| 摘要 |
PURPOSE:To enable to positively control air-fuel ratio by a simple structure, by controlling an electric motor according to the forced air rate which is determined by multiplying a detected value of fuel flow rate by a predetermined air- fuel ratio, in an apparatus using a variable-speed motor for a forced draft fan driving motor. CONSTITUTION:When a forced draft fan 6 which is driven by a variable-speed motor 8 is controlled, first, the fuel flow rate to a boiler during operation is detected by a flow rate detector 30, and the value is put into a fuel flow rate detecting circuit 25 to find an actual fuel flow rate FF. Next, the actual fuel flow rate FF is put into an air flow rate calculating circuit 27, and an air flow rate FA is calculated by multiplying the input rate FF by the air-fuel ratio alpha being set in an air-fuel ratio setting circuit 26. The air flow rate FA is put into a speed setting circuit 28, and is applied to an inverter 24 after it is converted into a speed signal in proportion to the flow rate FA, thereby, the variable- speed motor 8 can be controlled. |
