Motor wiring explained
Original article date: September 1999
What is the best way to connect up that motor? Tommy Miller dips into the new wiring manual from Klockner-Moeller
Anybody who works with low-voltage switchgear is likely to find Klockner-Moeller’s new book extremely useful, whether they’re a trainee or an experienced electrical engineer. And because it’s free, there’s no reason not to have a copy!
The book, simply called the Wiring Manual, covers most of the important circuits used in automation and power distribution applications, but it is particularly good for anybody configuring and operating electric motors. Indeed, at the heart of the book is a substantial section called All About Motors.
This key chapter runs to 122 pages (yes, really!) and discusses everything from motor protection and the incoming supply, to various methods of starting motors and controlling motor speeds. Many standard and sample circuits are included, together with tabulated and graphical data where this is appropriate. As well as circuits for direct-on-line starting and star-delta circuits, there are also examples of multi-speed and other miscellaneous circuits
The text is written in straightforward, no-nonsense language, and often comes in a question and answer format. For example: ‘What causes destruction of the overload relay? Destruction will take place only in the event of a short circuit on the load side of the relay when the back-up fuse is rated too high. In most cases this will also endanger the contactor and motor. Therefore, always adhere to the maximum fuse rating specified on every relay.’
Besides the main section on motors, the Wiring Manual also deals with many other related matters. For instance, comprehensive information is included on standards and specifications, there is a comparison of European and North American circuit symbols, units of measurement are tabulated, formulae are reproduced and there is even a table of cable entry and grommet sizes.
Another valuable section within the book considers how motors and control gear should be wired when there is a guard interlock with a mechanical securing action. This will be especially useful for those engineers who are responsible for original equipment or refurbished equipment where CE-marking is an issue. Lists of approvals bodies for different countries, together with marking requirements, will help engineers to target the products for any market world-wide.
Lastly there is, of course, a list of Klockner-Moeller’s sales offices around the world, so you can always be sure of getting hold of the hardware and assistance that you need. Meanwhile, the book itself is highly recommended.
- Klockner-Moeller
September 1999