Direction Of Rotation; Star Or Delta Motor Connection; Multi-Motor Connection; Motor Overload Protection - Siemens Midimaster Eco Reference Manual

DIRECTION OF ROTATION

The direction of rotation of the motor can be
reversed during commissioning by changing over
two of the output connections on the Eco.
STAR OR DELTA MOTOR
CONNECTION
The MICROMASTER Eco & MIDIMASTER Eco
range can be used to control all types of three-
phase asynchronous squirrel cage motors.
The voltage and connection method should be
taken from the motor nameplate, but as a general
rule, larger motors (380/660 volt) are delta-
connected and smaller motors (220/380 volt) are
star-connected.
U V W
Z X Y

MULTI-MOTOR CONNECTION

The MICROMASTER Eco & MIDIMASTER Eco
range can be used to control several motors
connected in parallel.
If the motors to be controlled are to run at different
speeds from one another, then motors with
different rated speeds must be used. Because
motor speeds will change simultaneously, the
10-8
PE U V W
x x x x
M
PE U V W
x x x x
M
U V W
Z X Y
ratio between the rated motor speeds will be
consistent over the full range.
If motor sizes vary to any great extent, this could
cause problems at start-up and at low rpm. This is
because smaller motors need a higher voltage
during start-up, as they have a higher resistance
value in the stator.
Additional motor protection (e.g. thermistors in
every motor or individual thermal overload relays)
is essential in systems with parallel motor
operation. This is because the inverter's internal
thermal protection cannot be used, as output
current must be programmed to match the overall
motor current.
Total motor current consumption must not exceed
maximum rated output current.
Parameter P077 should be set to multi motor
mode.

MOTOR OVERLOAD PROTECTION

When operated below rated speed, the cooling
effect of fans fitted to the motor shaft is reduced,
so that most motors require de-rating for
continuous operation at low frequencies.
However, variable torque loads such as pumps
and fans are generally not heavily loaded at low
speeds. To provide motors with additional
protection against overheating, a PTC (thermistor)
temperature sensor may be fitted to the motor and
connected to the inverter control terminals. Note:
to enable the motor overload protection trip
function, see parameter P087=1.

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ECO REFERENCE MANUAL
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