Using Step Down Transformer.

[alex.flory]

Hi All,

I am not an electronic person. I was looking for some info on step down transformer and found alot of info in the net but none has satisfied what I need to know. So any help is appreciated.

I need to use a step down transformer to power a CNC controller. If you don't know what CNC is basically it is a unit to control a set of stepper motors for machining works.

So I have a switching power unit that has an output of 24V and 6.3A. But it needs a 120V main supply. My main is 240V. Thats where the step down transformer comes in. I saw one in the shop with the following rating.

200w
240 to 120V
1.8A peak output.

If the peak output of this transformer is only 1.8A, can i connect the switching power unit to the transformer and still get the max output of 6.3A?

Thanks in advance.

Alex

 

[pico]

Yes, youcanuse this step-down transformer for your CNC controller.
Youcan calculate by using the simple electrical power formula.

Power (Watt or W) = Voltage (Volt or V) * Current (Ampere or A)
The sign * means multiply

For your case.
Your CNC controller need power = 24V * 6.3A = 151.2W. Calculate back to 120V it need the cuurrent = 151.2W/120V = 1.26A
The step-down transformer can supply power up to 200W (At the output of 120V, the cuurrent is 200W/120V = 1.66A and it can handle output peak current up to 1.8A)
Hope this can help.

 

[dipal_z]

I feel you should be able to use it because input power (VxI) = 120x1.8 = 216 is greater then required power i.e. 24x6.3 = 151.2. However i am not considering power factor into account, may be some one else will be able to correct the formula for power factor consideration.

 

[alex.flory]

Yes, youcanuse this step-down transformer for your CNC controller.
Youcan calculate by using the simple electrical power formula.

Power (Watt or W) = Voltage (Volt or V) * Current (Ampere or A)
The sign * means multiply

For your case.
Your CNC controller need power = 24V * 6.3A = 151.2W. Calculate back to 120V it need the cuurrent = 151.2W/120V = 1.26A
The step-down transformer can supply power up to 200W (At the output of 120V, the cuurrent is 200W/120V = 1.66A and it can handle output peak current up to 1.8A)
Hope this can help.

I was wondering whether there was a formula to take into account of the lower amperage of 1.8A from the output of the transformer. I think your formula make sense. Will do some calculation. If I get a larger transformer with output of 500w and 4.5A, will this be too much or the excess power will be just a reserve?

I feel you should be able to use it because input power (VxI) = 120x1.8 = 216 is greater then required power i.e. 24x6.3 = 151.2. However i am not considering power factor into account, may be some one else will be able to correct the formula for power factor consideration.

Thanks for the info. If anyone else can add a few more comments, I think I am good to go.

 

[sheraz.pervaiz]

240 V mains has 50 Hz frequency(in other countries) and 120 V mains has 60 Hz frequency(in USA).

Since transformer's output frequency is same as input frequency, your problem might not be solved by using transformer.

 

[ender84567]

a switching supply can put out from dc to any frequency you want if built right, so that shouldnt matter as long as the RMS into it doesnt blow it up.

 

[alex.flory]

The current supply in Brunei is 50HZ but I think there is a range between 50 to 60Hz. So not sure about that. I have used devices from US before with a step down transformer and it worked well. Maybe just a minor issue. Thanks.

a switching supply can put out from dc to any frequency you want if built right, so that shouldnt matter as long as the RMS into it doesnt blow it up.

Hope that doesn't happen. Thanks.

Added after 1 minutes:

I think I pretty much made up my mind. Will definitely be getting the step down transformer but I may need to get the larger one at 4.5A max output and at 500w. I think that should be sufficient to power most devices. Thanks ya all.

 

[alex.flory]

Hi all,

Just an update. Finally went ahead and bought the 200W step down transformer. Tested my CNC controller and they all worked like a charm. Thanks to all who helped.

Alex