# Electrical Engineering: Transformer Question for Power Shower

• Sawyer888
In summary, the current at the secondary of the transformer is ~10 times the current in the primary. This means that any resistance on the secondary gets transformed or multiplied by that factor squared to the primary. This can cause a voltage drop and hence current drop on the primary.
Sawyer888
Hi, I'm an apprentice multiskilled engineer, thought I prefer electrical engineering

anywho, my power shower at home stopped working and upon testing there was no ouput from the transformer, 230v/24v DC and it got me thinking, I'm aware of the step up/down voltage theory etc and the windings etc.

If the the voltage is stepped down roughly ten times doesn't that in theory mean the current is stepped up ten times, but surely this can't be the case for a little electric motor in a power shower would be blown to bits if the current was ramped that high

Could someone explain to me what's happening here?

cheers

Last edited:
The current at the secondary of the transformer is ~10 times the current in the primary. This means that any resistance on the secondary gets transformed or multiplied by that factor squared to the primary.

So if your motor has a resistance of 24 ohms and draws one amp, that load will be transformed to ~2400 ohms at the primary. The current into the primary will be only about 0.1 amp.

The amount of current used is determined by the voltage divided by the resistance. Having a high current available doesn't mean it will all be used by the load.

skeptic2 said:
The current at the secondary of the transformer is ~10 times the current in the primary. This means that any resistance on the secondary gets transformed or multiplied by that factor squared to the primary.

So if your motor has a resistance of 24 ohms and draws one amp, that load will be transformed to ~2400 ohms at the primary. The current into the primary will be only about 0.1 amp.

The amount of current used is determined by the voltage divided by the resistance. Having a high current available doesn't mean it will all be used by the load.

So are you saying that whatever the load/resistance is on the secondary coil (24v motor) and its properties directly affect the resistance on the primary coil and therefore causes a volt drop and hence current drop on the primary because whatever resistance the motor has is proportionally stepped up onto the primary side.

That has confused me a bit because I didn't think the secondary coil and its loads etc could effect the primary side, I assumed the primary side was static and it's properties didn't change on the basis of the secondary side

Sawyer888 said:
So are you saying that whatever the load/resistance is on the secondary coil (24v motor) and its properties directly affect the resistance on the primary coil and therefore causes a volt drop and hence current drop on the primary because whatever resistance the motor has is proportionally stepped up onto the primary side.

Yes, within the limits of the transformer. If you put a short on the secondary of a transformer, the primary will also appear as a short. With an open on the secondary the primary will appear as the inductance of the primary.

The voltage drop is the voltage across the terminals of the device. Since the primary of a transformer is across 230 VAC that is its voltage drop. The load on the secondary won't affect that. It will affect how much current is flowing in the primary however.

You can picture the primary as a high inductance coil with a resistor in parallel. The value of the resistance is the value of the resistance on the secondary times the turns ratio squared. When the secondary is open the resistor in parallel with the primary is also open. As you load the secondary with less and less resistance, the resistance across the primary also drops allowing more current to flow. In reality there is no resistor across the primary. All of the primary current flows through the coil. This is just how it behaves.

Cheers I think I have a better understanding of this now

nice1 laa

## 1. What is a transformer and how does it work?

A transformer is an electrical device that is used to change the voltage level of an alternating current (AC) electrical circuit. It works by using two coils of wire, known as the primary and secondary coils, that are wrapped around an iron core. When an alternating current flows through the primary coil, it creates a magnetic field which induces a voltage in the secondary coil, resulting in a change in voltage level.

## 2. How is a transformer used in a power shower?

In a power shower, a transformer is used to step down the electrical voltage from the mains supply to a lower voltage, typically 12 volts. This lower voltage is then used to power the electric shower pump, which increases the water pressure for a more powerful shower experience.

## 3. What factors should be considered when selecting a transformer for a power shower?

Some important factors to consider when selecting a transformer for a power shower include the input and output voltage levels, the power rating of the transformer, and the type of transformer (e.g. step-down or step-up). It is also important to ensure that the transformer is compatible with the specific make and model of the power shower.

## 4. Can a transformer be used to increase the water pressure in a power shower?

No, a transformer cannot be used to increase the water pressure in a power shower. The primary purpose of a transformer in a power shower is to step down the electrical voltage, not to increase water pressure. To increase water pressure, a pump or other type of pressure-boosting device would need to be installed.

## 5. Are there any safety considerations when using a transformer for a power shower?

Yes, safety is an important consideration when using a transformer for a power shower. It is important to ensure that the transformer is installed and wired correctly, following the manufacturer's instructions. The transformer should also be regularly checked and maintained to prevent any potential electrical hazards.

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