HARTING North America was recently asked to solve some of the problems associated with power distribution and motion control on a vehicle manufacturer’s long conveyor and engine block production line. The line’s system integrator needed to reduce installation costs to be competitive with other potential suppliers, and the end customer was looking for higher reliability and ease of maintenance.
The two key inputs to the drive motors for the conveyor and transfer mechanisms are, of course, electrical power and control signals. The power is 480VAC, and the control signals are 24VDC. The fieldbus being used for drive motor control is the ASIBUS, in addition to PROFIBUS and PROFINET for other control applications.
Since the conveyor line is assembled in sections, a key design element is how power and control lines are routed to the drive motors. This wiring and interconnection design also has a large impact on installed cost and serviceability. In earlier conveyor line wiring, a common practice was to run separate power and control lines to drive motors. Sometimes, the lines ran directly from control panels to the drive motors; in other cases these lines went through separate power and control line connectors on the conveyor line. Both approaches resulted in the use of a lot of copper and high installation costs.
Rather than continue with these practices, the system integrator asked HARTING to suggest ways to interconnect all the drive motors on the engine line. The goal was to reduce the number of long wiring runs back to control panels, and further reduce installation cost. HARTING proposed its Han- Power® T connector. This product facilitates interconnection of the drive motors with a composite trunk cable containing both power and control signal wiring, and also provides an easy way to make individual power and control drops to each motor.
A key element in this connection design is the ease of installing and servicing these cable drops. Instead of two different connectors for power and control, a single Han-Power T connector has a contact arrangement custom tailored for both types of wiring. Power and control lines traverse the “top” part of the T as feed-throughs, while drops to individual drive motors exit the connector via the “down leg” of the T (see Fig. 1). By pre-engineering cables and motor drops in this fashion, on-site installation time is reduced, along with the high costs and wiring errors that are common in hardwired solutions.
The control lines use a smaller wire size than the power lines to conserve on copper usage and hold down costs. This means different pin size inserts for the two different lines, which in this case have 10AWG wire for the power circuits, and 16AWG for the signal channels. Mechanically, internal conductors must provide both the straight feed-through and right angle electrical paths, and the connector as a whole must pass UL testing. While various vendors were willing to create a custom designed connector of this sort, getting it done and conforming to UL requirements in an acceptable time span was another matter.
The Han-Power T is customizable, built from off-the-shelf components, and assembled in HARTING’s Elgin, IL Value Added Business (VAB) facility. HARTING’s VAB is a UL approved cable assembly facility, which was one of the end customer’s requirements for a cable/connector supplier for the conveyor line installation.
The Power T system is rated for up to 600VAC power service, and up to 250V signal service. Power and signal inserts for the connector are available in different configurations for different wire sizes and current carrying capacity. For added safety, there is a locking clip on the Han-Power T connectors, which prevents inadvertent disconnection while the system is powered up. The locking clip must be removed manually before disconnecting the power and signal lines at the T connector, which is normally done only after electrical power is turned off.
In keeping with the need for a high level of safety, an IP67-rated housing was installed on each drive motor. This housing has an M12 connector with HARTING’s Han Q8/0 insert, which includes both power and control wiring contacts. If anyone should pull one of these connectors apart while the system is under power, this trips a safety input and powers down the system. Short contact pins are used in the connector for this control feature, which means the safety trip is executed before longer pins disconnect power to the drive motor, thereby preventing an arc flash and injury to personnel and equipment.
More than 600 Han-Power T connectors are being used on the custom cable assemblies being made in HARTING’s Elgin plant for the conveyor line. By adopting this connector, the system integrator has gained the advantage of design flexibility, with the further benefit of off-the-shelf hardware and the economical pricing that goes with it. The end customer benefits from wiring and connector designs that are highly reliable and easily serviced.
The end result is a conveyor design that’s entirely modular, making it the most economical solution. Instead of assembling major sections in the integrator’s shop, modular units are shipped to the engine plant that’s under construction. Since cables and connectors are clearly labeled, electrical assembly can take place even without construction drawings. The electricians involved with the installation have commented that the modular design also requires minimal use of tools. Occasionally, a screwdriver is required for some mechanical assembly, but otherwise the HARTING Han-Power T connectors make this a snap-together design.