In the previous post about how ozone is made we covered the basics of a corona discharge ozone generator. In that post we pointed out that there are three main parts to a corona discharge ozone generator:
- Power Supply – this edition
- Corona Cell
Ozone Generator Power Supplies
In this article we will cover the differences in power supplies used for corona discharge ozone generators. Also, the different parts that are involved in the power supply itself. While some are very simple, other may be very complicated. First, we have to cover the basics of what these power supplies do.
Corona discharge ozone generators operate on the principle of a high voltage spark across a dielectric to form a corona. The main component to any corona discharge power supply is a transformer to increase voltage from the standard 120 or 220 VAC power used to a higher voltage ranging from 500 – 20,000 volts. This high voltage will create the spark (corona) necessary for ozone generation.
The voltage used by an ozone generator is mainly dependent upon the dielectric and air gap in the corona cell. If there is a larger gap for the spark/corona to jump, a higher voltage is needed. Also, thicker and various types of dielectrics will require varying voltages. We will cover dielectric and corona cell design in future installments of How Ozone is Made.
Another factor is frequency. Higher frequency ozone generators (see below for info in frequency conversions) will typically use lower voltages as this is less stress on the frequency conversion components and smaller gap ozone generators are more conducive to higher frequencies.
Line frequency ozone generators may use a basic rheostat to adjust the voltage into the transformer. This will in turn, adjust the output voltage of the transformer and adjust the rate of ozone production. In these ozone generators only a transformer and rheostat are used, no other electrical devices are necessary for ozone production.
Some transformers may use a line choke, or a series of transformers to achieve a the voltage step-up necessary. This is an example of a larger (~450 gram/hour) ozone generator transformer assembly.
Many ozone generators used what is basically a car coil to increase voltage in an ozone generator. When ozone generator design was still new there were very few choices for transformers that could endure the abuse of 1,000 Hz, elevated voltage, and changing variables inside a corona cell. Today, transformer options are greater and the use of a basic car coil is becoming less common.
Most high frequency transformers are much smaller, open coil type transformers. This image is very typical for what may be used inside a higher frequency ozone generators. This same style transformer is used in some medium frequency ozone generators.
The spark inside an ozone generator is generated from high voltages created by the transformer, these voltages are all AC (alternating current). This means the electrical current alternates direction. This reversal of electrical current occurs at a constant speed we call frequency. This is measured with Hz (hertz). Here in the USA typical electrical power is delivered at 120 VAC 60 Hz. This means the voltage is 120 volts of alternating current, that alternates 60 times per second. In other countries power may be delivered at 220 VAC 50 Hz.
This explanation is all to understand that the spark or corona inside the ozone generator with no frequency conversion would occur 50 or 60 times every second. Many of the earlier ozone generators, and some still today operate at line frequency, an unaltered frequency. This is generally referred to as a line frequency ozone generator.
Other ozone generators use a higher frequency to increase ozone output. Higher frequencies would create more spark/corona every second. There are three main types of ozone generators:
- Line Frequency – 50-60Hz
- Medium Frequency – 100 – 2,000 Hz
- High Frequency – 5,000 – 30,000 Hz
This circuit board is the driver board for a car coil type transformer as seen in the image above. This is a great example of how simple the circuitry may be in a typical medium frequency ozone generator.
This is the power supply for a larger (up to 450 gram/hour) high frequency ozone generator. This power supply can supply an output of up to 30,000 Hz, or as low as 1,000 Hz. As you can see this power supply is much more circuitry and components are used to achieve these higher frequencies and flexibility.
This power supply is for a larger (up to 400 gram/hour) medium frequency ozone generator.
Putting it all together
There are many different types of ozone generator power supplies for many different applications. Each serves a unique purpose in the ozone generation world. Each has advantages and disadvantages.
Line Frequency Ozone Generators (50-60 Hz)
Line frequency ozone generators commonly use larger transformers and voltages from 10,000 – 20,000 volts. The only other electrical component for operation is a rheostat as pictures above. These are very simple and reliable setups that perform well for many years. Absolutely nothing beats the reliability of a line frequency ozone generator.
As the components on most line frequency ozone generators are larger to achieve the same ozone output the costs for the transformer and rheostat are higher than the costs for the smaller transformers and simple printed circuit boards used for medium frequency ozone generators. Also, line frequency ozone generators cannot achieve near the performance as the higher frequency ozone generators.
Medium Frequency Ozone Generators (100 – 2,000 Hz)
Medium frequency ozone generators are most common today. These ozone generators may produce 1 gram/hour to thousands of pounds/day of ozone. The image above is a simple printed circuit board to increase line frequency to about 1,000 Hz, this board is attached right to the transformer that increase voltage to about 1000 volts. This is an older design with a oil filled automotive style coil. however this is a good example of the typical size of power supply for a 5 – 20 gram/hour ozone generator. There may be multiple power supplies powering multiple corona cells in one ozone generator to produce more ozone. This is a very compact, cost effective, and efficient method to produce ozone.
While medium frequency ozone generators are fairly simple there are still more components than a line frequency ozone generator. This means there are more things to fail and cause problems. Due to the elevated frequency these generators also produce more heat, both in the electronics and corona cell. Heat is the enemy of ozone.
Medium frequency ozone generators are also louder than others. While this may not be a large concern in every application, at some frequencies there is a high pitched whine that is not acceptable in some occupied spaces.
High Frequency Ozone Generators (5,000 – 30,000 Hz)
High frequency ozone generators offer very compact designs due to smaller transformers and corona cells. As the spark/corona is occurring up to 30,000 times per second the need for a large air gap and high voltage are alleviated. In return the electronic circuit board becomes the largest, and most expensive component of some high frequency ozone generators. This is illustrated very well in the above image. This shows 3 power supply circuit boards with the small transformer mounted right to the circuit board!
High frequency ozone generators may be very energy efficient and compact in size allowing for a very flexible platform to either use multiple cells for redundancy or other configuration changes. Many high frequency ozone generators are very cost effective as the large parts that carry a higher price (transformer and corona cell) are smaller, while the circuit board and electronics are more elaborate.
High frequency ozone generators contain many components that may fail. They also produce a great deal of heat due to the high frequency. However, with the very high frequency there is no audible sound from the ozone generators, they are the most silent of all types. Many manufacturers have just begun implementing more high frequency components in the last 5 years. Expect big changes in the future in this area of ozone generation.
This covers the basics of ozone generator power supplies. I promise the following editions of How Ozone is Made will be shorter and less technical.
The next edition of How Ozone Is Made will cover Corona Cell design in Corona Discharge Ozone Generators.
If you have any questions about ozone generators, or what may be best for you, call our application engineers today! We are glad to answer questions, dispel myths, and be a general information source for your ozone related questions.