How can amps and frequency of currents be changed

[onetwothree4]

Hello again asking many question lately!( got more)[Thankyou all for your answers and advice]


So here (Australia) the mains power comes out at around 50hz and 15amps 240vac for example

and that goes to power smaller devices that work at maybe lower hz , amps and voltages what/how can that higher quantity be lowered?
( does it also work for DC as well?)

what electronic components would do that job? (triac,transformers,resistors,scrs,capacitors..etc)



You can probably control the amount of current you need just with a specified voltage and resistance using ohms law but how can it be done with only a pre determined source?

 

[alec_t]

A transformer can lower mains voltage safely. It cannot work with DC. A plug-in mains adapter includes a transformer (working at either mains frequency or tens of kHz) and can output AC or DC (depending on type) at a lower voltage.
Whatever gadget you have is designed to work with a rated voltage and, because of its inherent resistance, will draw a rated current determined by (among other things) Ohm's Law.
Your mains supply can provide as much current as your gadgets call for (up to a maximum amperage determined by the mains wiring thickness, hence resistance and hence ability to carry current without overheating). A fuse or circuit-breaker will limit current to a safe level.

 

[onetwothree4]

Thanks for that information alec_t
still other question that puzzle me
what i was trying to say is that

If i was trying to MAKE a circuit on my own
to change the frequency,voltage and current on ac and dc(not frequency for dc) power how would go about doing that?

Like i have a primary power source of 70 hz 15amp 240vac and i want to lower/increase the values of (hz , amp, volt)

for example to power a light bulb that only works with 70hz 5amp 60 vac , with electrical components what can i build with them to lower the values

 

[Nigel Goodwin]

Thanks for that information alec_t
still other question that puzzle me
what i was trying to say is that

If i was trying to MAKE a circuit on my own
to change the frequency,voltage and current on ac and dc(not frequency for dc) power how would go about doing that?

Like i have a primary power source of 70 hz 15amp 240vac and i want to lower/increase the values of (hz , amp, volt)

for example to power a light bulb that only works with 70hz 5amp 60 vac , with electrical components what can i build with them to lower the values

Essentially you DON'T change the frequency, there's almost never any need to do so - and there's no such thing as a 70Hz bulb.

Voltage and current are easy, you simply use a correctly rated transformer to change the voltage, the current is dependent on what the load wants - and you specify the transformer to be capable of it.

Frequency can be done, but it's not simple, and far beyond anyone who has to ask.

 

[profbuxton]

Where are you getting this "primary power source" at 70Hz from?. Australian power systems supply mains power at 50 Hz 240v single phase and 415v three phase.
Lights bulbs do not care about Hz only the voltage. If you want to light it up you will need a transformer 240 primary/60v secondary rated at 300VA. Power = volts x amps.

 

[onetwothree4]

Thank you Nigel and profbuxton for your replies.

Nigel if i can't find a transformer that fit my needs can how do i build a circuit that can change voltage down.{I want to make one myself and i want to know what and every component does to add to the lowering of the voltage}

You know how on hand drill they can change their speed and on some vacuum cleaner they can also change speeds as well as celling fans.

I Want To Understand the Fundamentals as on How those circuits work so i can build one on my own without the need for a pre-made schematic

for instances **broken link removed** this is the schematic for motor speed/voltage control. I could just build that circuit

But i want to understand how and what everything that was used to lower the voltage did to contribute.

:/ do you know the means of how to change the frequency of ac Nigel? my grandpa said the same thing but i don't care how complicated it is i want to know

 

[cowboybob]

https://en.wikipedia.org/wiki/Frequency_changer

Follow the various links to get addition information.

 

[Nigel Goodwin]

Thank you Nigel and profbuxton for your replies.

Nigel if i can't find a transformer that fit my needs can how do i build a circuit that can change voltage down.{I want to make one myself and i want to know what and every component does to add to the lowering of the voltage}

You know how on hand drill they can change their speed and on some vacuum cleaner they can also change speeds as well as celling fans.

I Want To Understand the Fundamentals as on How those circuits work so i can build one on my own without the need for a pre-made schematic

for instances **broken link removed** this is the schematic for motor speed/voltage control. I could just build that circuit

But i want to understand how and what everything that was used to lower the voltage did to contribute.

:/ do you know the means of how to change the frequency of ac Nigel? my grandpa said the same thing but i don't care how complicated it is i want to know

We can't give you five years of college training in a forum post - you don't know the simple basics, so it's not possible to explain things to you.

This is emphasised even more by your 'variable voltage' suggestions for speed control, that's not how it works, and there's various ways used depending on the specific motor types.

As far as transformers go, you either find one that does what you want, wind one yourself, or have one wound professionally.

 

[audioguru]

I think there is a 70Hz mains in some third world countries where they use donkeys pushing around the armature of an multi-pole alternator and the donkeys have recently been fed. When the donkeys get tired or hungry then the mains frequency drops to 30Hz or 40Hz.

 

[tcmtech]

Using a common 115/230:230/460 power transformer with your 240 VAC being fed to the 460 VAC windings would give you 60 VAC on the 115 VAC output.

Being you would be running the transformer at half its normal voltage you would need one of double the VA rating of the load so if your load was 500 VA/watts you wold need a 1000 VA/watt rated transformer.