AIR QUALITY
s imply be because the VSD is at the end of its life. A well-defined life cycle management plan identifies all potential risks of failure and m inimises them by ensuring that the VSD is m aintained to the highest standards.
V SDs are, generally, highly reliable devices. A d rive could have a mean time between failures of 200,000 hours, a very respectable 23 years. But it can only achieve these numbers if everything is right. There are three main reasons why a VSD may fail.
T he first is simply because they are the wrong drive. They are badly specified, wrongly sized or b oth and are therefore working too hard in the application. A second reason is that they have been badly installed. This can incorporate issues such as an incorrectly dimensioned cabinet, inadequate airflow, an ambient temperature that is too high or too low, or loose connections. The t hird main reason is poor or even non-existent maintenance.
Examples include fans not being replaced
according to the manufacturer’s instructions and inadequate inspection or cleaning. In particular, heat sinks need to be kept dust free so air can fl ow freely and cool the drive properly. Note that for a 10 degree rise in operating
t emperature, capacitor life is halved. Conversely, b y keeping temperature 10 degrees lower, by m aintaining the fan properly, capacitor life i s doubled. Any aging components should be replaced regularly. To decrease the probability of electronic components failing, drives may have to operate in a well air-conditioned electric r oom, over pressured and where temperature, r elative humidity and air pollution are regularly m onitored. Drives need to be kept dry so moisture d oes not corrode circuit boards. Ensuring connections are kept tight to prevent damage from arcing is another essential. It has been estimated that 80% of drive failures occur due to a poor maintenance regime.
T he main benefit of life cycle management is t hat it enhances the condition and reliability of VSDs and extends their operating life. To achieve this, it makes the correct resources and parts available to implement upgrades, while providing lower cost of ownership and minimal disruption. T aking a whole life approach to drive servicing a nd replacement is the only sure way to get cost-effective, extended use from valuable plant assets and in turn ensure that quality, safety, compliance, production time and revenue is maximised.
New motor technologies ew motor technologies
A common feature of older HVAC systems is the over-sizing of motors. Replacing these with modern synchronous reluctance motors (SynRMs) could bring many additional advantages to a HVAC installation.
The IE4 SynRM and drive package gives super premium efficiency that allows specific fan powers to be achieved. SynRMs match the footprint of induction motors, therefore offering an easy replacement.
A high output varian t which is two frame sizes smaller allows for easy mounting within a duct. The motors are lighter, run cooler and quieter and are more efficient than induction motors.
SynRMs do not create excessive harmonics which can pollute the electricity supply, and can catch spinning loads. They do not generate dangerous back EMF voltages so that local isolation still protects the operator. Whether you want to enhan ce energy
efficiency, save on maintenance, reduce trips and cut inrush currents or get a better control of your HVAC to ensure it is fit for how you currently use it, retrofitting a modern VSD c ould be the answer.
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