MG.20.B6.02 – VLT is a registered Danfoss trademark
93
VLT
®
2000 Series
Section 1 Section 2 Section 3
Air humidity
The VLT frequency converter has been designed to
meet VDE 0160, 5.2.1.2.
Light dew is tolerated on internal insulating surfaces,
but not during operation.
Efficiency
To reduce energy consumption it is very important to
optimise the efficiency of a system. The efficiency of
each single element in the system should be as high
as possible.
Efficiency of the VLT 2000 Series (
η
VLT
)
The load on the frequency converter has little effect
on its efficiency. In general the efficiency at rated mo-
tor frequency f
M,N
is the same whether the motor
supplies a 100% rated shaft torque or only 75%.
The variable switching frequency affects the losses
in the VLT 2000 Series. The efficiency will drop a little
when the switching frequency is set to a value higher
than 4.5 kHz.
Motor efficiency (
η
MOTOR
)
The efficiency of a motor connected to the frequency
converter depends on the sine shape of the current.
In general efficiency is just as good as at mains ope-
ration.
The motor efficiency depends on the make of the mo-
tor. Normally the motor efficiency drops when the load
is lower than the rated torque.
In the range 75-100% of rated torque the efficiency of
the motor will be almost constant both when
operated by the frequency converter and when
running directly on the mains.
In general the internal switching frequency does not
affect the efficiency of small motors.
System efficiency (
η
SYSTEM
)
To calculate the system efficiency you can multiply the
efficiency of the units of the VLT 2000 Series (η
VLT
) by
the efficiency of the motor (η
MOTOR
) using the below
formula:
η
SYSTEM =
η
VLT x
η
MOTOR
Special conditions
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