Siemens SLI-5310 Instruções de Operação descarregar pdf (Página 28)

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Electronic commutation with position encoders

Commutation in permanent-magnet

three-phase motors

Before start-up, permanent-magnet three-

phase motors must have an absolute

position value available for electrical

commutation. HEIDENHAIN rotary

encoders are available with different types

of rotor position recognition:

• Absolute rotary encoders 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.

• Incremental rotary encoders with a

second track—the Z1 track—provide

one sine and one cosine signal (C and D)

for each motor shaft revolution in

addition 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 control from the incremental

track (see also Interfaces—Commutation

signals).

• Incremental rotary encoders with

block commutation tracks also output

three commutation signals U, V and W.

which are used to drive the power

electronics directly. These encoders are

available 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 incremental square-wave

signals serve for position and speed

control. (See also Interfaces—

Commutation signals.)

Commutation of synchronous linear

motors

Like absolute rotary and angular encoders,

absolute linear encoders of the LIC and LC

series provide the exact position of the

moving motor part immediately after

switch-on. This makes it possible to start

with maximum holding load on vertical

axes even at a standstill.

Circular scale with

serial code track and

incremental track

Circular scale with Z1

track

Circular scale with

block commutation

tracks

Keep in mind the switch-on behavior of

the encoders (see Interfaces catalog,

ID 1078628-xx).

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