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8.29 Calculating the energy saving for fluid flow machines
Overview
Fluid flow machines, which mechanically control the flow rate using valves or throttle flaps,
operate with a constant speed corresponding to the line frequency.
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Figure 8-82 Flow control with pump and throttle connected to a 50 Hz line supply
The lower the flow rate, the poorer the efficiency of the fluid flow machine (pump). The fluid
flow machine (pump) has the poorest efficiency when the throttle or valve is completely closed.
Further, undesirable effects can occur, for example the formation of vapor bubbles in liquids
(cavitation) or the temperature of the medium being pumped can increase.
The converter controls the flow rate by appropriately varying the speed of the fluid flow
machine. By controlling the flow rate, the fluid flow machine operates at the optimum
efficiency for each flow rate. This situation means that in the partial load range less electric
power is required than when controlling the flow rate using valves and throttles.
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Figure 8-83 Flow control with pump and converter
Function description
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The converter calculates the en‐
ergy saving from the flow charac‐
teristic associated with a mechan‐
ical flow control and the meas‐
ured electric power that is drawn.
The calculation is suitable for cen‐
trifugal pumps, fans, radial and
axial compressors, for instance.
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Advanced commissioning
8.29 Calculating the energy saving for fluid flow machines
Distributed converter for SIMOGEAR geared motors
340
Operating Instructions, 10/2020, FW V4.7 SP13, A5E31298649B AL