Sunday, 24 March 2019
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Going up: Reducing downtime in elevators

Many of today’s elevator systems are experiencing mind-boggling lock ups and loss of programming.

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For elevator operation, poor power quality can cause recurring random failures, lockups and deprogramming of human machine interfaces (HMIs) on each floor. (Photo: © CP Automation)

John Mitchell, global sales & marketing director at supply, installation and repair specialist CP Automation, explains how elevator maintenance managers can prevent these annoying occurrences through improved power quality.

Elevators play a crucial role in human logistics and thus present a lucrative opportunity to improve the efficiency of buildings worldwide. Modern buildings are being erected to greater heights than ever before. As a result, newly implemented elevators are required to travel higher and faster than their predecessors. With these changes come a new set of problems and maintenance issues for engineers.

Change in fundamental frequency of power

To manage these new heights, today’s elevator software and hardware are more complex, and therefore more sensitive to fluctuations in power surges. This does not only refer to the strong surges from lightning strikes or utility companies, but also the transient surges that can happen thousands of times a day.

Transient surges are a change in fundamental frequency of power that can occur multiple times a day on the power supply network. These surges are a result of switching operations of inductive loads, such as air-conditioning units, transformers and lift motors.

Surges related to lift motors are most commonly linked with elevator power quality issues. If the lift motor is controlled by a variable frequency drive (VFD), the business may benefit from increased efficiency and reduced energy costs. However, this does not manage the low-level transient surges that can occur countless times a day, exaggerated by VFD usage.

False zero crossings

Transient surges can lead to false zero crossings of the sine wave — the instantaneous point at which there is no voltage present. In a sine wave, this normally occurs twice during each cycle. Devices can be falsely triggered because of fast changing signals caused by transients, as they believe the zero point has been crossed, even when it hasn’t. It can cause confusion for all equipment on the grid.

Whether it is caused by transients or a freak utility power surge, insufficient power quality is destroying many elevators and their related equipment. For elevator operation, this can cause recurring random failures, lockups and deprogramming of human machine interfaces (HMIs) on each floor. However, this downtime and maintenance can be eliminated if the right protection is in place.

SineTamer cascade system

Typical surge protection devices are unable to prevent these issues as they are voltage triggered only. This means built in surge protection systems are not a feasible option. The answer to this problem is using a SineTamer cascade system.

This system offers much more than a standard surge protection device. It is an engineered transient disturbance filter, designed to monitor all 360 degrees of the sine wave. Using 360-degree monitoring, the SineTamer can prevent issues caused by false zero crossings of the sine wave.

Results from the field

In Central America, one business was faced with a major utility generated power surge, destroying several elevators and related equipment in its facility. Yet, right next door, being fed from the same transformer, not a single elevator component was damaged. When investigated, the foreman of the unaffected building explained they had installed SineTamer.

Over in South America, the Montevideo World Trade Centre contained 30 elevator systems, routinely experiencing 5-7 issues daily. In addition to those were the constant deprogramming failure of HMI’s on each of the 22 floors. Upon installation of the SineTamer®, all failures, lockups and loss of programming ceased by 100 per cent.

The planet boasts huge numbers of elevators in operation today as the industry takes on significant growth. As worldwide construction of tall buildings continues to increase, improving management of transient surges will mean that new and old elevators will now have a fairer chance in lasting the test of time — without costly maintenance issues.

John Mitchell

www.cpaltd.net

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