With integrated approaches to machine safety drifting onto the radar screen of more and more engineers over the past year, motion control suppliers are responding with drives that offer built-in safety functionality. One example of this growing safety focus comes from Lenze-AC Tech, which next month will add built-in safety circuits to two of its newest servo drives.
According to Brian Taylor, the company’s servo product manager, safety circuits will be added to the Model 940 and 941 PositionServo drives. By interrupting the drive output to the motor, these circuits will allow safe-standstill in accordance with EN 954-1 Category 3.
Taylor says Lenze drives have long offered optional safety circuits in Europe. “Now more North American engineers are moving in this direction,” Taylor says. And that move prompted Lenze-AC Tech to offer the circuit on this side of the Atlantic.
Those two recent drives, 940 and 941, are nearly identical. Both offer motion control options ranging from basic torque and velocity control up through programmable coordinated motion. Both can operate as just a basic drive or as a drive controller that stands alone.
The key difference between the two drives involves motor feedback. The Model 941, which is new to North America, features an integrated resolver rather than an encoder. “Resolvers are extremely rugged devices,” says Taylor. “And they’re still used extensively where encoders would have issues with heat or other environmental factors.”
To make this resolver-based model more flexible and capable of functioning in applications requiring tight position control, the company also built in an emulated encoder output. As Taylor explains, it provides fifteen levels of positioning resolution and does so in an encoder-like output that a variety of master controllers can recognize.
In the past, Lenze offered similar functionality in a module users could purchase for the Model 940. Now the resolver capability has been integrated into the new Model 941 at a cost savings of $60.