Smart connection for servomotors

With high levels of energy needed simply to provide the medium required for motion, pneumatic and hydraulic actuators are increasingly being replaced by electric drive systems.

Due to their simple construction and low costs, induction motors were previously the preferred choice for simple automation applications. However, efficiency levels stipulated  by energy saving initiatives mean that changes have to be made in the design of motors, and more copper and advanced magnetic metal are required. This increased volume of material, combined with the need for an improved cooling system and smaller air gaps, is driving costs upwards, so that the cost advantage compared to more efficient servomotors is being eroded.

For quick installation and startup of servomotors, as well ensuring that they operate reliably, connection technology is a key component. At present, most servomotors are connected with two interfaces: traditionally, the power interface connects the three phases plus ground wire for the drive and, depending on the design, has connections for the motor brake and the temperature sensor; the second interface connects the motor feedback system – a resolver as a robust, cost-efficient variant, or an encoder as a high-precision alternative – with the drive control.

Hollow shaft resolver

Since the final cable outlet direction is not known when the manufacturer delivers the motors, the rotatable, angled connector sockets with a rotation range of 330° allow it to be selected at any time, without tools and with no compromises in protection against environmental influences (IP 65, 66, and 67).

For reliable use of the motors in an environment that is frequently subject to vibrations, it is important that the connectors used are locked quickly and securely. The SpeedTec quick-release connector is installed three times faster than classic screw connections while granting backward compatibility.

Due to the increase in digitised motor feedback signals, the use of OCT (one cable technology) systems is growing, along with that of classic connection technology. With OCT systems, the two interfaces for power and signals are replaced by a single combined plug-in connector. In this system, in addition to the power wires, one or more shielded two-wire lines are connected to transmit the motor feedback signals and, optionally, to control the motor brake. The classic plug-in connection is the htec connector series, in which the signal lines are connected in an individual shielded data module with different numbers of contacts.

htec hybrid interface in M23 design

It is important that the cable shield is connected quickly, easily, and safely via the crown clamp element; here, the shielding braid is simply twisted into the element without being shortened. The simple plug-in connection is secured additionally in the insulator by the TE Connectivity Intercontec contact locking, which snaps into the side and needs no tools for assembly or disassembly.

Modern industrial data transfer systems used in motor feedback systems are very resistant to electromagnetic interference. This robustness is the basis for a new generation of connectors for OCT applications. These connectors, which use a symmetrical, balanced contact arrangement, have no separate shield element for the data lines; this has no effect whatsoever on data transfer performance.

The latest product in this new generation is the world's first OCT motor plug-in connector with the M12 form factor. Its determining technical features are:

- Pin configuration in 3x power + PE + 4 or 6 signals
- Maximum rated voltage, 8-pole variant: 630 V AC/DC
- Maximum rated current, power contacts: 8A
- SpeedTec quick lock
- Rotatable angled receptacle.

With OCT solutions, using just one interface reduces the costs for electrical engineering on the servomotors as well as the expenditure for cabling in the application. This is because less material is used and installation times are shorter.

In addition to the M12 variants, this connector family is constantly being expanded to include larger designs such as M17 and M23 and, consequently, higher power classes. Because of the changed form factor and the adjusted electrical parameters on the power side, these have the same properties as the M12 connectors described here.