Danfoss FC 300 Design Guide

FC 300 Design Guide
FC 300 Selection
" Efficiency
Efficiency of FC 300 Series (η
VLT
)
The load on the adjustable fre quency drive has little effect on its efficiency. In general, the
efficiency is the same at the rated m otor frequency f
M,N
, even if the motor supplies 100% of
the rated shaft torque or only 7 5%, i.e., in case of part loads.
This also means that the efficiency of the adjustable frequency drive does not cha nge
even if other U/f characteristics are chosen.
However, the U/f characteristics influence the efficiency of the m otor.
The efficiency declines a little when the switching frequency is set t o a value of above 5 kHz. The efficiency
will also be slightly reduced i f the line voltage is 500 V, or if the motor cable is longer than 98.43 ft. [30 m].
Efficiency of the motor (η
MOTOR
)
The efficienc y of a motor connected to the ad jus table frequency drive depends on magnetizing lev
el. In general,
the efficiency is just as good as with line operation. The efficiency of the motor depends on the type of motor.
In the range of 75 -100% of the rated t orque, the efficiency of the motor is practically constant, both when
it is controlled by the adjustable frequency drive and when it runs directly on line power.
In small motors, the influence from the U/f characteristic on efficiency is marginal. Howe ver, in
motors from 14.75 HP [11 kW] and up, the advantages are significant.
In general, the switching frequency does not a ffect the efficienc
y of small motors. Motors from
14.75 HP [11 kW] and up have their efficiency improved (1-2%). This is because the sine shape
of the m oto r current is almost perfect at h igh switching frequency.
Efficiency of the system (η
SYSTEM
)
To calculate the system efficiency, the FC 300 Series efficienc
y(η
VLT
)ismultiplied
by the efficiency of the motor (η
MOTOR
):
η
SYSTEM
)=η
VLT
x η
MOTOR
Calculate the efficiency of the system at different loads based on the graph above.
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MG.33.B6.22 - VLT is a registered Danfoss trademark

Danfoss FC 300 Specifications

General

Brand	Danfoss
Model	FC 300
Category	DC Drives
Language	English