The discussion focuses on powering a 3.5kW, 50Hz, 4-pole asynchronous induction motor driving a 2.7-tonne screw-type car lift using a 7.5kW rotary phase converter supplying 415Vac 3-phase from a single-phase 240Vac source. The motor stalls lifting heavier loads due to phase voltage imbalance and low power factor (0.65), with one phase dropping from 415V to 350V under load. Proposed solutions include installing a 3-phase to 3-phase VFD to improve phase balance, provide V/F control, torque boost, and enable speed control to reduce mechanical loading. Additional measures involve power factor correction capacitors (~38µF per phase), mechanical lubrication improvements with extreme-pressure grease, and potential loosening of mounting screws to reduce friction and misalignment. The rotary converter’s delta-wound idler motor and transformer setup contribute to voltage imbalance and reactive current issues, which the VFD may partially mitigate but not eliminate.
Electrical engineers, maintenance technicians, and mechanical engineers
It’s better, thanks. You can’t lift halfway, then start again to go higher; the car must be lowered before raising again, to allow the motor a more gradual start. But we did manage to lift it high enough to swap the transfer box, walking underneath comfortably. In fact, this is as high as it will go before hitting the gussets I added to the roof trusses, having cut out the centres.Lnewqban said:Is the lift now able to handle the 2.6 tons RR sport?