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Innovations Simplify the Installation of Motor Starters
![[picture of xStart units]](images/xstart_units.jpg)
Moeller
has introduced the xStart range of motor starters, which
raises the benchmark for its competitors. Thanks to a pair of
design innovations – one of which is deceptively simple –
electrical engineers and panel builders gain valuable savings in
both time and panel space, as described by Product Manager, Steve
Rickard.
With wiring times and effective use of cabinet real-estate climbing ever higher on the agenda of many design and installation engineers, Moeller's two new developments will introduce a breath of fresh air into what is a mature product market.
The first and most apparent development is a two-part 'tool-less' plug connector module that combines both electrical and mechanical connections between a PKZM0 motor-protective circuit-breaker and a DIL M contactor. On DOL starters, components are simply 'clicked' together instead of the more traditional fastening of cables with six screws. When joined, the two units form a complete MSC motor starter that offers a capacity up to 12A (5.5kW,AC-3, 400V). Reversing starters using the 'tool-less' plug technology are also available up to 5.5kW, AC-3, 400V.
This clever connection technology delivers several benefits. The mechanical element of the connector ensures a safe and stable connection of the motor-protective circuit -breaker and contactor, which can be mounted on a single top-hat rail. The MSC-D DOL starter or MSC-R reversing starter can even is assembled beforehand, outside of the control cabinet. The electrical connector module provides the main connection of the contacts between the two units, reducing fitting costs and eliminating wiring faults.
The rigid connector modules used, instead of conventional flexible cables, considerably reduce the height of the assembly. They also remove the need for cutting cables to length, cable stripping, labelling and termination so reducing installation times. On reversing starters, the time consuming wiring of 23 terminal points, such as with paralleling or reversing links is no longer necessary.
Another advantage lies in increased safety during maintenance work where removal of the electrical connector module provides a visible isolating gap. Where panel space is an issue, by running across the front of the units, the interconnecting devices do not add any additional width or height to panel assemblies – unlike other connection methods. The contactor and protective switch come in a standard 45mm width, the ideal design width for rail mounting and mounting on busbar adapters. AC and DC contactors are the same size and geometrical design, making planning, engineering and fitting easier.
Reversing and star-delta combinations also benefit form the plug connector design. Star-delta combinations consist of three contactors (mains, delta and star) as well as a timing relay. Four plug-in connectors replace the 21 terminal points of conventional wiring.
The other development – which is far less obvious, but just as ingenious – is a simple safety mechanism that prevents the two contactors in a reversing starter arrangement switching simultaneously. EN 60204-1 stipulates that reversing starter combinations must be interlocked in such a way that a short-circuit cannot happen when switching in normal operation. Using a small ball in a recess between the two contactor bodies, a mechanical interlock is achieved without any additional mounting space.
As one contactor moves into its 'on' position it displaces the ball towards, and slightly into, the other contactor creating a physical barrier preventing it from switching. It really is that simple, and Moeller's solution, for which a patent has been applied, is far less complicated than others currently available on the market.
Moeller's xStart range also includes Z overload relays and DILA contactor relays. All elements within the range have been designed to work in harmony with each other, giving designers and panel builders a complete and comprehensive range of motor control options. In addition to the modular system, Moeller offers pre-assembled and ready to install complete assemblies, which further reduce installation time and considerably simplify the engineering process.
