handling ability and greater charge storage capacity. These properties are well-suited for large VFDs because some A/C motors need a pulse of energy 300 to 500 percent of normal to get them going. A Bus capacitor in a VFD is used for this application. Capacitors are the most high-fail component in electronic devices.

Why Capacitors Go Bad

The caps can go bad due to age or temperature transients. Typically, the function a capacitor is to act as a power supply filter.  It’s comprised of two strips of aluminum foil (called plates) separated by a paper insulator.  The foil and paper are rolled into a cylinder and immersed in an electrolyte solution consisting of an ethyl glycol fluid. This electrolytic moist separator inside can and will dry out if the unit gets too hot, causing it to develop an internal short circuit. The capacitor can fail if its temperature routinely goes above 150 degrees Fahrenheit or below 32.

Also when large amounts of current flow into the capacitor, it causes the electrolyte solution to boil and turn into a gas. Once turned into a gas, pressure builds rapidly until, hopefully, the safety vent plug releases pressure. (Thus, the term “puffy caps”.) This rupture can be dramatic and destructive. Not only is the boiling liquid and gas hot, it is also corrosive and will damage any components covered by the solution. Under controlled laboratory conditions, measurements have been taken during a violent, large capacitor rupture.  The equivalent explosive force of half a hand grenade has been measured. Many of the violent failures have been captured by mad scientist types on video.

The dielectric oxide-insulating layer is created during manufacture.  However, it will deteriorate in the absence of a sufficient rejuvenating voltage, and eventually the capacitor will fail if voltage is not applied.  Maintaining the integrity of the dielectric requires the steady application of power.  When voltage is applied, the oxide layer is rebuilt.  The oxide layer thickness is the crucial factor to determine the voltage rating of the capacitor.  Otherwise, the oxide layer will break down under voltage and cause a spectacular failure.

By applying voltage to the capacitor on a regular basis, the oxide layer is “reformed”, and the integrity of the insulating characteristic is ensured.  In our experience, the maximum time between power ups should be no longer than one year, provided the equipment is kept in a dry location at roughly 70 degrees F. Large temperature swings require less time between power ups.

In conclusion, look through your shelves to see if you have any electronic equipment that has not been powered up in the last 12 months or what equipment is operating in extreme temperature swings. Do you have equipment like this? If the answer is yes, you should seriously consider sending it to a trusted repair facility to be checked out in a controlled environment.



Many repair facilities, like Innovative-IDM repairs offer a free evaluation on all repairs, and can determine if it time to “refresh your caps”.  As a part of any repair we do, we replace all capacitors more than 5 years old, or any showing signs of degradation. Don’t let a faulty cap result in downtime at your facility.

When he's not collecting on bets, Marc Phelps is manager of the Innovative-IDM repair facility in Houston. You can contact him at marc.phelps@iidm.com

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Purple Heart, Medal of Honor Plaque Honors Phelps

Posted July 14, 2016 by Pepper Hastings

Categories: IIDM Behind the Scenes

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Marc Phelps was honored by teammate Mark Brewer in an impromptu presentation this morning at the Dallas office.

Phelps, a Purple Heart recipient in Afghanistan, received a commemorative award put together by fellow Navy man Brewer. The framed collectible was personally assembled by Brewer, who is on the board of the Medal of Honor Host City program.

The ensemble includes a first day issue post card of the Purple Heart stamp, postmarked Aug. 7, 2007 in Washington D.C. The card and stamp are surrounded by the signatures of 14 living Medal of Honor recipients.

Included is the signature of the last living MOH recipient from the Battle of Iwo Jima in February 1945. Hershel Williams ,now 92, charged an enemy position of caves and pillboxes with his flamethrower.

Williams returned to the front several times over four hours with recharged flamethrowers and demolition ordinance, all while under heavy small arms fire. He fought the rest of the five-week battle before being wounded and removed from the front line.

About 25% of Innovative-IDM's employees are military veterans. Today, we saw one of those veterans appreciate another.


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Industrial Drive Repair: Replace or Repair?

Posted February 19, 2016 by Pepper Hastings

Categories: Blog, Electronics Repair, Industrial AC Drive, Industrial Electronics Repair

Tags: ,

Industrial drive repair is an important discussion point in most manufacturing facilities. Often, the discussion is whether it’s worth repairing a VFD. Or just buy a new one.

Industrial Drive Repair

Industrial drive repair can be a tricky decision. When should you repair vs. when should you go ahead and replace the VFD? Read more to find out.

VFDs (Variable Frequency Drives) have decreased in price over the years. And with standard VFDs, it’s often economical to replace rather than repair the VFD. A reputable VFD repair company will tell you up front when a drive just isn’t worth repairing.

Many VFDs ARE worthy of repair. Here are some examples where repairing and AC drive might be preferable to replacing it.

When Industrial Drive Repair Makes Sense

It’s a specialized VFD. Some plants have machines worth millions of dollars that have small, very specialized VFDs. Due to communication bus issues, spacing issues (or other application specific reasons) it’s just not feasible to replace them. Innovative-IDM and other reputable repair depots can repair these specialized VFDs and keep the machine running.

It’s a large horsepower unit. The larger the HP, the more likely it is that repairing the VFD is a better option than replacement. For one thing, the installation costs alone on a large HP VFD can be significant, often exceeding the repair costs. We see significant numbers of high horsepower VFD repairs at our repair shop.

Servos. Servo drives are, in general, expensive. They also tend to have application specific software and communication protocols and are often great candidates for repair.

There are large numbers of the specific VFD in the facility. Once you have spares, your maintenance personnel have experience on the units. Now you can use a drive repair company for backup; it might make more sense to stay with what you have and just repair the VFD s rather than replace with new.

We have many customers in this situation. They weigh the cost of the VFD repair, against the TOTAL cost of replacement, which includes things like spares, personnel training, etc.

So, what goes wrong with VFDs?

In general, VFDs are quite reliable. But like any piece of machinery, they have common break points that cause problems, such as:

Loose connections. Don’t laugh, it’s a major cause of VFD downtime. Check simple stuff first. Is a plug on the main circuit board loose? Check your connections before trying a more complex VFD repair.

Cooling Fans. Major cause of problems in industrial drive repair. Some VFD s will let you know about this, but most won’t until you begin tripping on over temperature. The overheating can, and almost certainly will, cause major issues long term. Check your fans often.

Electrolytic Capacitors. These have relatively short lives compared to other components. Overheating shortens it even more.

Power Semiconductors. These are less common, but drastic failures. If this happens, do NOT just replace the IGBT or Diode, find out why if failed. Or, you’ll likely just be replacing it again as soon as you power up.

VFD Software or programming. Was it running before you tried changing a parameter? Then put it all back to where it was and see if that fixes it. Don’t automatically install factory suggested software revisions until you back up what’s running. In general, if it’s running fine now, leave the programming alone.

Circuit boards. These are much less common industrial drive repair failure than one might think, but is often the first thing suspected when an inexperienced technician begins to repair a VFD.



We give firm VFD repair quotes at IIDM and provide free evaluations in our shop. Email me and I’d be happy to discuss your individual situation, or pass you along to one of our technicians for further discussion about whether it’s worth repairing your variable frequency drive, or replacing it with a new one. BTW, did you know that IDM stands for Industrial Drive Maintenance? Isn’t that the kind of repair company you want for your industrial drive repairs?

Marc Phelps is manager of the Innovative-IDM repair facility in Houston. You can contact him at marc.phelps@iidm.com

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Congratulations to a couple whose match truly seems made in heaven

Posted September 16, 2013 by Pepper Hastings

Categories: Employees, Innovative-IDM

Tags: , , ,


Who was more excited to make it to Beth's and Marc's wedding? BUZZ WAS. He wouldn't miss it for anything in the world. From trying to join his comrades for a flight to being hand fed from Tony Do.

.......................... Beth Phelps and Marc Phelps.............................

Just a note to say how happy we are for you. Wishing you a lifetime of the greatest joy, love, and happiness. Congratulations to a wonderful couple.

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