Siemens SLI-5310 Instruções de Operação descarregar pdf (Página 21)

Diagram 2:

Shaft speed and resulting output frequency as a function of the number of

signal periods per revolution

Shaft speed [min

–1

]

Signal periods per revolution

Output frequency [kHz]

HEIDENHAIN absolute encoders for “digi-

tal” drives also supply additional sinusoidal

incremental signals with the same charac-

teristics as those described above. Abso-

lute encoders from HEIDENHAIN use the

EnDat interface (for Encoder Data) for the

serial data transmission of absolute posi-

tion values and other information for auto-

matic self-conﬁ guration, monitoring and

diagnosis. (See Absolute Position Values –

EnDat.) This makes it possible to use the

same subsequent electronics and cabling

technology for all HEIDENHAIN encoders.

Important encoder speciﬁ cations can be

read from the memory of the EnDat en-

coder for automatic self-conﬁ guration, and

motor-speciﬁ c parameters can be saved in

the OEM memory area of the encoder. The

usable size of the OEM memory on the ro-

tary encoders in the current catalogs is at

least 1.4 KB (f 704 EnDat words).

Most absolute encoders themselves

already subdivide the sinusoidal scanning

signals by a factor of 4 096 or greater. If the

transmission of absolute positions is fast

enough (for example, EnDat 2.1 with

2 MHz or EnDat 2.2 with 8 MHz clock

frequency), these systems can do without

incremental signal evaluation.

Beneﬁ ts of this data transmission technol-

ogy include greater noise immunity of the

transmission path and less expensive con-

nectors and cables. Rotary encoders with

EnDat 2.2 interface offer the additional fea-

ture of being able to evaluate an external

temperature sensor, located in the motor

coil, for example. The digitized temperature

values are transmitted as part of the

EnDat 2.2 protocol without an additional

line.

Bandwidth

The attainable gain for the position and

speed control loops, and therefore the

bandwidth of the drives for command

response and control reliability, are

sometimes limited by the rigidity of the

coupling between the motor shaft and

encoder shaft as well as by the natural

frequency of the coupling. HEIDENHAIN

therefore offers rotary and angular

encoders for high-rigidity shaft coupling.

The stator couplings mounted on the

encoders have a high natural frequency

up to 1800 Hz. For the modular and

inductive rotary encoders, the stator and

rotor are ﬁ rmly screwed to the motor

housing and to the shaft (see also

Mechanical design types and mounting).

Fault exclusion for mechanical coupling

HEIDENHAIN encoders designed for

functional safety can be mounted so that

the rotor or stator fastening does not

accidentally loosen.

Size

A higher permissible operating tempera-

ture permits a smaller motor size for a spe-

ciﬁ c rated torque. Since the temperature of

the motor also affects the temperature of

the encoder, HEIDENHAIN offers encoders

for permissible operating temperatures

up to 120 °C. These encoders make it pos-

sible to design machines with smaller mo-

tors.

Power loss and noise emission

The power loss of the motor, the

accompanying heat generation, and the

acoustic noise of motor operation are

inﬂ uenced by the position error of the

encoder within one signal period. For this

reason, encoders with a high signal quality

of better than ± 1 % of the signal period

are preferred. (See also Measuring

Accuracy.)

Bit error rate

With rotary encoders with purely serial

interface for integration in motors,

HEIDENHAIN recommends conducting a

type test for the bit error rate.

When using functionally safe encoders

without closed metal housings and/or

cable assemblies that do not comply with

the electrical connection directives (see

General electrical information) it is always

necessary to measure the bit error rate in a

type test under application conditions.

Data transfer in hybrid cables

For particularly limited spaces in machines

or drag chains, motors that contain encod-

ers with the EnDat22 interface can be con-

nected to the subsequent electronics

through hybrid cable technology. The HMC

6 hybrid cables save a good deal of space

because they contain all the lines for the

encoder, the motor, and the brake. Cable

lengths up to 100 m are permissible.

Properties and mounting

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