Danfoss VLT AutomationDrive FC 302 Design Guide

FC 300 Design Guide
How to Select Your VLT
" Efficiency
To reduce energy consumption, it is very important
to optimize the efficienc y of a system. The
efficiency of ea ch single element in the system
should be as high as possible.
Efficiency of FC 300 Ser ies (η
VLT
)
The load on the adjustable fre quency drive has little effect on its efficiency. In g ene ral, the
efficiency is the same at the rated motor frequency f
M,N
, even if the motor supplies 100%
of the rated shaft torque o r only 75%, i.e. partial 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 motor.
There is a slight decline in efficiency when the sw itching frequency is set to a value ab ove
5 kHz. The rate of efficiency w ill also be slightly reduced if the mains voltage is 500 V,
or if the motor cable is longer tha n 100 ft (30 m).
Efficiency of the mot o r (η
MOTOR
)
The efficiency of a motor connected to the ad justable frequency drive d epends on the sine
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 e ffici ency of the motor is practically constant, both
when it is controlled by the adjustable frequency drive and when it runs directly on mains.
In small motors, the influence of the U/f characteristic on efficiency is margina l. How ever, in
motors from 15 HP (11 kW) and up, the advantages are significant.
In general, the switching frequency does not affect the efficienc y of small moto rs. Motors from
15 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 efficiency of FC 300 Series (η
VLT
) is multiplied
by the efficiency o f the motor (η
MOTOR
):
η
SYSTEM
)=η
VLT
x η
MOTOR
Estimate the efficiency of the system at diffe rent loads based on the graph above.
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MG.33.B3.22 - VLT is a registered Danfoss trademark

Danfoss VLT AutomationDrive FC 302 Specifications

General

Brand	Danfoss
Model	VLT AutomationDrive FC 302
Category	DC Drives
Language	English