The answer to this question appears at the end of this newsletter.

Replacing Motor Drives
Motor drives are reliable, but they can fail. Often, the point of failure is a transistor (SCR in the older drives) -- typically an IGBT. A quick replacement, and you're up and running, but the failure can be more severe, requiring a total drive replacement.

A drive upgrade is almost always beneficial. Motor drives keep getting better, smaller, and cheaper. Each new generation solves or reduces some problem in the previous generation.

With all the various motor drives on the market, how can you pick the right one? Contact your electrical supplier or the drive manufacturer for assistance, and have this information ready:

• Nameplate data from the motor
• Nameplate data from the existing drive
• Cable distance between the drive and the motor
• Photo of motor and drive, as installed
• Brief description of the application
• Brief description of the failure and what you found per the troubleshooting steps in the manual.

You may want to look at what your electrical supplier has in the way of starters or other motor controls. You may find some connectivity features, for example, that allow you to provide input via your network to an operator console. Or you may decide on a different model of starter that provides more compactness and will allow you to centralize starters in a common cabinet. If you've got individual starter enclosures scattered all over the production floor, consider consolidating these into a central location to reduce footprint clutter. You could do that with NEMA starters or with IEC starters.

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Change-Outs
Decontactors are a combination plug & receptacle and disconnect switch. They allow electrical equipment to be safely and easily disconnected and connected - up to 60 hp or 200A. Since there is no access to live parts workers can change out a motor without having to 'suit-up'. Inquire about our free trial program.
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NEC at the Facility
What's the difference between Art. 280 and Art. 285, and what does it mean for your facility? To answer that, you need to know the difference between surge arresters and surge suppressors.

Surge arresters limit surge voltages by discharging or bypassing the current. Surge suppressors limit transient voltage by diverting or limiting the current. These are distinctly different methods that accomplish distinctly different goals.

Difference in application: Surge arresters prevent the voltage from rising above a level the suppressors can handle. Surge suppressors then reduce the voltage to a level the equipment can handle.

The typical application for surge arresters is before the service (e.g., a spark gap arrester), to prevent large transients from entering the facility. Surge suppressors (e.g., TVSS device), which are applicable only to circuits of 600V or less, are used downstream of that.

From an engineering standpoint, applying Art. 285 without any Art. 280 protection exposes the TVSS to more energy than it can handle. To avoid sacrificing both equipment and TVSS, start with a one-line and note the points where each kind of protection applies. For TVSS, you will probably need multiple units at staged energy levels for cost-effective protection.

The Practical Implications of OSHA 1926.416
This passage focuses on the idea of protecting employees from energized equipment. Some of the key points include:

• If you must work near a circuit with which you could make contact, de-energize it and then provide proper grounding or guarding.
• When removing fuses, use a tool rated for the voltage.
• Keep workspaces and walkways clear of cords.
• Don't use frayed cords.
• Don't fasten extension cords with staples, hang them from nails, or suspend them with wire.

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Quiz Answers
Answer to Electrical Troubleshooting Quiz
You might be tempted to assume both drives failed for the same reason, but that's not what happened. The observation that "it performed flawlessly for years" is a clue that the first drive failed probably due to a power event or other transient cause. This is also a clue as to the age of the replacement drive. Capacitors hold a charge for only so long. Before putting a spare drive online, you need to put the DC link capacitors through a recharging process. Consult your drive manual or the manufacturer for information on how to do this.