Stepping down 240vac to 100-80vac without or without a transformer

[onetwothree4]

Hello peoples, I have had problems with a vacuum cleaner motor and have tested with other pre-built potentiometer circuits that lower voltage from scrap components but all was a fail; there was still too much voltage. Is there any other way I can make a circuit of my own that could step down voltage?

I am not even quite sure what the parts of the scrap components are for( always seems to contain capacitors and resistors)
I have tried to use the parts from a vacuum cleaner and a hand drill

Can someone please explain and tell me how I could make a circuit of my own?

 

[Reloadron]

You don't mention the current requirements? You also don't mention the Frequency? Stepping a voltage up or down isn't difficult but depending on the current and frequency requirements there are several ways to go about it. While living in Italy for 3 years I ran several US 120 VAC 60Hz appliances on the 240 VAC 50Hz Italian power using a transformer but those appliances were able to run on the 50 Hz power. How you can do it depends on your power requirements.

Ron

 

[Nigel Goodwin]

Can someone please explain and tell me how I could make a circuit of my own?

You need to explain EXACTLY what you're trying to do, and why! - it's much too vague so far.

 

[Cicero]

I found that OP post quite cryptic, but a properly rated transformer is the best method of stepping down an AC voltage and safer. Not sure what kind of potentiometer circuits you were trying to use but it sounds scary.

 

[onetwothree4]

Sorry for the unclear post, I will try to explain in more detail.
I am building a disc sander and I have gone with using a vacuum cleaner motor to spin the disc .

The problem is that the motor spins too fast at the start when the power is turned on and the disc isn't able to grasp the axial of the motor
so I need the motor to spins slowly at the start and gradually speed up.

( Was wondering if it is possible to create a circuit that could output varies lower voltages from 240 vac, like an autotransformer or a rheostat)

I live in Australia so the mains electricity is around 240-230vac (15amps)(50Hz)
I wasn't able to include any details about the requirements for the motor to run I couldn't find anything[ I think it will run with just the voltage stepped down but the current and frequency the same]





basically I want a variable voltage supply ( but I don't know how to it work or how to make one)

 

[onetwothree4]

I found that OP post quite cryptic, but a properly rated transformer is the best method of stepping down an AC voltage and safer. Not sure what kind of potentiometer circuits you were trying to use but it sounds scary.

If I were to use a transformer, would it be as simple as taking the wires out of the metal case and rewinding new wires as the secondary coil? I have transformers of different sizes does that matter as well?

 

[Cicero]

If I were to use a transformer, would it be as simple as taking the wires out of the metal case and rewinding new wires as the secondary coil? I have transformers of different sizes does that matter as well?

No, I posted before I knew what you were doing

I think you need something like this... **broken link removed**

But I'm not sure it'll give you the slow enough start you want still. Could you find the specs of your motor maybe?

 

[tunedwolf]

I think I would have scrapped the washing machine instead

 

[alec_t]

The problem is that the motor spins too fast at the start when the power is turned on and the disc isn't able to grasp the axle of the motor

If the disc slips on the shaft at start-up you need to modify the coupling so that it doesn't slip. Otherwise, as soon as you apply pressure on the workpiece to start sanding, even when using a reduced voltage, you will still have a slippage problem. Cure the slippage and you won't need to reduce the voltage.
If your electronics knowledge is limited, building a speed control operating at mains voltage without a properly rated isolation transformer is not recommended. Any error could be fatal .

 

[ronsimpson]

I don't know if this will solve the problem. It is a variable voltage transformer. There is a big know on top to adjust the output voltage.

 

[onetwothree4]

No, I posted before I knew what you were doing

I think you need something like this... **broken link removed**

But I'm not sure it'll give you the slow enough start you want still. Could you find the specs of your motor maybe?

This is the stuff! That is what I want to make. Sorry to trouble you more, but may you please explain how all that works? how does the 240vac go through all those components and get to lower voltages?

I might follow the schematic and make a the circuit but if the voltage is still too much I just want to know to to step it down a bit more.

[ This only work for induction motors?, is a vacuum cleaner motor an induction motor?]

 

[Reloadron]

A Google of "lamp dimmer circuit using triac" will bring up dozens of circuits broken link removed along the lines of the posted circuit. If a motor load is light enough in many cases a simple lamp dimmer capable of a 600 watt load will control the motor speed but... you need to know the motor's ratings and the motor type. Vacuum cleaner motors are not all the same. You need to know exactly what you have.As to these circuits (lamp dimmers) they are more often cheaper and easier to buy off the shelf than build, they are generally very inexpensive.

Ron

 

[onetwothree4]

A Google of "lamp dimmer circuit using triac" will bring up dozens of circuits broken link removed along the lines of the posted circuit. If a motor load is light enough in many cases a simple lamp dimmer capable of a 600 watt load will control the motor speed but... you need to know the motor's ratings and the motor type. Vacuum cleaner motors are not all the same. You need to know exactly what you have.As to these circuits (lamp dimmers) they are more often cheaper and easier to buy off the shelf than build, they are generally very inexpensive.

Ron

Seems like a good idea ! I will give it a try

 

[Cicero]

Have a look at this. https://www.bristolwatch.com/ele/triacs.htm

It works by varying the how much of the AC waveform is allowed over the motor/load. It does this using a triac which is essentially an AC switch, that will only switch on when it gets a voltage on its gate above a certain level. That gate voltage is the capacitor voltage, and the time it takes to reach the trigger voltage is varied by adjusting the potentiometer. If the speed is not slow enough, which I suspect it may not be, you can also try using an SCR instead of a triac. It'll cut out one half cycle completely and drop the power even more. Baring in mind this will affect the available max speed, but that may not be a problem, and even then there are easy ways around this.

 

[onetwothree4]

Looks like some pretty good stuff Cicero, I will see what I can do ,kind of short on parts don't know where to buy electrical hardware over here
Thank you and everyone here for your helps!

 

[schmitt trigger]

Vacuum cleaner motors are usually series-wound universal ones.
Series-wound motors will over speed without a mechanical load. They may reach dangerous speeds.

Anyways if you decide to use one, use a Triac light dimmer.

 

[MikeMl]

Vacuum cleaner motors are usually series-wound universal ones.
Series-wound motors will over speed without a mechanical load. They may reach dangerous speeds...

I refer you to this which I posted here in 2009.

Happy new Year!