Capacitor start circuit for single phase induction motor - has two capacitors dimensioned to satisfy start and run condition with relay responding to rotor acceleration

摘要

A single phase induction motor employs two phase shifting capacitors (5, 6) which collectively satisfy the differing requirements of a start and run condition via the action of a voltage operated relay (13, 14). A star connected motor winding (1, 2, 3) has a start capacitor (5) and auxiliary capacitor (6) connected in series across windings (1, 3). Relay operating coil (14) is de-energised at standstill leaving only capacitor (5) in circuit. As speed picks up, voltage (Uc) increases and relay (13, 14) operates to open normally closed contact (13) and thus insert capacitor (6). The reduced capacity of the combination is dimensioned to promoting a stable balance between full load torque and slip. USE/ADVANTAGE - Does not require customary capacitor switching devices, e.g., centrifugal or timer relays. Gives good performance, reliability and economy.