Repaired, refurbished or new?

Frequency converters often become defective after a few years and have to be replaced. Apart from buying new, repair is also possible. What has to be borne in mind in this regard.

By Patrizio Fontanarosa

In modern lifts, the motor and frequency converter constitute a mutually coordinated functional unit to facilitate optimal travel operations. Gentle starting, braking and acceleration are the basic functions of the frequency converter and make a considerable contribution to a smooth lift trip.

A frequency converter consists of complex power electronics that wear out over time. Their proper functioning is then no longer guaranteed. Consequently, frequency converters often become defective after a few years and have to be replaced. This usually results in unexpected costs for replacement and successor models, especially if the identical frequency converter is no longer produced and has to be replaced by new models. Extensive switching changes then have to be made to the controller. These frequency converters may also have been discontinued by the particular manufacturers and replaced by new models. Installation of a repaired device is then an alternative.

But care must be taken since only those frequency converters with a complete refurbish offer safety and durability, which ideally should have been carried out in a monitored or certified workshop. In my view, the annual check of the production process should normally be carried out by an authorised inspection body.

All wearing parts replaced

Technician working on a Variodyn 30. Photo: © FLP Lift Parts

What does refurbish mean? In the event of an refurbish, the frequency converter is disassembled, professionally cleaned and all wearing parts (relays, capacitors, etc.) renewed and replaced. The frequency converter is restored to a condition like new to guarantee safety and durability. The refurbished frequency converter is issued with a two-year guarantee, just like a new device.

What is the decisive difference from simple repair or reconditioning? In the case of simple repair or reconditioning, only defective components are replaced while other components in the frequency converter are not touched. By contrast, in the case of a complete refurbish, all wearing parts are replaced. The frequency converter is restored to a condition like new.

Different costs and prices

Due to the much higher expense, the two versions differ markedly in cost and as a result in price. Caution is advised here since there is no standard definition of the term "refurbish": What for one is an overhaul is for others a simple reconditioning. But in our experience, in the case of devices that have not been completely refurbished, the risk for renewed failures increases for operators and the safety of lift users cannot be guaranteed either.

Why can old, refurbished frequency converters be more durable than new successor models? Today, components are frequently smaller in size for cost reasons than earlier. But this can also shorten the service life of frequency converters.

Environmentally-friendly process

Technicians carry out static measurements on the ThyssenKrupp CPI26E. Photo: © FLP Lift Parts

Refurbish is also becoming increasingly popular for companies interested in combatting the current climate crisis. It makes it possible to reduce waste and environmental pollution. Refurbish is not just an environmentally-friendly process but also permits reuse of products that do not end up in waste and as a result support recycling.

The author is a qualified engineer and owner of FLP Lift Parts GmbH, which is specialised in the overhauling of frequency converters. The company recently underwent certification by TÜV Süd and is monitored by it annually.

More information: elevator-electronics.com