Phase Protection for 1 phase induction AC motor

No telling what could be wrong here....but you probably can't alter an ADA certified machine...

https://www.discovermymobility.com/store/wheelchairlifts/lift-avator/veri-lift/index.html

well, its not ADA approved I guess. They copied the outlook. But so unsafe for a hydraulic plunger with single phase induction motor used with a reversible hydraulic pump.

This I think is the original design

Well to do a proper job, and two things come to mind either the lift is being overloaded, or proper maintenance has not been followed, so in either case I would check the amp draw to see if the motor/pump is being overloaded....It could be it just need greasing, if it's not over drawing amperage, then it's likely that it's an electrical failure, or possibly a mechanical failure...so you need to know the age, if it's like 15-20 years old you need to start replacing parts, or get a new one....If the lift operates properly with no load, then it has just lost some capacity...has it been greased regularly? If not then some parts may have suffered excessive wear and need to be replaced...

This drawing shows a lead-screw design - not the hydraulic system you described. If this is your system, look for a control board with SCRs or other electronic parts that may be malfunctioning. If it's just a motor and switches, and there is a starting capacitor, that may be bad. I doubt seriously if it's a shaded-pole motor.

https://www.sqone.com/electric-motor-types/definite-purpose-motors/elevator-motors

https://www.sqone.com/us-motors-d34arm2ncr

I have no malicious motives by the way,other than public safety and design improvement.

It's the faulty way the shaded pole motor has been produced. If the shaded pole does not produce enough magnetic flux, the squirrel cage rotor does not advance in the correct direction.

It definitely sounds like that motor is being overloaded. In any case, the following is valid.

If it is indeed a hydraulic cylinder system, Then a one-way flow restrictor installed in the feed line at the bottom of the cylinder would prevent rapid descent. This would allow full flow into the bottom of the cylinder, but limit the flow out of the bottom of the cylinder.

In a quick search, I failed to find a single device that would do the job for hydraulic fluid, although I'd think it ought to be made. SE could probably find one in a minute or two... There are a number of such devices for air.

There definitely are check valves and flow restrictors, so one of each plumbed in parallel would work if necessary.

There is a 50% chance that a <...1 phase induction AC motor...> will start in either direction unless there is a starting winding and associated capacitor available to start it in the desired direction.

The only way to determine whether such a <...motor...> is turning in the correct direction is either to observe it or to measure it with some sort of direction detection equipment.

If there is a start winding and a capacitor present then the possibilities for misbehaviour include:

• start winding open circuit
• start capacitor open circuit
• aftermarket start capacitor capacitance too small
• start switch open circuit
• etc.

If in doubt, consult a qualified local Electrician.

There is no “phase protection” for a single phase motor, because there is only one “phase”, and is does not change, so there is nothing to protect against.

If you have a single phase motor that does not always start in the correct direction, something is wrong with the motor or, if it is a reversible single phase motor, then something is wrong with the device that controls which direction it is to run. Look at the controller and if that is in good condition, it’s the motor and rather that try to find out what and fix it, it is ALWAYS less expensive to just replace it.

Perhaps electric check valves appropriately installed on the hydraulics,or diodes, likewise.

Send me a copy of the schematics,hydraulic and electrical and I may be able to help with the control strategy.

If the motor has a centrifugal switch,the OL may occur before the switch has time to open,causing the pump to continue in the same direction but the hydraulic would be reversed by control strategy.This would result in a power-applied downward motion,with no delay between directions.

In this case,a reversing relay would possibly solve the problem.

More info required.