Weir Warman 650 M200-MCR-G, Manual, Page: 118 / 287

TOROMOCHO PROJECT - WEG MOTORS
TAG´s :
210-PP-001-M 210-PP-003-M 210-PP-101-M
210-PP-002-M 210-PP-004-M
- Bearings: Ball
- Standards: NEMA MG-1
- Voltage: Single phase: 110/220V
Three phase: 220/380V
- Frequency: 60Hz and 50Hz
For more information referring to motor features, please contact WEG.
3.2 - ELECTRICAL ASPECTS
3.2.1- POWER SUPPLY SYSTEM
Proper electric power supply is very important. The choice of motor feed conductors, whether branch or distribution
circuits, should be based on the rated current of the motors as per IEC 34 Standard. NOTE: In the case of variable
speed motors, the highest value among the rated currents should be considered. When motor operation is intermittent
the conductors should have a current carrying capacity equal or greater, to the product of the motor rated current times
the running cycle factor shown in Table 4.
IMPORTANT: For a correct choice of motor feed conductors, we recommend to check the standards requirements for
industrial installations.
3.2.2 - STARTING OF ELECTRIC MOTORS
Induction motors can be started by the following methods:
DIRECT STARTING
Whenever possible a three phase motor with a squirrel cage should be started directly at full voltage supply by means of
contactors. It has to be taken into account that for a certain motor, torque and current curves are fixed, independently of
the load, for constant voltage.
In cases where motor starting current is high, this can cause interference to the following:
a) Significant voltage drop in the power supply feeding system. As a consequence, other equipment connected to the
same system can suffer interference.
b) The protection system (cables and contactors) must be overdesigned leading to a high cost.
c) Power supply utilities will limit the supply voltage drop.
In cases where DOL starting is not feasible due to above given reasons, then indirect system can be used in order to
reduce the starting current such as:
- Star-delta starting
- Starting with compensating switch (auto-transformer starting)
- Series-parallel starting
- Electronic starting (soft-start)
STAR-DELTA STARTING
It is fundamental for star-delta starting that three phase motor have the required number of leads to allow connection on
both voltages, that is, 220/380V, 380/660V or 440/760V.
These motors should have at least 6 connecting leads. The starting has to be made at no load. The star-delta starting
can be used when the motor torque curve is sufficiently high to guarantee acceleration of the load at reduced voltage. At
star connection, current is reduced to 25% to 30% of the starting current in comparison to delta connection.
Torque curve is also reduced proportionally. For this reason, every time a star-delta starting is required, a high torque
curve motor must be used.
WEG motors have high starting and breakdown torque. Hence, they are suitable in most cases for star-delta starting.
The load resistant torque can not exceed the motor starting torque, neither the current when switching to delta
connection can not be of an unacceptable value.
There are cases where this starting method can not be used. For example, when the resistant torque is too high. If the
starting is made at star, motor will accelerate the load up to approximately 85% of the rated speed. In this point, the
switch must be connected at delta. In this case, the current which is about the rated current jumps, suddenly, which is in
fact not advantageous, as the purpose is to reduce the starting current. Table 5 shows the most common multiple rated
voltages for three phase motors and their use to the usual power supply voltages. The DOL or compensating switch
starting is applicable to all cases of table 5.
STARTING WITH COMPENSATING SWITCH (AUTO-TRANSFORMER)
This starting method can be used to start motors hooked to the load. It reduces the starting current avoiding in this way
overload giving the motor enough torque for the starting and acceleration. The voltage in the compensating switch is
reduced through an autotransformer which normally has TAPS of 50, 65 and 80% of the rated voltage.
SERIES - PARALLEL STARTING
For series-parallel starting, motor must allow reconnection for two voltages:
The lowest to be equal to the power supply voltage and the other twice higher.
This starting method requires 9 connecting leads in the motor, and the most common voltage is 220/440V, that is,
during the starting, motor is series connected until it reaches the rated speed and then it
is switched to parallel connection.
ELECTRONIC STARTING (SOFT START)