Spindle Motor Control with KEB Drives

With over 500,000 installed spindle drives, KEB has earned a reputation as the worldwide spindle drive leader. This post describes why our CNC, woodworking, and robotics customers prefer KEB.

Spindle Motor Control

Adjusting a drive parameter allows KEB drives to run induction and permanent magnet spindle motors. KEB’s robust motor control algorithms mean it can run various motor designs from all major spindle motor manufacturers. Basic applications can utilize V/Hz control. The advantage of V/Hz is its simplicity and ease of commissioning.

Closed-loop applications can be solved using KEB’s dual-channel encoder interface. Many feedback formats are supported, including Incremental TTL/HTL, Resolver, EnDAT 2.1/2.2, Hiperface, etc. Tool change and orientation functions can be programmed in the drive. This possibly allows the PLC or controller to be removed from the system.

Closed-loop drives offer the additional feature of torque limits. Different sets can be programmed, allowing several different torque limits to match the motor operating characteristic, ensuring the motor does not become overloaded.

KEB’s unique SCL and ASCL (Sensorless Closed Loop, Asynchronous Sensorless Closed Loop) control technology can provide closed-loop performance without needing encoder feedback.

Spindle Performance

Newer drive platforms like the S6 feature a fast current control loop of 62.5µs. This provides excellent spindle motor performance and a better final product.

KEB drives are offered in switching frequencies up to 16kHZ with output frequencies up to 1667 Hz for high-speed applications. This allows motor speeds over 100,000 rpm while minimizing motor noise and heating.

KEB drives are offered in sizes from fractional horsepower up to 1000 Hp. For 3-phase installations, 230VAC and 460VAC voltage classes are available. Additionally, a single-phase 230VAC variant is offered.

Ethernet On Board

Although KEB drives support various communication protocols like Ethernet/IP, Powerlink, and Profinet – we have standardized on EtherCAT. EtherCAT communication offers excellent real-time performance, is an open technology with many vendors and members, and offers tremendous value for its performance.

EtherCAT is well suited to demanding, high-performance applications. For example, the S6 platform supports a 500 µs scan time for up to 8 parameters (up to 32 bytes). The EtherCAT process data can send a home or orient command to the drive. This can be used for a basic home start or a tool change. The S6 drive will use the zero pulse from the encoder to position the spindle for a tool change.

Positioning can also be done over EtherCAT. The desired position (position counts either relative or absolute) can be written to the drive directly over EtherCAT. Alternatively, predefined positions can be stored in the drive, and the PLC can select which position the system should move to and send that signal over EtherCAT.

Functional Safety

Along with the benefits of EtherCAT mentioned above, KEB drives offer functional safety options. Safe-Torque-Off (STO) is offered as standard. More advanced Safe Motion functionality according to ISO 13849 is available, including SS1, SS2, SOS, SLS, SLP, SLI, SDI, and SSM.  Additionally, SM3 is an FSoE Servo Drive that allows all safety functionality to be carried over the protocol.

One advantage of moving Safe Motion into the drive is that the drive’s high power does not need to be removed in certain situations. An example would be when an operator opens the machine tool door to clear debris. Traditionally, all power would be cut from the drive so the motor does not unintentionally start. But this requires the operator to wait so the drive bus capacitors can discharge and recharge again.

KEB’s SIL3 Safe Motion functions can achieve this same functionality through our Safe control card and 24V inputs. High power remains connected, which ultimately allows for machine operation.

KEB Spindle Drives – 500,000 and Counting

Contact a KEB America engineer for your next spindle drive application.