2-76 Economizer
Economizer Auto-Economizer (also see Torque Performance Modes on page 2-162)
Economize mode consists of the sensorless vector control voltage with an
energy saving function (E-SVC).
The output voltage is automatically adjusted, in steady state frequency
operation only, as the load is increased or decreased such that minimum
current is supplied to the motor and its efficiency is optimized. Adjusting
the flux producing current facilitates reduction of the output voltage. The
flux current is reduced as long as the total drive output current does not
exceed 75% of motor rated current. The flux current is not allowed to be
less than 50% of the selected flux current parameter value.
Efficiency The following chart is typical of the efficiency calculations for variable
frequency drives. Efficiency generally decreases with increasing load on
decreasing speed.
Maximum Voltage
Maximum
Frequency
Frequency
V
total
Motor Nameplate Voltage
Motor Nameplate
Frequency
Ir Voltage
0
0
Rated Flux Current
Reduced Flux Current,
minimum of 50% of Rated Flux Current
Increasing
Load
25 50 75 100
1 HP
0.5 HP
0.5
0.6
0.7
0.8
0.9
1
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