Electrical control of central heating pump speed - is by auxiliary impedance with temporary short-circuit for motor starting

摘要

The auxiliary impedance (1) is in series with at least part of a main or auxiliary phase of the capacitor motor which drives the pump. At starting, the temp. dependent resistance (8) in parallel with this auxiliary impedance is effectively a short-circuit or bypass so that the motor developes its max. torque. After a short interval the resistance (8) becomes heated and comparable with an open circuit. The impedance (1) then assumes effective control. It is pref. variable so that the low-speed setting of the pump can be adapted to the characteristics of the particular installation.. The max. starting torque is achieved repeatably without resort to an artificially heated bimetal strip or a costly and bulky electromagnetic relay for bypassing the control impedance.