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Inductive Ballast

Author: Apogeeweb
Date: 4 Nov 2019


Ⅰ Overview

  1.1 Definition of Inductance Ballast

  1.2 Types of Inductance Ballast

  1.3 Environment to Use Inductive Ballast

Ⅱ Product Structure

  2.1 Working Principle of Magnetic Flux Leakage Ballast

  2.2 Construction, Shape and Production Process of the Inductance Ballast

  2.3 National Standards and Terminology of Inductance Ballast

Ⅲ Product Features

  3.1 Main Features and Advantages of the Inductance Ballast

  3.2 Comparison of Good Quality Ballasts with Common Magnetic Ballasts on the Market

Ⅳ Use and Installation of the Product

  4.1 Light Source Configuration of the Inductance Ballast

  4.2 The Normal Service Life and Warranty Period of the Inductance Ballast

  4.3 Precautions for Installation

Ⅴ Common Faults and Solutions for Inductance Ballasts

  5.1 Wire heating

  5.2 Trip

  5.3 Noise

  5.4 The Ends of the Lamp Tube Are Black

  5.5 Burnout


I. Overview

1.1 Definition of Inductance Ballast

A device that is connected between a power supply and one or more discharge lamps. Its main function is to limit the lamp current to the desired value by a combination of inductance, capacitance or inductance and capacitance. The device can be constructed from one or several separate components.

The ballast may also include components that function to vary the power supply voltage, provide an auxiliary startup voltage and preheat current, prevent cold start, reduce stroboscopic effects, correct power factor, and suppress RF interference.


1.2 Types of Inductance Ballast

(1) Impedance Ballast

It consists of an iron chip with a full air gap of the main magnetic circuit and a coil of a single winding. The principle of linear induced impedance limits the starting current and operating current of the matching lamp to a stable working range.

 Figure 1. Electrical Schematic of Impedance Ballast

Figure 1. Electrical Schematic of Impedance Ballast


The impedance inductance ballast is an impedance choke coil which is used in series with the HID light source. Its function is to limit it to a certain current under a certain voltage, so that the light source is in the starting current of the safe range when the light source is started. It is a constant current component when the light source is normally illuminated and kept in a certain working current.




a. The circuit is simple and easy to overhaul. It consists of compensation capacitor, electronic trigger and impedance ballast. The power factor of the circuit is ≥0.85.


b. The performance is reliable and stable. In the series circuit, the impedance ballast plays the role of a heart. The other compensation capacitors and electronic triggers are auxiliary working components. Since the ballast can work continuously for ten years in the coil temperature of 130 ℃ (by the TUV test in Germany), the ballast will not be damaged without damage to the light source.


c. With a wide range of applications, it can be used in high temperature environment, and will not be affected by the failure of the compensation capacitor. Its reliability is especially highlighted in integrated luminaires.


d. When the line works, the ballast itself has low power consumption so that it is also an energy-saving product.




a. The starting current is large, and the starting current is about 1.5 times of the working current. Due to the large starting current, the line capacity should be increased by 1.5 times during the line design, which is also a large cost.


b. When the light source is working, the lamp power is greatly affected by the increase of the power supply voltage. When the power supply voltage changes by 10%, the lamp power changes by more than ±30%, which will affect the life of the light source.


c. In the light source with high lamp tube voltage, the maximum service life of the light source cannot be fully satisfied. Because the tube voltage will self-extinguish when it exceeds 154V in the line voltage of 220V, and the lamp tube voltage will increase as the number of years the lamp is used increases. Of course, there are many factors that affect the life of the light source such as the quality of the lamp itself; the design parameters of the ballast and the compatibility of the light source. In short, the use of impedance is also a weakness to the maximum life guarantee of the light source.


d. Under abnormal conditions, after the two wires of the lamp are short-circuited, the current of the ballast is very large, and the heat is also very large, which may cause damage to the circuit if it last for a long time.


(2) Magnetic Flux Leakage Ballast


It is mainly composed of an iron chip with a shape air gap of the main magnetic circuit and a coil plus magnetic circuit piece of two windings. The primary winding obtains electric energy from the power grid, and the tap of the primary winding is connected with the secondary winding. By using the principle of electromagnetic induction, the electric energy is induced at the secondary winding and the starting capacitor end to meet the requirements for the starting voltage and stable working current of the matching lamp. The ballast's two characteristics of boosting and magnetic leakage have formed many characteristics different from those of the impedance ballast.

 Figure 2. Electrical Schematic of Magnetic Flux Leakage Ballast

Figure 2. Electrical Schematic of Magnetic Flux Leakage Ballast


The magnetic flux leakage ballast is an LC lead-type peak circuit. The fundamental wave is mutated by auto-coupling and local magnetic saturation, and then resonates with the working capacitor to obtain a higher open circuit voltage and a longer-lasting lamp operating current. It is a high-power factor lighting circuit with a line power factor of 0.90~0.97, which has its unique advantages for point HID light sources.




a. The starting current is small and it is less than the working current. We don't need to consider increasing the line capacity in the circuit design, which can reduce the large investment.


b. The voltage fluctuates but the lamp power is constant. When the voltage fluctuates by ±10%, the lamp power can be changed within 10%, which prolongs the life of the light source.


c. The higher open circuit voltage can prolong the life of the light source. The general open circuit voltage of the magnetic flux leakage ballast is above 300V (especially the metal halide lamp), which can provide an open circuit voltage higher than the impedance type. It greatly meets the requirement of open circuit voltage × 70% ≥ tube voltage.


d. The line power factor is relatively high, generally can be designed to between 0.9 and 0.97. it is a high power factor green lighting products.


e. Under the abnormal condition of the short circuit happened at two wires of the lamp, the incoming current is less, and the whole system will not be affected.




a. The volume is larger than the impedance type, and the cost is higher than the impedance type.


b. The output is connected in series with a capacitor to activate the lighting. The capacitor plays a very important role. If the capacity of the capacitor changes greatly, it will directly affect the lumen output of the bulb, but the capacitance is greatly limited by the temperature. Therefore, the requirements for the performance and temperature resistance of the capacitor are very high.


c. Because the temperature of the capacitor is limited, the environment is worse than the impedance ballast.


(3) According to the installation form


— Free-standing ballast: A ballast that can be installed separately from the luminaire without the need for an additional case. It can be a built-in ballast with a suitable case that provides the required protection marked on the logo.


— Built-in ballasts: Specially designed ballasts that can be mounted in luminaires, boxes or cases. The controller room in the base of the lamppost is considered to be a case.


— Integral ballast: A ballast that becomes an irreplaceable part of the luminaire and cannot be tested separately from the luminaire.


1.3 Environment to Use Inductive Ballast

Inductive ballasts cannot be used outdoors. If it must be used, it must be prepared for waterproof and moisture-proof, so as to avoid short circuit caused by water in the line; you should also pay attention to the ambient temperature, the general upper limit does not exceed 50 degrees, and the lower limit is not lower than minus 15 degrees, so as to avoid the inductance inside the lamp burn out due to excessive temperature or can't start and burn out due to the low temperature.


Ⅱ Product Structure

2.1 Working Principle of Magnetic Flux Leakage Ballast

When a 220V 50Hz AC power source is applied to the switch-closed circuit, current flows through the ballast, the lamp filament, and the starter to heat the filament (the starter is disconnected at the beginning, due to the application of an AC voltage greater than 180V, the arc of the gas in the starter is bubbled, and the bimetal in the bubble is thermally expanded and deformed, and the two electrodes are brought together to form a passage for heating the filament).


When the two electrodes of the actuator are brought together, the bimetal is cooled and the two electrodes are disconnected because there is no arc discharge. Since the inductance ballast is inductive, when the two electrodes are disconnected, the current in the circuit suddenly disappears, so the ballast generates a high pulse voltage, which is superimposed with the power supply voltage and then applied to the ends of the lamp to make the inert gas in the lamp tube ionize to cause arc discharge. (The high pulse voltage time is about 1ms 600V~1500V, and the exact voltage value depends on the type of lamp).


In the normal illumination process, the self-inductance of the ballast acts to stabilize the current in the circuit. An inductance ballast is a iron core inductor coil. The nature of the inductor is that when the current in the coil changes, it will cause a change of the magnetic flux in the coil, thereby generating an induced electromotive force whose direction is opposite to the direction of the current, thus hindering the change of the current, thereby limiting and stabilizing the current.


2.2 Construction, Shape and Production Process of the Inductance Ballast

(1) Construction

A. The magnetic ballast consists of a silicon lamination, an enameled coil, a skeleton end cover, a base plate (outer casing), and a terminal.

B. Role:


Coil: Generates an induced electromotive force. In the case of power-on, due to the existence of a certain resistance in the coil, power loss will occur, and the generated heat can increase the temperature of the inductance ballast and easily accelerate the aging of the ballast. In order to reduce the resistance in the coil, it is preferable to make a high-purity imported electrolytic copper enameled wire.


Silicon lamination: The whole conductor is in a changing magnetic field, which will cause an induced current inside the whole conductor, commonly known as "eddy current", which will cause the consumption of electric energy and the temperature rise. In the inductance ballast, the iron core is used to enhance the magnetic induction. However, due to the existence of the eddy current, it is necessary to use a thin iron core laminated with the insulated silicon lamination instead of the entire iron core to reduce the loss caused by the eddy current.


Base plate: plays a role in fixing and installing

Skeleton: plays a role in fixing the coil, chip and wiring

Terminal: plays a role in wiring and connects the inductance ballast in series to the circuit


(2) Shape:

At present, the more popular shapes are: West Germany type, European type, flat top type, Finnish type, Spanish type, etc.; chip structure can be divided into TU, TW, EI, etc.; size can be as determined as needed.


(3) Production process:

Winding → Test withstand voltage → Mounting base plate → Pressing, adjusting current, testing withstand voltage (automation) → Dipping insulating paint, drying, dip white paint, drying (automation) → Add terminal → Test withstand voltage, test current , testing the interturn voltage (automation) → Printing → Test power → Test withstand voltage → Packaging


2.3 National Standards and Terminology of Inductance Ballast

(1) National Standards of Inductance Ballast: GB19510.9-2005    GB/T14044-2005

 Figure 3.

Figure 3.

(2) The effect of properly reducing the current is:

① It can adapt to high voltage and unstable operation in some areas;

② It can reduce the temperature rise and help the ballast to extend its service life;

③ It can extend the life of the lamp.


(3) Terminology

① Line power factor, symbol: λ

The power factor of the combination of the ballast and the associated lamp


② High power factor ballast

Ballast with line power factor of at least 0.85


③ Rated maximum temperature of the ballast winding , symbol: tw

The rated maximum temperature of the winding is determined by the manufacturer. At this temperature, the life of the ballast is expected to be at least 10 years of continuous operation.


④ The rated temperature rise of the ballast winding, symbol: △t

The temperature rise of the winding is determined by the manufacturer under the conditions specified by the national standard.


Ⅲ Product Features

3.1 Main Features and Advantages of the Inductance Ballast

(1) Using high quality enameled wire, small resistance, low loss and low working temperature;

(2) Adopt high-quality silicon lamination, high magnetic flux and low loss;

(3) The performance is stable and it is designed according to the ten-year service life.


3.2 Comparison of Good Quality Ballasts with Common Magnetic Ballasts on the Market

—— 4~5 yuan 40W magnetic ballast on the market


① Poor appearance because it only dip white paint once, which is easy to rust and paint off;

② The terminals are thin and the color is too different;

③ The appearance logo is unclear and incomplete.


Performance requirements:

① The signed current is 430mA, which is only about 320mA, and the power is seriously insufficient;

② The temperature rise is high, generally above 80 ℃, and some even reach above 100 ℃. It is easy to burn out;

③ Power loss is greater than 11W, which consumes more power.


Materials and processes:

① The enameled wire is only 0.19~0.23mm, the wire diameter is small, the power consumption is large, and it is easy to burn out;

② The thickness of the base plate is 0.6~0.7mm, which is easy to have noise if the knot is not firm;

③ Plastic accessories are made of inferior recycled materials, which have poor high temperature resistance and are not flame retardant;

④ The chip adopts cold-rolled sheets with uneven thickness, which will cause large iron loss. It is processed by ordinary punching machine, which causes large burrs, poor precision, increased leakage magnetic loss and high noise;

⑤ There is only poor testing equipment, which is simple and not professional. As long as the lights are on, they are packed into the warehouse so the life is short.


—— Good quality inductance ballast


① Well appearance because it dip insulating paint once and also dip white paint once. It is double insulated and not easy to rust;

② Adopts flame retardant and high temperature resistant terminal with uniform color;

③ The appearance logo is clear and in line with the requirements of GB19510.9-2004.


Performance requirements:

① The signed current is 430mA and the measured current is 410mA~390mA, which meets the requirements of GB/T14044-94, and the power is sufficient;

② Low temperature rise, generally only 55 ℃, life expectancy can be more than ten years;

③ The power loss is only 5W so it can save energy.


Materials and processes:

① Using high-quality 0.29mm enameled wire with low power consumption and low temperature rise thus can save energy;

② The base plate is made of high-quality steel plate of 1.0~1.2mm, the knot is firm and the noise is small;

③ Plastic accessories are made of PAG, which has high temperature resistant and is flame retardant;

④ The chip adopts 0.2mm 470 high magnetic permeability silicon lamination with small iron loss and is punched by automatic high-speed punching machine. The precision of the silicon lamination is high, the burr is small, the magnetic leakage loss is reduced, and the noise is small;

⑤ The testing equipment is advanced, the semi-finished products and finished products are tested by the 2000V sound and light display withstand voltage test and electrical parameters test, and with the current advanced interturn short-circuit tester, each ballast is subjected to the interturn withstand voltage test before entering the warehouse in order to ensures that each ballast meets standards before leaving the factory.


Ⅳ Use and Installation of the Product

4.1 Light Source Configuration of the Inductance Ballast

The specification of inductance ballasts are generally the following (except for inductance ballasts for gas discharge lamps)

10W~65W: It can be adapted to fluorescent tubes and ring tubes with tube diameters from T6 to T12;

4W~14W: It can be adapted to the fluorescent tube with the diameter of T5;

Energy-saving lamp ballasts of 5W~11W, 13W, 18W, 26W: They can be adapted to the plug-in energy-saving lamps used in downlights.


4.2 The Normal Service Life and Warranty Period of the Inductance Ballast

Inductance ballasts are inspected strictly before leaving the factory. Each ballast is subjected to withstand voltage test, electrical parameter test, interturn voltage test, lighting test, etc. In the case of normal use, the life of each inductance ballast can be more than 10 years, and the warranty period is two years.


4.3 Precautions for Installation

① Power quality issues: It is required that the three-phase power supply should be balanced as much as possible, and the power supply voltage of each phase should not be too high, which is recommended to be 220V. In the early stage of installation of some projects (especially factories), due to the failure of the installation of the equipment, the voltage may be too high, which may exceed 270V. And the inductance ballast may have slight noise. The installer should pay attention to such problems.


② Installation quality issues: It is necessary to ask the installer to install the luminaire according to the installation diagram of the luminaire. If the luminaire and the ballast are not installed firmly, noise will occur. The luminaire and ballast should not be directly installed on the surface of the flammable items and in the places there are explosive gas, corrosive gas, liquid and dust. And it is not suitable for use in humid environments.


Ⅴ Common Faults and Solutions for Inductance Ballasts

5.1 Wire heating

The main reason why the wire is heated is that there are too much loads and the large current. The construction unit should design according to the value that nominal current of the lamp ballast multiplied by 1.6 times the instantaneous starting current. Some inexperienced construction units are designed solely according to surface power, ignoring the power factor of the inductor bracket is only about 0.5 and each ballast has about 8W of its own losses. (Power factor compensation is not energy saving, thus we need to improve the power quality of the power grid.


Power factor compensation is divided into two methods: single lamp/single machine compensation and centralized compensation. Single lamp compensation is a capacitor connected in parallel with each lamp. Centralized compensation generally sets up an automatic compensation screen in the power distribution room. According to the inductive load input into the grid, it can automatically input the power factor of the capacitance cosφ to keep close to 1 such as 40 sets of 40W*3 lamp panels.


Calculated from the surface alone, its current is 40W×3×10÷220V=5.45A

But actually it is (40W+8W)×3×10÷220V÷0.5=13.09A

Then plus the instantaneous starting current, it is 13.09A×1.6=20.9A

Solution: increase the compensation capacitor (cosφ - power factor)

 Figure 4.

Figure 4.


After adding 12μF compensation capacitor, the current is (40W+8W)×3×10÷220V÷0.9=7.27A

Then plus the instantaneous starting current, it is 7.27A×1.6=11.63A

That is: the line with no compensation capacitor can withstand current capacity of 20.9A or above, and the compensation capacitor is designed for 11.63A or above.


5.2 Trip

The reasons for the leakage switch trip are:

(1) The wire load is too much, and the current is too large thus cause a trip. In this case, the number of lamps is configured according to the leakage current.


a. Increase line power factor (plus compensation capacitor)

b. Decrease the number of lamps loaded by wires

c. Increase the value of the leakage switch (rated working current)


(2) If the ballast is broken or the lamp wire is damaged and in contact with the lamp case, it will cause leakage protection. In this case, it should be checked according to the actual situation. It is possible to detect the reason and replace the ballast or repair the damaged wire according to the actual situation.


5.3 Noise

Ballasts are designed to be silent, if there is noise in actual use:


(1) Check if the voltage is 220V. Because the new site has no other load, the voltage often is 240V~270V or higher. At this time, slight noise may occur, but it will disappear automatically when the voltage is normal.


(2) If the voltage is normal and there is noise, either the ballast itself has a problem, the leakage flux is large and is resonated with the lamp; or the lamp is not installed firmly, the density of use is high, the installation height is low, and the surface of the ballast is too close to the iron shell of the lamp.


(3) The national standard for noise is ≤ 35 decibels. In the case of no dispute, it is in compliance with the requirement that no obvious noise is heard within a distance of 1 m in the static chamber.


5.4 The Ends of the Lamp Tube Are Black

The reason why the ends of the lamp tube are black shortly after use may be:


(1) The quality of the lamp is poor, which is a common phenomenon of inferior lamps that often appear on the market, and some of them may not be activated or started for a long time;


(2) The ballast starting current is too small, and the starting impact time is too long;


(3) The ballast starting current is too large, and the impact on the filament is large, which makes it easy to blacken the lamp and burn out the lamp tube. Inductance ballasts are produced according to the standard. If the two ends of the lamp are black shortly after use, there should be a problem with the quality of the lamp and that has nothing to do with the ballast.


5.5 Burnout

The occurrence of burnout of the ballast is caused by a short circuit between interturn of the coil or a short circuit caused by a high temperature rise. It is mainly due to:


(1) Enameled wire has a lot of pinholes (the national standard stipulates that there are 25 pinholes per meter or less). If the pinhole of the enameled wire and the pinhole of the interturn are in the same place, an inter-turn short circuit will occur when the voltage is too high;


(2) If the voltage is too high or used for a long time under abnormal conditions, since the voltage used by the inductance ballast is extremely strict, for every 10V increase, the operating current will increase by about 35mA; when the voltage is increased by 20V, the operating current will increase by 70mA. If The operating current is 400mA at 220V, and the operating current is 470mA at 240V. In this case, there is generally no burnout, but in an abnormal situation (ie, a short circuit occurs in the starter), the lamp is in the startup state for a long time.


There will be a rise in temperature that will lead to burnout. (So if we find that the lamp does not light for a long time or the starter is in the closed state for a long time, we should immediately check whether the lamp has burned out or the starter has been short-circuited. It should be replaced immediately, otherwise it will cause the high temperature rise of the ballast and accelerate its aging, which seriously affects its life and even cause burnout.)




1. What is inductive ballast?

The inductive ballast is just a big inductor wound on a laminated iron core. It has two functions: it limits the current and generates the high voltage to strike the lamp. Fluorescent tubes have a negative resistance characteristic and therefore cannot be directly connected to the mains.


2. What is the advantage of electronic ballast compared to inductive ballast?

Electronic ballasts are more efficient than magnetic ballasts in converting input power to the proper lamp power, and their operating of fluorescent lamps at higher frequencies reduces end losses, resulting in an overall lamp-ballast system efficacy increase of 15% to 20%.


3. Is a ballast an inductive load?

A familiar and widely used example is the inductive ballast used in fluorescent lamps to limit the current through the tube, which would otherwise rise to a destructive level due to the negative differential resistance of the tube's voltage-current characteristic. Ballasts vary greatly in complexity.


4. Can you bypass a ballast on a fluorescent light?

If the existing fluorescent tube fixture you want to replace has a non-shunted tombstone, you can proceed with the ballast bypass procedure. Nonetheless, if the existing fixture offers a shunted tombstone, you should replace it with a non-shunted variant.


5. What is the difference between a transformer and a ballast?

A transformer changes the amperage and/or voltage. It literally ‘Transforms’ electrical energy. A ballast is like a capacitor. ... The electrical ballast stores energy in the same way that a water ballast stores water for stability.


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