An engineering manager who works at Smith Services, one of the sister brands that work with us and are a part of Timken Power Systems, answers some questions regarding medium voltage industrial motors and motor repair.


Q: As an engineering manager at Smith Services, what does your job entail and what are your qualifications?

A: I manage everyday electrical and mechanical engineering operations at Smith Services. I earned a dual degree in electrical and mechanical engineering.


Q: How does Smith Services compare to other repair companies in the industry? 

A:Smith Services is very active in the EASA community. EASA (Electrical Apparatus Service Association) is a leading resource for providing specifications and standards for electric motor repair or electrical mechanical equipment. Their website probably lists over 1,000 service centers in the United States, so there are a lot of competitive repair shops in the country. Most motor repair services are local, and most shops generally work on small, low voltage rated motors. Smith Services is the largest electric motor repair shop in the eastern-half of the United States, and we are prepared to repair a wider range of motors and offer a wider range of repair services to our customers.


Q: Can you go into some detail regarding medium voltage motor classifications?

A: Medium voltage motors are classified through voltage ratings. 2,300 volts is a common voltage rating for motors in this class, with others ranging between 1,000 volts and 13,800 volts. Common industrial voltages, like 240 volt or 480 volt motors, are usually used for sub-hundred horsepower applications. But for larger horsepower equipment, lower voltage ratings become cost prohibitive to operate. By switching to higher voltage systems, and making allowances for additional insulation protection, it is possible to achieve exponential gains in efficiency.


Q: What applications are medium voltage motors commonly used for?

A: For industrial operations that range from 200-300 HP, up to 700 HP, medium voltage motors are the preferred option. There is an even distribution of sub-600 voltage equipment and equipment that runs on more than 1,000 volts. When additional horsepower is required, most facilities will use medium voltage motors or larger. For mission-critical applications, medium voltage motors are often the preferred choice because of their efficiency, reliability, and savings in operating costs.


Q: What criteria do you use when selecting a motor?

A: The specific application requirements guide the criteria for selecting a motor. The application type and its associated operational details determine the best option. Because compressors are usually highly stressed components, thermal control is a key factor in motor design. Pumps and fans will have specialized requirements, and unique mechanical engineering is required for belt drive applications because of the significant amount of radial loading. Motor selection for specialized equipment like centrifuges also requires considerable expertise with their own set of detailed design requirements.


Q: Do industries typically use medium voltage motors in their daily operations?

A: Yes, medium voltage applications are widely used in every major industry. For example, medium voltage motors are used in petrochemical, pulp and paper, metals manufacturing, and power generation processes across the country. Fifty years ago, industries depended on their location, and industries like pulp and paper mills were built in areas that were located near water sources, with less regard for the power infrastructure. Now, new plants select a location that optimizes their use of the power grid for medium voltage motors.


Q: Do most motor repair facilities provide medium voltage motor repair services? 

A: No. Most repair services are highly localized, and very few are equipped to service medium voltage motors. There are also repair companies that focus on high voltage equipment, 13,800 volts and higher, and these repair companies are also much less common. Smith Services can conduct all of the necessary electrical tests in the field, troubleshoot breaker systems and transformers, and more. Our highly trained staff is prepared to work on-site or in a highly equipped machine shop.

Specialized onsite large motor repair is available in cases where the equipment is not cost feasible to transport. A full array of large motor repair or large generator repair services can be provided in-house for medium voltage equipment. While we focus primarily on electrical motor repair services, such as servicing the driver, switchgear, and repairing the transformer, our association with the Timken Power Systems’ network allows us to provide our customers access to the large motor facilities in the network. With an expanded scope of capabilities, Smith Services can repair medium voltage motors and equipment for nearly three-quarters of the eastern United States within eight hours.  


Q: Can you describe some of the details regarding Smith Services’ load testing and spin test capabilities?

A: To carry out validation testing for medium voltage motors, a facility needs ready access to available power sources and apply them to that particular motor. Access to properly calibrated power sources with a dedicated 2,500 KVA test center gives Smith Services a distinct advantage over their competitors. All of the medium volt classifications can be tested with a dedicated such as 13,800 volts, 7,200 volts, 4,000 volts, and 2,300 volts. A dynamometer capacity of 12,000 lb-ft of torque, equates to 2,500 HP at 1,200 RPM, making it possible to test a 5,000 HP motor with a full complement of documentation at proportional values.


Q: What are terms of the warranties at Smith Services? What is your approach to maintenance?

A: Smith Services is highly experienced and well respected in the industry. We are confident in the level of repair services we provide for any of the motors we service, so our customers receive up to 6 months on the shelf, and a year in service for low voltage or medium voltage, whether they have large motor or large generator ratings.

We made some short term exceptions for manufacturers involved with random wound equipment in medium voltage, in a 2,300 volt class, because the OEMs pushed the design envelope, and were notoriously difficult to repair. Any time the voltage is increased, there is a proportionally increased requirement to contain the voltage, and additional insulation is required. Advances in insulation material technology have made it possible to offer durable, reliable solutions.

Cleanliness is a key part of maintenance for any facility. For a repair company, this means routine inspections for all large industrial motors. Motors need to be cleaned when they get dirty, and whether it is a simple blow down or inspection, routine electrical tests will indicate cleanliness problems. This data can also be used as predictive maintenance, which is especially important for large motors and applications running mission critical operations, because outages can be scheduled in advance, and inspections can be conducted onsite before removing equipment for repairs. The higher the voltage rating, the lower the current rating, so good maintenance is even more important for large voltage motors, because, while there are significant gains in efficiency, extra measures have to be taken to add more insulation to contain that voltage or pressure.


Q: Can you describe how the footprint of the equipment, the voltage rating, and the horsepower rating interact? 

A:  The footprint of a motor is driven by the torque output. Here is a common example. A 100 HP large motor rated for 1,800 RPM will produce 300 pound-feet of torque. Almost 1,800 pound-feet of torque can be produced when the speed rating is changed to 300 RPM with the same 100 HP motor. Additional mechanical load requires more mechanical structure.


Q: Are there any remarks regarding medium motor repair you would like to conclude with?

A: To ensure to a long-lasting motor and the most effective predictive maintenance, routine inspections, cleaning, vibration monitoring, and electrical testing are the best procedures.