Invertek’s Technical Manager, Kes Beech, explains why STO is critical when variable speed drives are used to control motors in industrial machinery.

“STO is the abbreviation for Safe Torque Off. Where AC drives are used to control the speed of motors in machinery applications, it is critical to ensure the safety of operators and personnel through correct design, and to evaluate potential risks.

Features such as Optidrive P2’s TUV approved STO function are intended to simplify the integration of the drive into the machine in a safe manner.

When the STO function is activated, it ensures that no torque is produced at the motor shaft. This is achieved in the drive hardware, using a specially designed circuit to ensure that the operation is failsafe.

The benefit to machine manufacturers and end users here is that the drive can now be used as part of the safety system of a machine, simplifying the overall design and removing the need for additional safety components. With an approved STO, the drive can be used as part of the safety system, providing it is installed as per the recommendations and meets the safety standards required by the machine.”

Kes continues, “As a global market leader, Invertek invests a significant amount of resources into product development. We are constantly improving our products and services to benefit our customers. Optidrive P2’s STO feature, which carries TUV approval, eliminates the need for additional components in some applications, making machine design simpler and reducing costs.”

Invertek’s STO function is independently certified by TUV to meet the following standards:
-              EN61800-5-2:2007 Type 2
-              EN61508 (Part 1 to 7) SIL 2
-              ISO13849-1:2006 Pl”d”
-              EN60204-1 Uncontrolled Stop Category 0
-              EN62061 SIL CL2