Faced with the need to protect critical operations from utility power interruptions and other power-quality problems, Danny Woodbeck, maintenance supervisor at Canadian National Railway’s Symington Yard in Winnipeg, MB, took an unconventional approach. Working closely with Meridium Power, he harnessed the energy from a low-speed flywheel in an innovative motor-generator set developed by Precise Power Corp. to power his way through momentary power interruptions and other power-quality concerns.

The electro-mechanical system provides protection similar to that of a double-rectified, battery-based power protection system, producing an output with a constant frequency and regulated voltage for critical loads. The system uses stored energy from the integral low-speed flywheel to ride-through momentary power interruptions, eliminating the need for large battery-banks with their high maintenance and replacement costs. Keeping a lid on costs is an important consideration for Woodbeck as his company strives to compete in the competitive North American transportation market.

This system has eliminated power interruptions to the rail yard’s communications equipment and humping and intermodal operations, which previously caused major disruptions in shipping schedules. Woodbeck points out that any delays at the yard can quickly ripple throughout the entire rail network, costing the railroad thousands of dollars in penalties for late deliveries. At the same time, this innovative approach saves Canadian National money by eliminating the infrastructure and maintenance requirements of the large battery banks used in conventional systems.

The Need for Protection
Symington Yard, one of the largest humping switch yards in North America, is a major hub for Canadian National’s domestic east-west traffic and trains headed to and from the United States. Here, cars from arriving trains are uncoupled and re-assembled into outbound trains headed for a variety of destinations. With about 130 miles of side-by-side tracks covering the 650-acre site, the yard has a capacity of 4,300 railcars at one time and processes about 2,000 cars a day around the clock.

In addition to switching activities, the yard also features large shops for maintaining diesel-electric locomotives, railcars and electronic equipment, a weigh facility, and a general maintenance facility. An extensive customer-owned distribution system services the yard, providing electrical power to operations across the expansive yard.

Railcar Humping
The most striking feature of Symington Yard is the humping operation where radio-controlled locomotives push a train of railcars to the top of a rise, where each car is released down a gently sloping track. Gravity then takes over and carries the cars though a series of computer-controlled track switches and rail-mounted wheel retarders that control the speed of each car and direct it to the appropriate track where it gently couples with a preceding car to form a new train.

Minor glitches and momentary interruptions in the utility supply to the humping operation pose a serious threat to these activities. Migrating Canada geese in the spring and fall that feed on grain in the yard are a major problem. When startled, these large birds often fly into power transmission lines, creating phase-to-phase faults that cause disruptive power outages.

For years, the yard’s operations went unprotected from power interruptions causing frequent downtime and service disruptions. Battery-based equipment used to protect the computer system monitoring the operations was expensive to maintain and required frequent battery replacements. Batteries generally used in this type of application last no more than five to 10 years and replacement can represent up to half the cost of installing such a system.

By the fall of 2001, the entire battery backup system had reached the end of its useful life and had to be replaced.

Communications
Earlier that year, Canadian National commissioned a new communications center at Symington Yard, which serves as the main hub for Winnipeg-based communications. The center is the primary fiber hub for railroad’s Prairie Region, routing communications for most areas of the company’s operations. They include Canadian National’s call center located in Winnipeg, intermodal operations, rail-yard communications and switching, inter-satellite yards, and the centralized traffic control system that controls and monitors track signals across the Prairie Region. This vital facility requires high-quality, reliable power to prevent any interruptions that immediately impact the company’s operations across North America.

Intermodal Operations
Canadian National relocated its Winnipeg Intermodal Terminal to Symington Yard in the fall of 2004. The facility manages the transfer of shipping containers between Canadian National’s large rail system and highway trucks responsible for local delivery and pickup from a large network of customers. Maintaining tight shipping schedules requires the ability to continue loading and unloading as many as 400 trucks a day during all types of weather conditions. Power interruptions caused by wind or ice storms could cause major interruptions to rail operations if intermodal activities were left unprotected.

Critical operations at the intermodal terminal include a large computer bank that tracks incoming containers, providing storage locations, and shipping schedules for output containers. The facility must be capable of processing inbound and outbound trucks on a continuous basis to optimize flow through the facility, which is constantly loading and unloading containers from railcars and highway trucks.

Clean, Battery-Free Power
As the maintenance supervisor, Woodbeck is responsible for maintaining reliable power at the rail yard. Having worked closely with Manitoba Hydro to install a distributed network for monitoring the customer-owned distribution system that carries electrical power throughout the yard, he turned to the electrical utility when he began his search for a solution to power reliability problems the yard was experiencing. After in-depth research and detailed consultations with Manitoba Hydro, Woodbeck selected the Roesel Motor-Generator (RMG), developed and patented by Precise Power Corp. of Palmetto, FL, as his preferred solution.

The three Written-Pole RMG power protection systems at Symington Yard were designed and installed by Meridium Power. The company is a wholly owned subsidiary of Manitoba Hydro, Canada’s fourth largest electric utility, which obtained the exclusive commercial rights to Written-Pole technology for the Canadian market. Meridium Power worked closely with Precise Power Corp. to develop a family of products based on the technology. The subsidiary is responsible for Canadian sales and service, working closely with suppliers of electrical equipment and standby generators in order to provide optimal solutions for its customers.

The RMG operates as an AC permanent magnet motor-generator while on utility power. The motor drives the generator mechanically and the electrically isolated generator provides a separately derived source of continuous, clean electrical power for critical equipment. The unit is designed to ride through the majority of utility blinkouts or dips and absorb transient spikes and power surges, explains Dale Friesen, P.E., general manager of Meridium Power.

“The RMG offers a reliable form of energy storage with much lower maintenance and infrastructure requirements than conventional, battery-based power protection alternatives,” he says. “It is configured to provide electrical isolation, power conditioning, and momentary interruption protection in a single footprint. The integrated, low-speed flywheel provides extended ride-through coverage for more than 98% of all utility interruptions, eliminating nuisance starts of standby generation equipment.”

During a ride-through operation, inertial energy from the flywheel drives the generator, which delivers a voltage-regulated, constant frequency output for more than 10 seconds at rated load. “That’s more than enough time to start a standby power source, such as a diesel generator, without any break in power to critical equipment,” Friesen says.

“Once operating, the standby generator provides power to the RMG, which maintains an isolated output. This no-break approach prevents damage to critical equipment by faults and transients in switching equipment. The Caterpillar diesel-standby generators selected by Meridium Power for these applications were sized to support both critical and semi-critical loads during prolonged utility outages.”

Friesen reports that the RMG has been used to protect equipment and prevent shutdowns in applications ranging from broadcast and cable television transmission, to weather and aviation radar sites, to factories and hospitals. “It’s been used with sensitive loads as computers, security systems, process equipment, medical devices, controls, and instruments,” he says. “The design also prevents load harmonics from critical power electronics equipment from feeding back into building wires and utility systems through complete electrical isolation.”

Written-Pole Technology
The key to the performance and efficiency of the RMG is Written-Pole technology, developed and patented by the manufacturer, Precise Power Corp. It is used in both the motor and the generator.

Conventional electric generators have a fixed number of magnetic north and south pole sets, dictated by the rated speed of the machine. As Friesen notes, this relationship is fixed into the construction of the machine. These pole sets interact with the rotating fields produced by the stator windings to generate electricity at a certain frequency for a given rotor speed. By contrast, Written-Pole technology allows the magnetic pole pattern on the magnet layer or rotor to be re-written or re-magnetized, changing the polarity and span of the magnetic poles as the generator is rotating. As a result, Written-Pole motors and generators are not constrained by either a fixed set of magnetic poles or an even number of poles.

“This opens up a window of opportunity not available with conventional motor-generator designs,” Friesen says. “The concept does not contravene any of the scientific principles that govern the operation of electric machines, but it does break free from conventional wisdom that assumes a linear relationship between rotor speed and output frequency.”

Written-Pole technology makes it possible to match the number of magnetic poles on the rotor to the speed, allowing the Written-Pole generator to maintain a constant frequency output over a considerable speed range. As a result, changes in generator speed resulting from momentary outages and voltage sags or surges can be compensated for, maintaining a constant 60-Hz output.

This same technology is used in the RMG drive motor to produce optimum starting torque and high operating efficiency with very low starting demands, Friesen notes. It allows for a low per-unit starting-current–to-horsepower ratio that is typically less than three times the rated full-load current of the unit, which greatly reduces voltage sags in the line during starting.

“The copper in–copper out construction used in Written-Pole power protection systems is a proven concept similar to that used in premium grade electric motors and generators ensuring a long life and resistance to damage from sags, surges, and transients,” he says.

Written-Pole technology has also been used to develop the world’s largest single-phase motors, with ratings up to 100 horsepower available for operation on rural single-phase distribution systems, Friesen adds. “This eliminates the need for three-phase power for applications, such as irrigation pumps, grain dryers, and oil wells,” he says.

How It Works
The RMG features a proprietary AC permanent magnet motor-generator with an integral low-speed, high-strength ductile iron flywheel. “The innovative external rotor construction allows the flywheel to be incorporated directly into the rotor of the motor-generator, eliminating the need for additional bearings and couplings, enhancing reliability and serviceability,” Friesen says.

“Written-Pole technology eliminates the need for high-power electronic devices to convert and regulate the generator’s output frequency and voltage. It controls the output voltage and frequency at the rotor without rotating field windings. That makes the design the only power protection device on the market that can maintain a constant frequency output over a considerable speed range without external power conversion.”

The three-phase motor and three-phase generator are integrated into a common frame and coupled by a shaft and integral flywheel, which operates at either 1,800 rpm or 3,600 rpm on a 60-Hz distribution system, depending on design and application of the machine. It’s available in four models—35 kVA, 40 kVA, 50 kVA, and 60 kVA—to match the size of the load. Units may be operated in parallel to provide redundancy or accommodate larger installations.

In steady state operation, utility power powers the motor that drives the generator to provide clean isolated power for critical applications. The generator output is isolated electrically from utility supply. “This creates an impenetrable barrier between the protected equipment and utility to prevent damaging power-quality events and harmonic transmissions from passing between the two,” Friesen says.

The RMG enters its ride-through mode when utility power is interrupted, drawing energy from the flywheel to maintain operation of the generator, which continues to provide a constant frequency and voltage output for the critical load. For applications where prolonged outage protection is required, the unit works together with a standby power source, such as a diesel generator. After a suitable delay of approximately three to five seconds, a signal is sent to the standby power source, initiating a startup so that standby power is available, if the outage extends into a longer-term interruption.

“Once utility power returns, the motor-generator resumes operation and rapidly restores the flywheel to its rated speed to prepare the unit for the next interruption,” Friesen says. “The low-speed design allows for significantly shorter recovery times—20 seconds or less—than comparable high-speed designs. This ensures adequate coverage is maintained during frequent interruptions.”

An enhanced version of the RMG, the RMGi, features a three-phase motor-generator coupled with an integral standby engine in a single footprint to cover all aspects of power protection from voltage sags and surges to prolonged power outages. In this case, the stored energy in the unit’s flywheel, instead of a cranking battery, is used to crank the standby engine. This design eliminates the need for separate standby generators, transfer switches, interconnecting electrical distribution, and battery chargers.

“If a utility power outages lasts more than six to eight seconds, it’s likely to become an extended outage,” Friesen says. “With the RMGi, the electrically operated clutch closes and flywheel energy cranks the standby engine. Replacing the cranking battery with flywheel energy eliminates a major point of failure in conventional standby generators. About half of all these failures result from improperly maintained or improperly charged batteries. Once started, the engine continues to power the motor-generator until utility power returns. Then, the clutch opens and utility power resumes driving the RMGi.”

System Comparisons
Friesen notes some of the ways the RMG systems are paying off for the Symington Yard operations.

• Fewer momentary interruptions—At the loss of utility power, most conventional motor-generator sets can maintain a frequency and voltage output within an acceptable range for no more than a second. Often, that’s not long enough to prevent costly downtime. “In the case of a fiber optic manufacturing plant, a power outage of just 100 milliseconds can ruin an entire reel of cable,” Friesen says.
  
  Precise Power Corp.’s design extends this ride-through to more than 10 seconds at full load and to as much as 45 seconds at low load levels. “About 95% of all utility outages on the North America power grid last less than three seconds and 98% to 99% last less than 10 seconds,” he says. “That means less than 2% of all outages experienced by a typical industrial customer last longer than 10 seconds.” The reliability problems faced by Canadian National illustrate this. Numerous short-duration outages resulting from breaker operations related to faults from wildlife contacts and severe weather were disrupting operations.
  
  The Written-Pole RMG is perfectly suited for this application, explains Woodbeck. “Its extended ride-through capabilities enable the system to protect against most outages at the yard without starting the standby generator,” he says.
  
• Higher-quality power—The RMG operates as a separately derived power source generating a new sine-wave that is in phase with the utility supply, Friesen explains. A standard online UPS uses a rectifier to covert utility power to DC power. This power, in turn, is fed to an inverter that uses electronic switches to manufacturer a simulated sine wave. However, even the best of these simulations can introduce harmonics or spikes onto the output waveform and often require filtering equipment to overcome these problems. As a result, he says, the useful life of the sensitive electronics can be impacted.
  
  Offline and line-parallel or line-interactive UPS systems that use inverters and ferroresonant transformers rely on filtering to prevent transients on the utility systems from affecting critical equipment. These systems can allow high-voltage spikes to pass through to electronics and introduce turn-on and/or switching interruptions and transients as they assume the load. While this may not crash a system, it can stress electronics, Friesen notes.
  
  “Many devices are also frequency sensitive. Conventional motor-generators operate between 59 and 60 hertz at steady state. However, even those with large flywheels will experience frequency decay that will drive the output out of specification in as little as several hundred milliseconds when the utility power is interrupted.”
  
• Lower infrastructure costs—Because the RMG requires no external battery banks to provide energy during outages, it has a relatively small footprint. That, Friesen points out, gives it another big advantage over a conventional UPS, which includes a bank of batteries and inverters that require air-conditioning and ventilated, secure space.
  
  “Battery-based UPS systems were originally designed to protect computers, which need a clean, temperature-conditioned environment to function adequately,” he says. “As a result, these systems seemed to adopt many of the same requirements as the computers they were designed to protect.”
  
  Providing the space and proper facilities that meet building codes for such a system in an industrial application can be difficult and expensive. The compact, robust RMG package is much simpler to install and much more compatible with industrial sites having the same tolerance for ambient conditions as a conventional electric motor or generator. This was an important consideration for Canadian National since space availability at each installation site is limited.
  
  “The RMG can operate in the same environment as an electric motor, making it compatible with the shop floor in most manufacturing plants,” Friesen says. “It is suitable for installation in ambient temperatures ranging from 32 to 122 degrees Fahrenheit [0 to 50 degrees Celsius]. Meridium Power has provided systems for operation in colder ambient temperatures by using outdoor enclosures that capture the heat of the unit in order to maintain the proper enclosed temperature without a heater.”
  
• Lower maintenance costs—Battery-based UPS systems require regular checks and maintenance, whether cleaning and re-tightening terminals on maintenance-free batteries or checking acidity and fluid levels of lead-acid batteries to keep them in top operating condition. Recharging a battery may take 24 to 72 hours, although more sophisticated chargers can reduce that time to around four hours at some cost to battery longevity. However, the RMG recharges in less than a minute.
  
  Also, because batteries lose their effectiveness after repeated discharge cycles, they often have to be replaced well before their anticipated life has expired, Friesen says. Like standard motor-generator sets, the RMG requires only semi-annual or annual maintenance. In the case of Symington Yard, this service is provided by Meridium Power, freeing Canadian National’s maintenance staff for other operations.
  
  The RMG provides consistent performance over a wide range of ambient temperatures and is not affected by the dust, dirt, and grime, which can corrode battery terminals. The primary maintenance item is the bearings. However, Friesen reports, the low-speed flywheel increases bearing life, compared to high-speed flywheel designs, and reduces the complexity of installing bearings, which are designed to last about four or five years. Bearing replacement costs a small fraction of a set of batteries, he adds.
  
• Longer diesel generator life—In installations where downtime is costly, standby generator sets are often started the instant power is lost to minimize the duration and impact of power interruptions. Some operations even start engine-generators during bad weather in anticipation of a power outage. This can result in a high number of unnecessary engine starts and extended operating hours.
  
  The RMG installations at Symington Yard are used to bridge the gap between the utility outage and the time that the standby diesel generators are online and available. By allowing Woodbeck to delay starting of the standby units, the system’s extended ride-through reduces wear and tear on the engines and transfer switches. Extending the life of standby equipment reduces maintenance and replacement costs and improves profits at Canadian National,” Woodbeck says.
  
• More savings—The RMG uses a synchronous motor which has, in essence, a unity power factor to the utility. That can cut electrical costs, if the utility charges extra for a lower power factor, Friesen points out. What’s more, unlike inverters, rectifiers, and UPS devices, which can pollute utility lines, harmonic feedback from the RMG is extremely low. This reduces concern over interaction with other loads at the customer’s location. Since the output is isolated from the utility and other loads within the customer’s facility, harmonics generated by the protected load can’t feed back and disrupt operation of any nearby electronic devices.
  
  “The low level of current harmonics generated by the RMG, combined with the ability to restart immediately once utility power is restored without overloading the supply distribution, makes it much easier to integrate standby generators in this power protection system,” Friesen says. “This also allows the use of simpler, lower-cost transfer switches to reduce the complexity and cost of installation.”
  
• Utility-friendly—High operating efficiency reduces operating costs, while low starting demands reduce voltage flicker. A Written-Pole motor-generator requires less than half the startup current of a conventional motor, Friesen notes. Many solid state devices, such as inverters, must be oversized to handle pulse loads such as radar equipment. “Because of the greater tolerance of Written-Pole technology and the immediate availability of stored-energy in the flywheel, a 35-kilovolt-amp unit can usually handle the same pulse loads as significantly larger solid-state inverters,” he says.

A Turnkey Package
The power protection systems installed at Symington Yard feature a 35-kVA RMG package. It includes electrical contactors, automatic bypass system, electronic controls, and safety devices. A Caterpillar diesel standby generator, rated between 150 kW and 230 kW, was installed at each site depending on the semi-critical load requirement. Customer service operations were the first to receive a system, which Meridium Power installed in the summer of 2001. A few months later, the company installed the second system at the humping operation. The third system was installed this past fall (2005) at the intermodal facility.

In each case, the installation was managed to minimize disruption to yard operations. Meridium Power assembled the entire system—the RMG, standby diesel generator along with fuel storage, transfer generator, and interface equipment—offsite in a pre-fabricated structure. The work was performed in close cooperation with Toromont Caterpillar, a major distributor for Caterpillar in Canada. This prepackaged unit was then tested and transported to the yard, where it was interconnected to the electrical distribution system at each of the locations. Physical downtime during each installation was less than two hours.

“Since the RMG systems were installed, the number of power outages at Symington Yard has remained about the same,” Woodbeck says. “However, their impact on operations has been all but eliminated.”

GREG NORTHCUTT writes frequently on business and construction issues.

DE - May/June 2006