400watt HPS powering it

I hope this help you to understand how a High Pressure Sodium Light Works.​

A grow light is a an electric lamp that's light has been specifically designed to have all of the qualities of natural sunlight that are necessary for healthy plant growth.
These are used by indoor gardeners to simulate a natural outdoor environment and help plants and flowers grow to their full potential.​

The HPS grow light is well known for being energy efficient, and it has a long lifespan providing illumination, which makes it popular with professional indoor greenhouses and gardeners.​

These lights will normally, with proper care, last approximately two years, while producing nearly six times as much illumination as ordinary grow lights.
Another benefit of HPS lighting is it's use of sodium gas, producing a flower boosting red spectrum of light.​

The HPS grow light is meant to be primarily used during the reproductive stage of the vegetation's lifespan, though it can be used in combination with metal halide lighting.
Ballasts are required when using the HPS, they ensure that the power level remains constant and the light works smoothly, without any explosions.​

The fixture also needs to be kept a safe distance from the plants to prevent the heat from burning their fragile leaves, stems, and flowers.​

For areas with space constraints, using an air cooled bulb system can overcome the need for distance from fragile greenery.​

When gardening indoors, the HPS grow light is one of the best options for growing marijuana or any other plants supplied with natural nutrient providing radiance.
　
　
　
How Does a High Pressure Sodium Work?
　
　
Light
A sodium vapor lamp is a lamp that uses sodium to create light.
It can come in a high pressure or low pressure format.
High pressure lamps have more components than low pressure and contain other substances such as mercury.
The lamp produces a clarity of light that creates vivid color from objects illuminated by it.
The tube of a high pressure sodium light is generally made out of aluminium oxide, due to its resistance to the high pressure, and xenon, that is used as a starter for the light because it won't react with the other gases.
Voltage runs to the light through a ballast, which regulates the current.
　
　
Ballast
The arc of gas that extends from one end of the tube to the other is created when ignited, and is made up of metallic sodium and mercury vapor.
The temperature of the vapor is controlled by the power supplied to the lamp.
With higher power comes higher temperatures and thus higher pressure in the tube, which creates more light.
The ballast is an inductive ballast that helps regulate this power by keeping the current constant, instead of the voltage.
　
　
Operation
The inductive ballast is made up of a coiled wire.
The coil creates a magnetic field inside when a current is applied.
It stores the energy of the current in the magnetic field it creates.
This way it controls the output current that continues on to the light.
The store of energy also helps in the starting of the light when it is off, by sending an extra volt of electricity when the current first starts into the coil.​