What size step down transformer do I need?

Asked By: Mariuxi Rustarazo | Last Updated: 26th May, 2020
Category: science physics
4.6/5 (1,574 Views . 24 Votes)
You will need a step-down voltage transformer if you're traveling to any country with a power standard that is higher than what your appliances use. Conversely, taking appliances that run on 220–110 volts to the U.S. or Canada requires a step-up voltage converter that can transform 110–120 volts up to 220–240 volts.

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Then, how do you size a step down transformer?

A 120-volt motor has a load amperage of 5 amps. Multiply 120 volts times 5 amps this equals 600VA now lets multiply the 125 percent start factor. Take 600 times 1.25 this equals 720VA and most transformers are sized by a factor of 25VA or 50VA. The required transformer would be a 750VA or .

One may also ask, how many watt transformer do I need? Example: If your appliance consumes 80 Watts then you need a AC-100 transformer (100 Watts capacity) or higher. If you want to operate 2 appliances on one transformer. One of them consumes 300 Watts and the other 130 Watts then you would need a AC-500 (500 Watts capacity) or higher.

Besides, how big a transformer do I need?

Once your landscape lighting design is complete, you can figure out what size of low-voltage transformer you need. Transformers generally range from 150- to 900-watt capacity. For example, if you plan to use 20 12-watt lights, multiply 12 times 20 for the total wattage. In this example, the total wattage is 240.

How do I choose a transformer?

Before Selecting a dry-type Transformer

  1. Determine is it three phase or single phase.
  2. Determine power line voltage and frequency it will be primary voltage for your transformer.
  3. Determine voltage for your application it will be secondary voltage of the transformer.
  4. To determine the capacity required in volt-amperes.

36 Related Question Answers Found

How do I know what size cable I need for my transformer?

Transformer full load current is calculated by:
  1. Ifull-load = 12.5 × 106 / 1.73 × 20 × 103 = 361 A.
  2. Therefore subsequent current rating of cable to be 361 / 0.97 × 0.84 = 443 A.
  3. Isc = K × A / √t.
  4. Isc = 240 × 143 / √1 = 34.4 kA.
  5. Vd = Ifl × XL × sinφ + Ifl × R × cosφ volts.
  6. If = (1000 × 0.15) / (1 + 0.15) = 131 A.

Why are transformers rated in KVA?

The transformer does not alter the power factor of its output power. Transformers are rated in kVA because the losses occurring in the transformers are independent of power factor. KVA is the unit of apparent power.

How do you determine if a transformer is step up or step down?

If the primary voltage is higher than the secondary, then the transformer is acting as a step-down transformer; if the secondary voltage is higher than the primary, then the transformer is acting as a step-up transformer.

How can I make a step up transformer at home?

Building an Electrical Step-up Transformer
  1. Use a large steel bolt as the transformer's magnetic core.
  2. Wrap the bolt with insulating tape to isolate the windings from the “core”.
  3. Wind the two copper wires several times (at least 12 turns) around the ends of the “core” (steel bolt).

How do you convert VA to amps?


3 phase VA to amps calculation formula
  1. I(A) = S(VA) / (√3 × VL-L(V) ) So amps are equal to volt-amps divided by the square root of 3 times volts.
  2. amps = VA / (√3 × volts) or.
  3. A = VA / (√3 × V) Example.
  4. I = 3000VA / (√3 × 110V) = 15.746A. How to convert amps to VA ?

How many KVA is 200 amps?

Generator KVA Rating to Amperage Conversion Chart 80% POWER FACTOR
kV•A kW 480V
250 200 301
312 250 376
375 300 451

What size transformer do I need for a 200 amp service?

For example, the apparent power for a 200 A at 240/120 V single-phase service is 48 kVA. The utility will not typically install a 50 kVA transformer. The standard sizes of single phase transformers are 5, 10, 15, 25, 37.5, 50, 75, 100, and so on.

How does a step up transformer work?

A transformer converts alternating current (AC) from one voltage to another voltage. It has no moving parts and works on a magnetic induction principle; it can be designed to "step-up" or "step-down" voltage. So a step up transformer increases the voltage and a step down transformer decreases the voltage.

How do I know what size LED transformer I need?

To work out how much LED tape you can run off an LED power supply, simply divide the wattage of your LED strip driver (for example, 100w) by the wattage per metre of your LED tape (e.g. 4.8w p/m). This gives you the total length of LED tape, in metres, that your LED power supply can drive.

What transformer do I need for LED lights?


All LED bulbs require a 'driver' (a special type of transformer) to work properly. Mains voltage LEDs (such as GU10 and B22 bulbs) have the driver built in to the bulb. MR16 and other 12V bulbs use an external driver.

How many lights can I run off a transformer?

If you want to connect ten landscape lights to a magnetic transformer, and the lights use 30 watts each, you would need a 375 watt transformer. (10 lights X 30 watts = 300 watts, and 300 is 80% of 375).

Can I plug a 220v into 110v?

If you plug a 220V device into 110V outlet, it will normally last a little longer before it dies. But: An AC mechanical drive may fail to start, or it may take up more current than it is designed for, and eventually burn out. The insulation is usually not a problem unless there is a major flaw in the design.

What is the difference between a transformer and a converter?

The difference between the two lies in how the device actually converts the voltage current. To reduce 220V to 110V, for example, a converter chops the “sine waves” (the shape of the AC power bursts) in half, whereas a transformer alters the length of the sine waves.

How do you size a generator?

Make a list of the items that need to be powered by the generator. Make a note of the starting and running wattage of the respective items. Calculate the total power requirements in KVA or KW.

Can I convert 110v to 240v?

Check the details of the power-supply of the device on whether it supports only 110V or is stating as input "100V - 240V". If it does, check whether it has a switch to change it from 110V to 240V. If it has no switch, all you need is a socket adaptor.

Can I convert 120v to 240v?

Yes you can convert a dedicated 120V 20A receptacle to a 240V, 20A receptacle (by connecting the white neutral to the other phase and using a 2 pole 20A breaker), but using a NEMA 14-50 as the receptacle is not a good idea.