According to the present invention, in a water supply apparatus which converts
output power of a solar cell with an inverter to drive a motor pump for pumping
up water, a DC brushless motor having no sensor for detecting a position of a rotatable
shaft is used as a motor for driving the pump. Further, the water supply apparatus,
having a pump and a frequency converter for supplying electric power to the pump
and controlling a rotational speed of the pump, includes a standard current value
table in which rotational frequencies of the pump and standard current values as
criteria for shutoff operation at the rotational frequencies are associated with
each other, a rotational frequency detecting device for detecting a rotational
frequency of the pump, a standard current value acquiring device for acquiring
a standard current value corresponding to the rotational frequency detected by
the rotational frequency detecting device with reference to the standard current
value table, a current detecting device for detecting a current value supplied
to the pump, and a comparing device for comparing the current value detected by
the current detecting device with the standard current value acquired by the standard
current value acquiring device.
