Alternative to Step-Down Transformer for Induction Motor

If its a standard frame motor it might be easier and cheaper to replace the motor.

...or if not, you can have the motor rewound...

A VFD probably exists that will do the complete voltage and frequency conversion for this motor.

Why did you move this motor halfway around the world to make this problem?

I found electric garden tiler only available in US so far. That was 6 years ago. Even today there is none in whole Australia, and I am not sure if anywhere else do such thing at 220-240V.

Single or three_phase transformer ? See-for instance:

https://www.amazon.com/KRI%C3%8BGER-Voltage-Transformer-Converter-Approved/dp/B00HDVIHIG?ref_=fsclp_pl_dp_2

In a word, no. 120V means it is a single phase motor, probably with a Capacitor Start type based on the application. That type of motor is incompatible with any electronic solution, you would just set up a race to see which component fails the fastest.

Just replace the motor with something local.

You are probably correct that it is a single phase motor but I have seen 3 phase, 120 volt motors. We had one on a hydrogen meter for a hydrogen cooled generator. Also most modern automatic washing machines use a 3 phase 120 volt motor to avoid using gear boxes. With a VFD the same motor runs at low speed (direct drive) for agitation (reversing) and at high speed for spinning.

For around $110 AUD you can buy a 750W 240V 1440RPM single phase motor so why mess around with capacitors etc.

If you were to try a thyristor then it has to be symetrical in its triggering else any asymetric part of the waveform will appear as a DC to the motor and either cook it or saturate the windings and with the small motor DC resistance it doesn't take many volts to give quite a bit of current.

Check inside the motor terminal box it may just be able to be reconnected as 110/220V but then it will run slower for USA have 60Hz not 50Hz as here in Aus.

As has been noted elsewhere, a replacement motor would be the better choice, but purely as a thought exercise - and I'm only guessing as I have never tried it, but would a heavy duty resistance (thinking the element of a 120V heater) connected in series achieve the desired result? Possibly 2 x 240v elements in parallel and then in series with the motor if you can't find a 120v one

Certainly would not be power efficient, but that wasn't one of the parameters in your question.

I did use a slightly similar thing (the old wire wound ceramic elements) many years ago when I made some DC injection systems for 3 phase dough brakes in a bakery to prevent the staff being dragged into the rollers.

Not a good idea. Assuming it is an induction motor since at start up it draws about 7 times running current it would have very low voltage available at start (probably would not start) relatively but high voltage when it reached speed. Say running current is 8 amp at 120 volt so you use a 1,000 watt 120 volt heater in series. At start it would have about 30 volts and heater would have about 200 volt. Motor probably would not start and heater would probably burn out. Sat 5,000 watt (or 5 each 1,000 watt in parallel). At start motor would have about adequate voltage but when it reached speed it would have about 190 volts and probably fail soon. The voltage divider idea works with constant resistances but motor has much more" resistance" (or reactance or effective resistance)at speed than at start.

A Variac if available may help you achieve your wishes.. It is a variable autotransformer used in the olden days as dimmers, motor controller..

A transformer is like $170 US ?

https://www.automationdirect.com/adc/shopping/catalog/power_products_(electrical)/transformers/1-phase_encapsulated_transformers_(nema_rated)/480x240_vac_to_240x120_vac/c1f1c0les

I see a section of electric tillers on eBay Australia. This one is $250 AU and designed for your power grid.

SPECIFICATIONS

Does your 240 volt supply carry a neutral,which is a center tap on the supply transformer from the utility?

Do you have any 120 volt appliances in your home?

If so,use one hot leg of the supply and the neutral to obtain the 120 volts.

Test your voltage from hot to neutral to determine what you have.

Be certain to install the appropriate short circuit (fuse or circuit breaker) as appropriate for the conductor,and protection device for the motor as well.

Search Google for a 1 KVA transformer.That will be sufficient for your purpose.

I have seen some,but they will not ship to Oceana,but there are sure to be some in your area.The ones I have seen are about $50.00 US.,good used ones even cheaper.

They should weigh around 23 pounds.

Get one that is NEMA 3R (outdoor) rated and mount it outside with a receptacle added for your tiller.

Just replace the motor. "Simples ξ".