Variable Speed Motor

I need some help to find out what i need to buy to end up with a single phase motor that i can adjust its speed from 0 to max 1485rpm. Budget is tight so i am looking to buy a used motor to keep the costs down.

Size of the motor won’t be more than 1kW. I had a look online and there are lots of single phase motors and some cheap type speed controllers (£15). 

Is this all i need? Does the motor need to be of a specific type? I noticed some motors have a capacitor on the outside, can these still be used for such an application?

I would think that the real difficulty will be having a very low speed with any significant power if you really want to control from zero up.

I assume you are looking at thyristor / triac controllers, which work by switching part of the sine wave. I believe you will want a universal type motor, i.e. brushes and commutator.

What will you be running with this motor? At low speeds you will not get a lot of torque which may cause you problems.

why not get a 3 phase motor and an inverter?

Thanks for the replies chaps,

I will use the motor on a belt conveyor which at the moment it’s operated by a manual lever and chain mechanism, around 20rpm manually.

i am looking to automate it with the option to run it a bit faster or slower as necessary.

i can’t see me needing much of torque for this application but it definitely needs to be a really slow process, 20rpm is the ideal speed.

I prefer a system that won’t consist of many electronics, especially inverters or heavy three phase motors. The conveyor will be stored outside (covered) so inverters and many electronics is not a good idea...

TBH gearing down would probably be easier and cheaper.

IP65 inverter, & motor problem solved.

Sidewinder said:

IP65 inverter, & motor problem solved.

Click to expand...

any single phase AC motor with any inverter will do the job?

How big is the conveyor? What is the conveyor load? How fast do you want to accelerate the conveyor?  Do you want the conveyor to position? Do you want the conveyor to be braked by the motor?

mecheng46 said:

any single phase AC motor with any inverter will do the job?

Click to expand...

three phase motor will work with an inverter on a single phase supply

Sidewinder said:

How big is the conveyor? What is the conveyor load? How fast do you want to accelerate the conveyor?  Do you want the conveyor to position? Do you want the conveyor to be braked by the motor?

Click to expand...

3m long conveyor

20kg of load when full

20rpm

no need to position

no need to have brakes

It needs to be single phase (no access to 3 phase), as small as possible, simple and cheap design without many electronics.

To size a motor to a conveyor I would need much more detail on the dimensions than 3m long.

My mistake I should have asked for “All of the dimensions & specifications of the conveyor?” Rather than “How big is the conveyor?”

If you want reliable speed control you are going to have electronics.

Is this a DIY job or for use in a business or money making enterprise in any way?

mecheng46 said:

It needs to be single phase (no access to 3 phase), as small as possible, simple and cheap design without many electronics.

Click to expand...

the motor can be 3 phase if running from an inverter on a single phase supply

Sidewinder said:

To size a motor to a conveyor I would need much more detail on the dimensions than 3m long.

My mistake I should have asked for “All of the dimensions & specifications of the conveyor?” Rather than “How big is the conveyor?”

If you want reliable speed control you are going to have electronics.

Is this a DIY job or for use in a business or money making enterprise in any way?

Click to expand...

this is for a diy job. As it stands i operate the conveyor my self with a manual lever, nothing fancy other than a lever, a chain and two sprockets and i am looking to automate it. Years ago i used to have a motor in the garage that has a manual lever sticking out from the back and it had 3 settings, 3 different speed settings. The motor was a single phase 240v motor. The motor went ages ago and since then i never came across anything similar, this might be the solution to this conversion i am trying to do. With the right gearing i can adjust it to suit my needs.

Does anybody have an idea what type this motor was? Vintage motor, manual lever at the back with a plastic round head, 3 different slots, 3 different speed settings, single phase, 240v AC