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operational energy of a lighting scheme can be significant

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Corrosion can cause problems for HVAC systems so watch out for these red flags

When the lifts fail at train stations, airports or any public transportation facilities, the consequences can be severe, with passenger journeys being delayed or even rerouted.

So when we received notification of faults with three lifts at a Network Rail train station, we sought an evergreen solution. Stannah Lift Services maintains the lifts at all of Network Rail’s train stations across the UK. Recently, at the aforementioned station, there were several issues with the drive units in three lifts breaking down regularly and for no apparent reason.

Powering vertical motion

Variable voltage variable frequency (VVVF) lift drives are used to regulate motor speed and torque throughout a lift’s journey, so it draws far less current during acceleration and deceleration.

We noticed that the VVVF drive units on the three lifts were frequently breaking down, causing the elevator to stop working. The station became inaccessible for people with prams or any sort of restricted mobility.

When the drive unit was down, the lift could be non-functioning for one or two days, depending on the availability and size of the necessary replacement part. This caused inconveniences for passengers. We have all been in a situation where we couldn’t get off at our desired station and then had to resort to disembarking earlier or later and finding a new solution for the remainder of our journeys. It’s frustrating.

Whenever Network Rail reported the faults, we’d quickly repair the broken lift and not long after we’d get another report of a faulty lift. We didn’t think it was an incoming supply issue –rather, we believed the problem stemmed from the electrical power coming into the lift. Not our field of expertise, so we sought help from CP Automation.

The solution

Stannah requested monitoring equipment to check the quality of power going into the lifts. CP Automation responded with a Power Quality Study, which diagnosed voltage transients caused by the rail system power network as being the root cause of the drive failures.

Transients are brief but powerful highvoltage and high-current events that can last up to 100 microseconds. The resulting disruption can produce motor vibrations, noise and excessive heat, which lead to eventual drive failure and increased costs.

To help limit recurrent spikes and surges and the damages these cause, we equipped the lifts with three transient voltage surge suppression (TVSS) devices, which are specifically designed to protect sensitive equipment such as alternating current (AC) drives and variable frequency drives (VFDs). It’s an ideal solution for Network Rail station lifts.

With the devices fitted, it meant we could repair the elevators without the risk that transient voltages would cause any more breakdowns. Since the adjustments were made we have enjoyed months without this problem returning. The number of lift breakdowns has also reduced significantly, and transients are no longer causing routine disruptions.