Seecol manager Mr. James Mathews explained how an induction lamp works and told the below things.
How an Induction Lamps Works:
Induction Lamps create light by using an electromagnetic field to excite mercury particles mixed in an inert gas like argon or krypton. The mercury creates a UV light and a phosphor on the inside of the bulb or tube filters the energy into visible light. This is a type of fluorescent light. Unlike a standard fluorescent light, induction lamps do not use electrodes in the tube.
The induction lamps have three parts: frequency generator (ballast), discharge tube and electromagnet (aka: inductor, energy coupling coils or energizing coils).
First the ballast creates high frequency current (230 or 250 KHz).
The current is sent through the electromagnet and an electric field is produced. The number of turns (times the wire is wrapped around the iron core) is determined by how each product is designed (so it is not consistent among different lamps).
Energy is transferred from the magnet to the mercury in the tube in the same way that a transformer works... induction.
The mercury vapor emits UV light which strikes the phosphor and makes light.
NOTE: The HEP induction lamps work differently;
The ballast is made of four parts. First is an EMI filter to reduce harmonics from the supply of alternating current. The next part is a bridge rectifier; this converts AC to DC power. After that is the PFC circuit which boosts the DC voltage to a constant 400 V value and increases the power factor to 0.95+. The final part of the ballast is an inverter which converts the DC power to high frequency AC. For a more advanced discussion of the ballast and control read here.
Type of Induction Lamps
There are three kinds of induction lamps: external, internal and HEP
External Induction Lamp - this uses an induction coil mounted outside of the bulb or tube. The metal coil which is covered by a sheath is clearly visible. A soft or rubberized material is used to prevent the metal ring from coming in direct contact with the glass tube.
High frequency energy is sent from the ballast to the electromagnet. This creates a powerful magnetic field, this excites the mercury amalgam in the protruding small tub (see diagram below). It is normal for mercury when it cools from a vapor form to escape to the coolest part of a bulb or tube; this is usually on the ends of a standard fluorescent tube or HID discharge tube. The small tube is designed to consistently capture the mercury after the lamp is turned off. The tube is located close to the inductor so that the powerful magnetic field easily excites the mercury. The mercury vaporizes and spreads throughout the rest of the tube. It continues to be excited since the magnetic field reaches more than 6 inches in the examples below. If the lamp is large enough two inductors are needed to keep the entire tube area excited. Just as in a standard fluorescent lamp, the mercury vapor creates UV and this is converted into visible light via the phosphor.
Internal Induction Lamp - this works on the same principle as the external induction lamp except that the electromagnet is placed inside of the glass bulb. This is typically used when you need a small lamp in a normal household socket.
High Efficiency Plasma (HEP) - A new type of induction lamp has been developed called the high efficiency plasma or HEP. The HEP lamp performs at 90 lumens per system watt.
The HEP lamp is a "Plasma Lamp" just like the LEP. The LEP was developed earlier in 2001, it uses a dielectric waveguide made of ceramic. Much of the light was lost in the ceramic waveguide resulting in loss of efficiency. Ceravision changed the design using a clear quartz waveguide which improved the lamp and forms what we call the HEP.
Sulfur Lamp - The sulfur lamp is also a plasma lamp. It uses microwave radiation to excite sulfur vapor mixed with argon to create light. 2.45 GHz radiation hits an electrode less bulb that contains a sulfur powder. You can identify the lamp by a metal screen on the outside of the lamp. The bulb operates at a very high temperature and most models need a fan for cooling.