The Main Spindle Drive for Machine Tools

The SIEB & MEYER frequency converter FC71 is used for the vector-controlled drive of asynchronous and synchronous motors. Speeds up to 150,000 rpm can be reached. The vector control provides full torque at low speeds and allows back-magnetization of synchronous motors. Field-weakened motors can be accelerated up to their maximum speed. For machine tools, the frequency converters reach positioning accuracies of 0.007°. Beside precise orientation during tool change this also allows interpolated working with feed axes, for example in threading applications.

The High-End Drive for Maximum Machine Performances

In FC71, the function of FC72 is expanded by an active filter module at the motor output. This produces a sinusoidal output current as well as a sinusoidal output voltage, reducing losses caused by the converter to zero, and increasing the active power at the shaft. Another function of the active filter is excessive output voltage increase, which is reached via switched capacities. The combination of these two features results in an increase of the machine performance during high-speed cutting by up to 100% – an effect which could be proven repeatedly in real applications using competing products.