Siemens EK 726 Series Manual de Serviço descarregar pdf (Página 42)

ENGINEERING INFORMATION AND INSTRUCTIONS

MICROMASTER

MICROMASTER Vector

MIDIMASTER Vector

SIEMENS DA 64 – 2002/2003

Version D 3/18

3.10 Selection aid for motors

A detailed description of the motors and selection tables is

provided in the following Catalogs:

M 11: Three-phase low-voltage squirrel-cage

induction motors

DA 47: Reluctance motors: Synchronous motors for

variable-speed drives

DA 48: SIEMOSYN motors: Synchronous motors

for variable-speed drives

The technical guidelines, specified here, refer to Siemens

1LA5, 1LA6 and 1LA7 low-voltage motors as well as the

Siemens 1LA5 force-ventilated motors. If third-party motors

are used, then their specific technical data must be carefully

observed.

All types of load characteristics are conceivable; only the most

important are discussed here:

- constant-torque drives

If M = const. ("Constant torque", CT)

- blower and pump drives

with M ~ n² ("Variable torque", VT).

Motor torque utilization:

Which motor is best suited for a specific application depends

on its permissible torque characteristic over the speed range.

Typical characteristics for the continuous permissible torque

of a non-ventilated motor with a rated frequency of 50 Hz are

shown in

Fig. 1. The torque which can be used at low speeds

is significantly lower than that at 50 Hz due to the lower

cooling effect. The torque reduction factor is not the same for

all motors. The assignment tables below specify the torque

reduction as a function of the speed in the frequency range

f = 0 Hz to 50 Hz when utilized according to temperature rise

Class F.

For frequencies, which lie above the rated frequency

, the

voltage remains the same if the maximum drive inverter

output voltage has been reached. The motor is operated with

field weakening in this range. The torque, which can be

thermally used, decreases with approx.

/f. The stall torque

decreases as a function of (

/f)

which means that the safety

margin to the stall torque decreases and the load capability of

the drive decreases.

For MICROMASTER and MIDIMASTER drives with a field-

weakening range of

f = 50 Hz to 100 Hz, the load capability

for 1LA5, 1LA6 and 1LA7 motors drops to approx. 10% at 100

Hz.

The assignment tables indicate that Siemens

1LA5/1LA6/1LA7 low-voltage motors can be generally

operated with 100% rated torque if they are utilized according

to temperature rise Class F in a 1:2 control range. If they are

operated in accordance with temperature rise Class B, then,

for 1LA5/1LA6/1LA7 motors, the permissible torque must be

reduced by approx. 10%.

Force-ventilated motors:

In addition to non-ventilated 1LA5, 1LA6 and 1LA7 motors,

force-ventilated 1LA5/1LA7 motors can be used. According to

Fig. 1, the permissible S1 torque at the rated frequency can

be used down to standstill.

It makes sense to use force-ventilated motors if a high torque

utilization is required, even at the lowest speeds.

Standard motors with pole numbers > 4 should be operated

with speeds > approx. 2200 RPM (e.g. in the field-weakening

range). For non-ventilated motors, the fan noise can be

reduced in this way.

Field-weakening

operation

Constant flux

range

For forced ventilation

Utilized acc. to temp. rise

Class F

Utilized acc. to temp. rise

Class B

10 20 30 40

60 70 80

100

M/M

f [Hz]

Fig. 1: Typical characteristics of the permissible

torque for force-ventilated motors

(e.g. 1LA5/1LA6/1LA7) with a rated frequency

of 50 Hz. (precise data for 1LA5, 1LA6 and

1LA7 motors should be taken from the

assignment tables further below).

Maximum speeds:

The maximum mechanical speeds of 1LA5, 1LA6 and 1LA7

motors are specified in Catalog M11.

1 2 ... 37 38 39 40 41 42 43 44 45 46 47 ... 119 120

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