Wednesday, 3 December 2014

Andy Preston, UK Drives Product Manager, ABB writes: Modern variable-speed drives are smart, with lots of impressive technology. But do they help you work in a smarter way – better process control, more intuitive operation, better safety for your staff, faster resolution of problems? What makes a truly ‘smart drive’.

What does ‘working smartly’ mean to you? One definition could be that you don’t have to think too much about the way you or your process works – all the hard work has been done before hand. Everything happens as it should, in the right way and as you’d expect it to.

Take the keypads of variable-speed drives (VSDs). This is where you ‘interface’ with the drive – where it tells you what is happening and where you tell it what to do. This is much easier if it talks your language – literally. Plain English is much more preferable to codes and symbols that you have to interpret or memorise.

The best keypads will help you work smarter by presenting information clearly, perhaps with graphs and charts to make complex information instantly understandable. Combine this with large, easy to use keys, a screen that can be read in any light conditions and a menu that is child’s play and you’re onto a winner.

Taking out the guesswork should also be the basis of determining faults or other process events. Let’s get one thing straight – a drive tripping is not a problem, but a symptom of the problem. It is supposed to do that to protect the motor and process machinery.

But once these events have occurred, how easy is it to discover their source and decide how best to resolve them? Smart diagnosis starts with the keypad. The best keypad screen will display flashing icons and pictures to attract attention and show the reason for the event. With a clear display, it is easier to see exactly which drive has tripped, allowing it to be quickly tracked down.

Yet, the best diagnostic methods don’t end there. A lot of diagnostic work should go on behind the scenes, making sure those process problems never arise in the first place. Trip histories can allow you to spot patterns of events. If they are also time stamped, the frequency of an event can be easily tracked, allowing preventive maintenance to be performed before a major issue occurs.

Some of the latest drives also have a system that can package all the fault and trip information and send it straight to the vendor for analysis. Again, it takes the leg work out of diagnosing faults, saving time and meaning you get to the solution more quickly and efficiently.

When it comes to safety functions, you also want them to be ‘smart’ – ready built-in, dependable and always ready to step in to save the day.

Separate safety systems all add to the time and expense, as well as increasing complexity. Surely there is a better way? When it comes to drives, they should take the safety functions on board, removing the need for external components. STO or Safe Torque Off is a must have and should be part and parcel of the drive.

Others, such as SS1 (Safe Stop 1), which ramps the controlled motor down to zero speed; and SBC (Safe Brake Control), used for proper safe management of a crane brake, are less often needed and could be provide in an external module which you can take or leave. What you need is provided – what you may not need is optional.

Of course, the whole point of a VSD is to control motors – so the smart way is to have the VSD control as many different types of motors as possible, be they squirrel cage, permanent magnet or SynRM. That way, you can cut the number of ordering procedures, the number of vendors and the spares stock.

The smartest drives come with the things you need to help you work smart. They make your life easier, your machinery safer and your processes more productive. Smart design means you don’t have to worry about your VSDs but can get on with what you do best.

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