How to check the choke of a fluorescent light bulb
Not long ago, the fluorescent light bulb was the only alternative to the incandescent bulb. It helped to save energy, and to a certain extent, to choose the color temperature of the light. But one problem not every home handyman could cope with - troubleshooting and fixing them in the additional elements that accompany daylight bulbs.
Table of basic faults
The main types of faults that occur in practice in the chokes are summarized in the table.
| Type of failure | What does it lead to | External manifestation |
|---|---|---|
| Breakage of coil winding or internal wiring | Circuit breakage | Lamp does not light (not even flashing) |
| Intertwist fault | Loss of inductance, decrease of reactance | Burnout of lamp coils (including after replacement), flashing without stable ignition |
| Ground fault | In a circuit with a protective conductor, creates a ground fault | If a PE conductor is connected, causes overcurrent and triggers a protective device If there is no protective earth in the mains, it may not manifest itself, but the mains voltage is still present on the device housing |
| Loss of ferromagnetic properties of the coil core (as a result of overheating, etc.) | Loss of inductance, reduction of reactance | Burnout of lamp coils (including recombustion after replacement), flashing without stable ignition |
Ways of checking
To diagnose the condition it is desirable to use instruments, but if they are not available, the condition can be evaluated without them.
Without a tester
Check choke of a fluorescent lamp can be checked without a tester or other tools (at least a screwdriver). But the reliability of these methods is limited.
- First and foremost is the behavior of the lamp. If it flashes when energized, but does not reach a steady glow, then there is reason to check the choke (although there may be other causes, including a malfunction of the lamp itself). If there is a break in the coil, there will be no flashing - the circuit will show no signs of life at all.
- Visual Inspection. If the throttle body is blackened, swollen, traces of local overheating - all this is a reason to doubt the serviceability of the device. It must be replaced or diagnosed with the help of devices.
- Installation in known faulty luminaire instead of regular one.. If after replacement the luminaire stops working, it means that the problem is in the choke. Or, on the contrary, you can install a known good choke in a non-working luminaire. If the problem is solved, then the fault is found.
You can assemble a stand to check control gear elements. It makes sense if you have to maintain lighting system of the building, officeThe reason for this is to maintain lighting system of the building, office, workshop, etc., built with fluorescent lamps. As a test bench, you can take a ready-made lamp and replace the standard parts in it with test parts, or you can build a simple circuit. It uses an ordinary incandescent lamp for 220 volts.
The inductive resistance properties of the choke coil are used to check the choke of the daylight lamp. Different situations are possible:
- the lamp is on at half light - the choke is intact, its reactance limits the current in the series circuit;
- lamp lights up at full brightness - there is inter-turn short circuit, inductance of the coil is small, reactive component of resistance is close to zero
- lamp does not light - Interrupter breakage inside the choke.
Check elements of electronic ballast (ELECTRONIC BALLASTS) on such a test bench is not possible. It works on a different principle.
If a choke with a body breakdown is tested, the line voltage will be present on its body when power is applied. Connect the elements of the control gear must be switched off. Take precautions when power is applied.
Using a multimeter
The multimeter gives more possibilities to check the control gear elements and the reliability of such testing is higher.
Open circuit
To check for breakage, connect a multimeter in resistance measurement mode (or audio diode) to the ballast pins. If the device is good, the tester will show a resistance of a few tens ohms (depends on the type of choke, most common models have about 55...60 ohms).
If the circuit is open inside, the meter will show infinite resistance.
The ballast can also be checked for breakage with an indicator screwdriver. This can be done without removing the unit from the luminaire, just by removing the cover and applying 220 volts power (by turning on the light switch).
It is necessary to check the presence of voltage at the input of the choke and then at the output. If power comes to the input of the ballast, but there is no power at the output, it means that there is a break in the choke.
Read also: How to wire a fluorescent lamp correctly
Short circuit
A short circuit is not a common fault. It can occur as a result of a global problem - sintering of coil turns, etc.
This is the same as the open circuit test, but in the case of a fault the digital meter will show a resistance of about zero.
A much more likely problem is an inter-turn fault. It is almost impossible to detect in the resistance test mode. If a small number of turns are shorted (2-3), the ohmic resistance will not change much, and the inductance will drop dramatically. Not every inexpensive multimeter has a function for measuring inductance with sufficient accuracy. Besides, it is necessary to know the inductance of a working device, and this parameter is rarely specified by the manufacturers. However, you can try to compare the inductance of the ballast under test with the inductance of a known working ballast.
Also a change in the core parameters (due to overheating, mechanical damage, etc.) can lead to a loss of inductance. And in this case, the fault is not easy to detect.
To check for frame breakdown
To check for ground breakdown, you need to connect one probe of the tester to the body of the device, the other to the lead of the ballast (then to the other).
If the choke is intact, the multimeter will show infinite resistance. If a breakdown is present, either zero or some value depending on the location of the breakdown:
- if the breakdown occurred at point 2, the tester will show total resistance of the coil;
- if at point 1, zero;
- at point 3 - some intermediate value.
Regardless of the location of the breakdown, the measured resistance will be less than infinity.
Conclusion
Traditional ballasts of fluorescent lamps are replaced by electronic (EBs), and the fluorescent lamps themselves are actively becoming a thing of the past - it's time of total domination of LED lighting. But in the past daylight lamps were popular, they were equipped with a large number of lighting systems, they are still produced today. Therefore, the question of checking the chokes for malfunction will be relevant for a long time to come.
