A LARGE number of modern applications call for some form of motor speed and/or position monitoring – be it just so a system knows the motor is rotating and in which direction, or to know the actual position of the machine.
The SEW-Eurodrive DR series of high efficient AC motors and geared motors has solutions for most types of applications from its range of encoder types. Traditional encoders are high resolution types with Sine/Cosine, HTL or TTL signal that are added to the non-drive end of the motor. These tend to be expensive and require a high level of control, either through high speed counter cards for PLCs or specifically designed motor speed controllers.
There are many applications that do not require this level of sophistication and accuracy, and to cater for this SEW-Eurodrive has developed a new internal encoder series that can be utilized with more simple systems.
For many applications, it is only necessary to detect that the motor is actually rotating and/or in which direction, at what speed – or to have the motor carry out a basic positioning task.
With this possible solution in mind, SEW-Eurodrive has developed a unique and cost effective pulse encoder. The SEW-Eurodrive internal motor encoder EI7 series has modules for 1, 2, 6 and 24 pulses per motor revolution, with push/pull 24VDC HTL signal for motor sizes from 0.37kW to 7.5kW.
Embedded in the special motor fan is an alternatively magnetized ring with 24 segments. Mounted to the back on the motor non-drive end ‘endshield’is a sensor module which has 2 Hall effect transducers which produce channels A and B with a 90-degree phase shift. The inverse channels A/ and B/ are also generated.
Encoder connection is either via terminal strip inside the motor terminal box or an externally mounted M12 connector on the side of the terminal box. The EI7 series encoder can be retrofitted to existing DR AC motors.
Positioning applications can be carried out in conjunction with a PLC using a step pyramid profile or by incorporating a SEW-Eurodrive Movitrac B series open loop controller. Positioning accuracy is around 90-degrees of motor rotation, which is further reduced by the inclusion of a suitably selected gear unit.
SEW-Eurodrive Movitrac B also have application modules for rotary table positioning and positioning by Bus for use with the internal encoder, and in most cases a motor brake is required to hold position targets.

Contact: peter@sew-eurodrive.co.nz