How hard can it be to specify variable speed drives for HVAC applications?

From over two decades of in-house and marketplace experience, ABB Drives has identified the top thirty technical challenges facing users of variable-speed drives (VSD) within the building services sector. To varying degrees, the challenges affect consultants, OEMs, systems houses, facility managers and end-users.

The issues are based on feedback from customers, observations of third-party installations and changes to legislations, regulations and standards. The aim is to identify the challenges relevant to each segment and publish an e-book of the options available for overcoming them, without re-inventing the wheel

New motors types

According to ABB Drives, many written specifications have not kept pace with changes to the hardware and software in modern drives, or the differences from one manufacturer’s product to another. For instance, today’s heating, ventilation and air conditioning (HVAC) installation will use a variety of motor types from electronically commutated motors (ECMs), permanent magnet motors (PM), synchronous reluctance motors (SynRM) and induction motors. Yet users need to be extremely careful when selecting which type of motor can be used for their application.

At low powers ECM motors offer some efficiencies, but above 11 kW, they are too big to fit fans. Also at higher powers, heat losses cannot be easily dissipated within a fan’s hub design. By contrast, using a VSD and motor package in these higher powers avoids these issues and brings a host of other important benefits such as harmonic mitigation, the ability to catch a spinning load etc.

The cost-effective SynRM controlled properly in a well-designed system can achieve the specific fan powers when controlled by a traditional VSD, bringing advantages such as: improved harmonic mitigation, adequate power drip ride through, fieldbus connectivity and built-in control features to enhance the application.

Harmonic mitigation

Among some of the other considerations when selecting a drive is that not all harmonic mitigation is the same, not all drives are right for outdoor use and not all drives achieve the EMC regulations when connected to a motor.
ABB has addressed many of these challenges by incorporating hardware and software changes in its new ABB HVAC drive, ACH580 – a variable-speed drive dedicated to the HVAC sector.

ABB drives at discounted prices are available from 999 Inverters