•• • Circular scale with serial code track and incremental track Circular scale with Z1-track Circular scale with block commutation tracks

Electronic Commutation with Position Encoders

Interfaces—Commutation signals. ) Interfaces—Commutation signals ). Commutation of synchronous linear motors Like absolute rotary and angular encoders, absolute linear encoders of the LC series provide the exact position of the moving motor part immediately after switch-on. This makes it possible to start with maxi- mum holding load on vertical axes even at a standstill. Incremental rotary encoders with block commutation tracks Commutation in permanent-magnet three phase motors Before start-up, permanent-magnet three- phase motors must have an absolute posi- tion value available for electrical commuta- tion. HEIDENHAIN rotary encoders are available with different types of rotor posi-tion recognition: also output three commutation signals I, II, and III, which are used to drive the power elec- tronics directly. These encoders are avail-able with various commutation tracks. Typical versions provide 3 signal periods (120° mech.) or 4 signal periods (90° mech.) per commutation and revolution. Independently of these signals, the in- cremental square-wave signals serve for position and speed control. (See also Absolute rotary encoders Incremental rotary encoders with in singleturn and multiturn versions provide the abso- lute position information immediately af- ter switch-on. This makes it immediately possible to derive the exact position of the rotor and use it for electronic com-mutation. a second track—the Z1 track —provide one sine and one cosine signal (C and D) for each motor shaft revolution in addi- tion to the incremental signals. For sine commutation, rotary encoders with a Z1 track need only a subdivision unit and a signal multiplexer to provide both the absolute rotor position from the Z1 track with an accuracy of ± 5° and the position information for speed and position con- trol from the incremental track (see also Keep in mind the switch-on behavior of the encoders (see General Electrical Information ).

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