To ensure a reliable electrical connection over the entire service life of servomotors, the connectors used must have a robust mechanical design and be able to withstand vibrations and shocks. They must not be affected by temperatures of +80 °C and above, which frequently occur during operation, nor must they have an unacceptable influence on their environment through the emission of electromagnetic fields. These fields often occur with servomotors in particular, as they are driven by a modulated square-wave voltage due to their operating principle. Electromagnetic compatibility legislation stipulates that interference emissions must be kept as low as possible. Another requirement that plug connectors for machine tool motors in particular must meet is a high level of protection against the ingress of liquids and foreign bodies.

Until around 25 years ago, motor connectors were strongly geared towards military standards, particularly in terms of design, shield connection and cable sealing. Although they could be used in industrial automation, they were not ideally suited to this scenario: they were bulky, the contacts could usually not be crimped but had to be soldered on, and the shielding connection was complex and of low quality. As there was also only one cable outlet direction on the motor side in most cases - the principle was often straight installation of the connector and angled cable plug - comparatively high installation spaces had to be provided.

Industrial connection technology

New generation of hybrid connectors for power, signal and data transmission for OCT applications (one cable technology).

© TE Connectivity

In the mid-1990s, TE Intercontec launched the first circular connector for motor connection technology, which was based on die-cast zinc technology and was specially developed for industrial automation. This technology also formed the basis for further developments in this field up to the present day.

It began with a 330° rotatable angle housing for motor attachment. This was followed by a locking system that ensures an installation time that is three times faster than standard screw locking. Other milestones included the first hybrid circular connector, which can transmit signals, data and power, and the smallest single-cable solution for motor connectivity based on M12 dimensions. The crown clamp enabled time-saving shield contacting across all designs, as the shield no longer needs to be cut, but is rolled up using a special mechanism, similar to a garden hose.

The technical challenges that had to be overcome in order to realize these developments are illustrated by the example of hybrid circular connectors. In order to transmit signals and data as well as power, not only is a high packing density of the contacts required, but the integrity of the data and signals must also be ensured in an environment with electromagnetic fields. Special attention therefore had to be paid to ensuring that the clearance and creepage distances specified for use in industrial automation are guaranteed, even though contamination is always to be expected in this environment, which can also be temporarily conductive. TE's hybrid circular connectors typically have four power contacts for currents of up to 30 A as well as a maximum of six contacts for signals and up to three separately shielded contact pairs for data, all of which are integrated into an M23 housing.

Compliance with electrotechnical standards

This is achieved by a precise symmetrical design of the mating face and by the fact that the data is normally transmitted via shielded 2-wire lines and thus common mode interference is strongly suppressed. A separate shielding element is used to ensure the necessary shielding of these sensitive cables. To ensure that the hybrid connectors can be easily assembled without special tools despite the high packing density, they have multi-part, hinged contact carriers into which the contacts are clipped from the side.

The NFC chip in the connector can be read using a standard smartphone.

© TE Connectivity

With the circular connectors, motor manufacturers only have to implement one interface instead of two, as was previously the case when using hybrid circular connectors. System operators can reduce the cabling effort and connect the motors more quickly. On the other hand, flexibility is increased. This is because the 330° rotatable angle housing for motor attachment ensures that the cable outlet direction can be determined on site, which is helpful in special machine and plant construction, for example. Otherwise, motor manufacturers have to provide versions with different cable outlet directions to meet different installation requirements. In addition, the rotatable angled housings make installation easier in that the connectors can be plugged onto the motor where they can be easily reached by hand and then rotated away from the installation space so that the cables do not interfere. The circular motor connectors are easy to assemble and their robust design makes them resistant to vibrations and shocks as well as harsh environmental conditions and electromagnetic fields.

'Intelligent' motor connection

TE is working on further solutions to further improve the handling and functionality of circular motor connectors. One example is magnet wire connection technology, which is already used in the automotive sector and for consumer goods. In many motors (e.g. for fans or washing machines), it is now common practice to connect the enameled copper wire for the motor windings using 'MagnetWire' technology based on insulation displacement technology rather than stripping it using mechanical, thermal or chemical processes before further processing. As this process is increasingly being used in industrial motors, TE's new solution is intended to enable a simpler connection between the outer motor connector and the inner motor winding.

Another market-ready development provides 'intelligent' motor connection technology. The circular connectors will be equipped with an RFID chip to ensure that they can be uniquely identified. In a second step, this should also be possible for complete cable assemblies. This will allow these products to be tracked precisely or additional information such as quality documents, parts lists or order data to be viewed via the cloud. This will also bring motor connectivity to the web.

Author:
Claus Kleedörfer is the Global Product Manager responsible for the Intercontec product portfolio at TE Connectivity Industrial in Niederwinkling.