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Hoist Extended Speed Control

Zip-Moving™ & Multi-Zip-Movement™ Explained

With more than a decade and a half of applications behind it PE® Micro-Speed® Multi-Vector® with Zip-Technology® for hoist speed control has proven to extremely reliable and robust and precise. Use of Zip-Technology™ features have become more and more popular. Zip-Up™ and Zip-Down™ adjustments allow for variation of the extended speed by adapting hoisting load and torque requirements. This allows increased speed (above base speed) for the loads involved up to hoist manufacturers recommendations and any practical mechanical limits.

Zip-Moving™ – How easy can it be!

Setting parameters C120-C129 has proven to be the easiest and most flexible way to run at extended speed (above the motor “base” speed). Since the Multi-Vector® Drive, using Zip-Technology™, adjusts motor speed based on motor torque and the load’s torque requirements; it maximizes performance and cycle times for you. A lightly loaded hoist can then be lifted or lowered at a faster rate and much more reliably than other methods. Setup entails turning Zip-Up and/or Zip-Down features on (C120-C129). Selecting the max load-torque percent allowable for Zip- Move™ is the next step. Last, select the target threshold speed (open up the limits in parameters CL6 & CL7- see manual). The dwell time is also adjustable. It is important to verify and check motor and gearing RPM ratings and also adjust limit switches to accommodate higher hoist speeds. Always verify that settings will not exceed manufacturer’s specifications of the equipment or create a safety concern (high speeds at light loads may not be advisable in some applications for example).

Can be used on Tandem hoists too!

Multi-Zip-Move – Used on multiple hoist applications with Page-Swap™:
When setting up a dual hoist, proprietary Page-Swap™ is used (“super programming” available on all PE® Multi-Vector® drives) is used to “make decisions” and set fixed speeds for both hooks while the VFD’s are operating, instantly. This allows and maintains exact speed matching – regardless of the load on either hook. The setup is easy. Page-Swap™ help and setup is just a phone call away to PE® customer technical help-line.

Since the Zip-Technology™ functions can limit the speed based on load; any non-balanced load has the potential to create a speed difference during extended speed operation. Answer to these applications is the use of Page-Swap™ to make the decision of when to allow extended speed to operate. This is the beauty of PAGE-SWAP™ – only available in PE® equipment. Super –programming which changes the drive characteristics UNDER SPECIFIC CONDITIONS, and “swaps” them in REAL TIME while the drive is operating. On Multi-hoist ZIP-Movement™ a compromise between maximum load size and maximum speed is necessary. Simply, the heavier the load you allow to run at extended speed, the lower your max speed (above base speed) setting must be. With Page-Swap™ this is accurately and easily accomplished.

These features should only be used on a non-load brake style hoist. Hoist manufacturers usually do not allow running a load brake hoist above rated speed. At any speed below base speed, one can only lift up to the rated capacity of the hoist/crane. One should not lift more than the rated capacity of the hoist/crane regardless of what speed the hoist is running. The exception may be during a load test. Contact PE® Technical group for application programming assistance if needed.

© Power Electronics® International, Inc. 2011

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Why use encoders on no load brake hoists?

Why “Sensorless Vector” drives are being misapplied in the crane industry?

Power Electronics® International, Inc. has over 40 years in the manufacturing, engineering and design of a.c. drives for overhead hoist and cranes. Previous to this the President and founder of the company, Victor J. Habisohn, was project manager of General Time Corporation with the responsibility of the design of the Timing System used in the Apollo program. Equipment supplied was to be of the highest reliability since it triggered all other functions in the spacecraft – quality, reliability and safety were extremely important. This philosophy has continued in all PE’s products lines. Safety and Reliability is of the utmost importance.

Given the above, it is understandable that PE® would take great pains to understand all the safety concerns inherent in overhead hoist and crane electronic control. And indeed the ramifications of a “failure” of any part of the electrical system become more and more obvious as one understands the system “from the inside out”. Small electronic components, some no larger than a small coin can, in many cases, are the only safety link available between a safely running hoist or crane and one “out of control”. Redundant safety circuitry must be applied so that if one fails the other “takes over”.

In most, if not all, “general purpose” variable speed drives, safety is designed into the drive for “standard” applications such as conveyor use, simple speed control of pumps and fans etc. Failure of a component could simply stop the equipment and not allow it to run properly or to run erratically. With a hoist drive, a failure in certain circuits becomes catastrophic in the sense that even though the equipment may not function properly and may not become
damaged, the hoist “holding brake” could be told to “open” with insufficient torque or energy to “hold” the load i.e., load drop.

Sensorless Vector drives are designed for systems that don’t require an encoder. By understanding the a.c. motor and creating a “model” of its electrical characteristics, the sensorless drive can “estimate” motor speed and position. Under various conditions the estimates and internal sensors “fail” and the hoist can be told to operate within a range or parameters that are unsafe. The questions then arises of the frequency of failure and what kinds of failures can the user of the equipment accept.

On a conveyor or CNC equipment, the loss of a product or erratic control of the conveyor is not catastrophic, and may even not be very noticeable. On a hoist, failure or “imprecision” because of an “estimate” can become catastrophic—i.e., load drop etc. Extreme destruction, death of individuals, damage to crane structure can be the result.

Power Electronics® International, Inc. in studying all the ramifications and safety concerns decided that so-called “Sensorless” Vector technology should not be used on hoists without mechanical load brakes. Sensorless Vector technology is attractive to some because of the perception that it makes a physical encoder unnecessary on the hoist or hoist motor thus decreasing system cost. Nothing could be further from the truth, an encoder is necessary to
eliminate the “guesswork” and have 100% assurance of hoist speed and position (not a guess, relying on “motor models”). Safety is the prime reason to use the encoder; a mathematical somewhat blind “guess” is not sufficient in hoisting and heavy equipment, heavy industrial environment where a “failure” can mean a disaster.

Power Electronics® International, Inc. as one of the industry’s leading corporations involved in the design of a.c. drives for hoists and does not feel that Sensorless Vector drives have any place in no load brake hoist control. (A “load brake” being a device which, separate from the “holding brake” will physically stop the hoist from falling by means of a mechanical “internal” ratcheting or other type of resistance which must be “overcome” in the down direction).

Sensorless Vector drives can be misapplied very easily because of the extensive “marketing” of the technology to other non-crane industries. Even some “engineers” have made the serious mistake of not recognizing the inherent problems, mostly due to overzealous drive salesmen who “oversell” their products features and have little to no real knowledge of the safety aspects which need to be addressed. Often even a group of engineers who approve the
drives for “hoist” use have never looked closely at the areas of failure (and aging failure modes), which can occur with a hoist “fighting gravity”, and at “Zero-speed”. Zero and very low speeds are particularly dangerous points which sensorless vector drives have accuracy problems. On a conveyor or other horizontal types of equipment zero and very low speeds are not usually problematic.

On a hoist it is another story. A hoist’s brake opens at zero speed and gravity takes over! Not an application for Sensorless systems. Zero tolerance of a brake opening at the wrong time must be the standard in the hoist-crane industry. A motor encoder is necessary to help with this safety need. The possibility of failure of internal drive circuitry is also reason enough for using an external encoder as a check on the drive function. It must also be understood that there are many other safety concerns, besides the use of an encoder, which must also be addressed in an electronic hoist drive – these are not covered in this paper.

In addition, use of multiple motors either in tandem or switching between one or another is not possible with sensorless drives since the exact motor parameters are required for the internal “motor model” which is for one motor only. Motor parameters also change with temperature and other variables. An encoder solves many safety and reliability problems by giving the drive direct and absolute feedback so it can react to any changes. Power Electronics® International, Inc. is the only company in the world, which designs hoist and crane electronic a.c. drives specifically for those applications. All others are simply relabeled or re-programmed general purpose drives. All drives are simply NOT the same. If it’s not a PE® drive it is not crane-hoist designed. Ask for PE® equipment from your crane dealer or crane service company – they are readily available. This short note is not meant to be a thorough scientific analysis, but is a simple to help point out why encoders are important on an a.c. overhead “no-load brake hoist” using electronic speed control. The above information is meant to be a short beginners explanation. For more specific information call us at 1-847-428-9494.

© Copyright 2005 Power Electronics® International, Inc.

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Dam fine job!

Two firms teamed up for the upgrade of historic cranes at the Bagnell Dam, in the picturesque Lake of the Ozarks region, Missouri

Located about three-and-a-half hours southwest of St. Louis, the Bagnell Dam was built over a two-year period between 1929 and 1930 by Union Electric Light &Power Company (now known as AmerenUE). When completed, it formed the beautiful area known as the Lake of the Ozarks region, Missouri.

As part of the original plant equipment, Whiting Corporation was contracted to supply all of the plant’s overhead gantry cranes. These cranes, including two 7M capacity head gate cranes, as well as the 150t capacity power house crane, are primarily used to perform maintenance and removal/replacement of major plant equipment. The two head gate cranes service 24 spill gates that assist in controlling lake levels. Periodically, each of  these gates must be raised for various maintenance activities.

Although the crane controls were still in excellent condition, upon review of the new and more stringent Federal Emergency Management Agency (FEMA) requirements under the National Dam Safety Program, AmerenUE elected to upgrade the existing controls. In August 2007, Whiting Corporation was favored with the contract for this work, with Whiting Services, Inc. and Power Electronics® International, Inc. performing on site work and project management.

A key FEMA requirement of the new control system specified precise torque limiting capability of the hoist motion to help prevent damage to any of the spill gates as they are raised. These gates can remain in place for some time and it is not uncommon for them to “stick” in place. Therefore, uncontrolled lifting torque during hoisting can (and had at another hydro plant) literally snap the gate pivot bearing and distort the gate structure.

Another key FEMA requirement called for an onboard, propane-supplied, 40kW back-up generator capable of transferring power to either head gate crane in the event of loss of plant power. Installing the generatar in the crane’s control room was no small task. The plant and cranes are registered with the Historical Landmarks Society, which meant removing and replacing two large sections of original casement style windows to place the unit out of sight so that the appearance of the cranes was not altered.

To meet these control requirements, Whiting Services selected Power Electronics® International Inc. (PE) as its supplier for the new motor and control system. The hoist motions were converted to PE’s Micro-Speed® Multi-Vector® drives and the bridge and trolley motions employed Micro-Speed® open loop drives. Together, these drives provided infinitely variable speed and lifting control of the load while also achieving all of the  torque limiting requirements to meet the plant’s expectations.

Other safety and control system upgrades included: radio/cab modes that allow either single or dual motion functions; an anemometer (wind gage) alarm system; anticollision, hard-wired festoons; various safety status lights and horns; ground level emergency stop stations; cab lighting and heating; and new 1,000 watt metal halide area lights for night time work activities. Because of the success of the head gate crane upgrade, in June 2008 Whiting and Power Electronics® International, Inc. were awarded with a contract to perform a similar upgrade to the 15M power house crane. This upgrade also included an engineering study to allow for an engineered lift of approximately 16M to replace a turbine assembly.

Whiting Corporation and Whiting Services were able to review the original circa 1930s engineering drawings and calculations to provide viable, effective, long-term solutions. Other enhancements included: eliminating the original single motor bridge drive with over 80 feet of line shafts; bevel reducers; and support bearings in favour of compact, twin drive motor reducers located at the wheels. These enhancements increase the effective life of the bronze bushings and shafts to further reduce long-term maintenance costs.

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PE® controls are used at Bruce Power

Lifting power

Written by Richard Howes, OCH Magazine

With 85 cranes and over 750 hoists on site, the crane guys at North America’s largest nuclear power site have their work cut out.

Pete Richards, multi-trade team leader, crane crew, and Fred Wolsey, system engineer, cranes and hoists, are responsible for the safe operation and upkeep of all the lifting equipment at Bruce Power, Canada’s first private nuclear generating company and the source of more than 20% of Ontario’s electricity. The facility is located approximately 250km northwest of Toronto.

On a day in mid-May this year, Bruce Power’s Unit 5 was in a ‘shutdown’ state for regular maintenance. The unit which usually generates about 890 megawatts of electrical power had the focus of numerous workgroups. Replacing the energy supplied by such a unit is of substantial value to the company and its stakeholders.

The crane crew, which consists of a team of six electrical and eight mechanical technicians, was working elsewhere on site at the spent fuel bay at the Bruce ‘A’ station where a newly installed Canadian Overhead Handling Inc. 100 ton crane, with 80ft span, was being inspected.

This crane has a technical positioning system which allows movement of the load (highly radioactive spent fuel) only within confined coordinates. The spent fuel is encased in a shielding flask which protects the workers and environment from any external dose. It weighs close to the full capacity of the 100 ton crane.

Having completed work at the spent fuel bay, the crew found themselves in transit to the ‘B’ station, where a crane in the reactor vault had ceased to function in one direction during the ‘shutdown’ phase. The cranes at Unit 4 of the ‘B’ station have been in operation since commissioning almost 30 years ago. In the hot, highly radioactive environment, insulating material and plastics deteriorate at a higher rate than in conventional systems.

The electrical technicians of the crane crew have acquired experience and skills to enable them to expeditiously locate the “gremlins,” as the crane guys put it, which in this case invaded the control circuits of the vault crane. With this problem solved, detailed work reports and system weaknesses identified, the crew returned to the day’s original activities.

Having regular inspections by qualified and knowledgeable staff has ensured safe operation of these cranes over many years. It has become apparent, however, that in order to maximize efficiency and minimize downtime and radiation dose exposure to the crane crews, the cranes in each of the Bruce Power ‘B’ plant units will need to be replaced. Planning is now underway to begin replacement of the first unit’s cranes in the Spring 2009.

The commitment to replace the eight vault cranes (two cranes per unit), with 10.5 ton capacity Yale units with 60ft spans, has been accepted by the crane crew who will help design, build, install and commission the cranes. Ultimately, the crew will have intimate knowledge of the working of the new cranes which will help provide safe, reliable operation, crucial to the activities associated with shutdown maintenance.

The crane maintenance program at Bruce Power is recognized as an Industry Best Practice by the Electric Power Research Institute (EPRI).