VLT® 5000 Crane
Appendix
■
Air Humidity
VLT 5000 Crane has been designed to meet the
IEC 68-2-3 standard, EN 50178 pkt. 9.4.2.2/DIN
40040, class E, at 40°C.
■
Efficiency
Efficiency of VLT 5000 Crane (
η
VLT
)
The load on the frequency converter has little effect on
its efficiency. In general, the efficiency is the same at
the rated motor frequency f
M,N
, regardless of whether
the motor supplies 100% of the rated shaft torque
or only 75%, i.e. in case of part loads.
Efficiency of the motor (
η
MOTOR
)
The efficiency of a motor connected to the frequency
converter depends on the Wave shape of the
current. In general, the efficiency is just as good
as with mains operation. The efficiency of the
motor depends on the type of motor.
In the range of 75-100% of the rated torque, the
efficiency of the motor is practically constant, both
when it is controlled by the frequency converter
and when it runs directly on mains.
In general, the switching frequency does not affect
the efficiency of small motors. Motors from 11 kW
and up have their efficiency improved (1-2%). This
is because the sine shape of the motor current is
almost perfect at high switching frequency.
Efficiency of the system (
η
SYSTEM
)
To calculate the system efficiency, the efficiency
of VLT 5000 Crane (
η
VLT
) is multiplied by the
efficiency of the motor (
η
MOTOR
):
(
η
SYSTEM
) =
η
VLT
x
η
MOTOR
MG.50.N4.02 - VLT is a registered Danfoss trademark
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