Fairford Electronics QFE Series, Руководство пользователя

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QFE
page 3-21
Applications
FD841405_F
3.4.5 How Much Energy?
The amount of energy used by a squirrel cage induction motor operating with a soft starter in
energy-optimising mode is shown in the following Figure, for the same duty cycle as Fig.
3.4.1.2. By reducing the voltage when torque demand is below maximum, the magnetising
current is proportioned to the torque current.
Compare Fig. 3.4.5.1, energy-optimising, with Fig. 3.4.1.2, non-optimising. (These graphical
representations are illustrative only and not to scale.) To arrive at any exact figure for the
energy saved requires each individual case to be examined in detail, taking into account the
motor rating, type, and any special characteristics, Load, load characteristics, duty cycle,
supply voltage, supply authority tariffs and the user’s particular terms.
Fig 3.4.5.1 Energy savings
The calculations to cover all the likely or possible conditions would be laborious. An empirical
method for arriving at a usefully realistic estimate has been devised by Fairford Electronics Ltd.
Used with a proper sense of engineering circumspection, the following tables allow a user to
gain a reasonably close estimate of the saving to be achieved within the motor by using The
QFE optimising soft starter. The method does not include any additional savings and benefits
conferred by other sources, such as -
Reduction of heating losses in cabling because of the lower voltages;
Potential reduction of maximum demand charges;
Further energy saving and other benefits deriving from the soft starting process itself
Reduced
total energy-demand,
reduced wear and tear,
reduced maintenance and replacement costs.
100
50
40 60 80 100 120 140 160
%
FLC
0
seconds
Magnetising current
Torque current