To provide a controller capable of stopping a pump at a minimum flow rate without using a flow switch in a direct feed-type pump water supply device.
The relationship of f=aΔP2+bΔP+c is established between the differential pressure ΔP obtained by subtracting the suction pressure from the pump discharging pressure, and the frequency (f) of a variable speed gear. The frequency fmin in a minimum flow rate is determined by substituting ΔP, and the frequency of the pump is reduced for a predetermined time when the relationship with respect to the actual frequency (f) becomes f<fmin. The control device has a control means for increasing the frequency by the feedback control in a high flow rate as the pressure is lowered, and continuously decreasing the frequency in a low flow rate as the pressure is not lowered, and stopping a pump by making the frequency 0 at the frequency below a predetermined value.
SHIMOKAWA SEIJI
YASUNAGA TAMIYOSHI
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