switching transformer problem

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bc327
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switching transformer problem




by bc327 » 09/07/07, 19:53

Hello,

Contrary to what my nickname would suggest, I am completely nil in electricity ...

I just registered on this forum because I have a problem to turn on 2 12V halogen spots 300W for swimming pool with 2 300 VA switching transformer.

I know that my electrical installation is good, as well as my spots because when I use a toroidal transformer 12V 300 VA, I know turn on my spots successively.

The characteristics of my new 2 transformer are here: http://www.prozic.com/dmx/info.php?ref=TRHALO300VA

My spots do not light up : Evil:

When I test the output voltage, it only indicates 3.2 V :?:

If I only plug one cable from my tester, I have 16 V :?:

By cons, my transformer provided with a spot gives me a correct tension when I plug my tester.

I tested the 2 transfo which react in the same way. Are they both defective, or are they not suitable for my pool spots?
Last edited by bc327 the 09 / 07 / 07, 21: 05, 1 edited once.
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bc327
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by bc327 » 09/07/07, 19:55

I read that switching power supplies required minimal power to operate.
This may explain why my tester only indicates a voltage of 3.2 V. So I connected 1 spot of 20 W and 2 spot of 20W to the 12V output of my transformer. I then get respective voltages of 6.46 and 8.78 V.

Nevertheless, none of the 2 switching transformer works to turn on my pool spot (300W) placed at about ten meters (6 square section cable) while the toroidal transformer works perfectly : Evil: My connections are not in question :?:
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Obelix
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by Obelix » 09/07/07, 20:58

Hello,

I just think they are not powerful enough to power a halogen lamp from 300 Watts.
At the start the consumption of these lamps triggers the security in current.
Do a test with the spot AND an incandescent lamp in series (100W mini), the spot should start!

Obelix
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elephant
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by elephant » 09/07/07, 21:02

1) beware of digital voltmeters: as their input impedance is very high, the measurement is false empty because there is no load on the source you measure

2) some switching processors pass the weapon to the left when applied to them with insufficient or no load. Maybe it's already too late.

3) for obvious safety reasons, it is necessary to use transformers (copper only) called "with 2 separate safety windings" to supply the swimming pool spots. These transformers are specially approved for this kind of use
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bc327
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by bc327 » 09/07/07, 21:09

Thank you for your advice Elephant. But that does not explain why these transformers do not work to turn on my spot of 300 W, because at the beginning I made my connection then it is only after that I tested because it did not enlighten.

For Obelix, it is an 12V transformer of 300 VA. It is therefore in theory quite powerful for a 12V 300W lamp.
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Other
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by Other » 09/07/07, 21:14

Hello

Just measuring on an output does not give much indication
These transforms work in high frequency and the volteterre can not read the values
more 300VA for a lamp of 300watts it is rather tangant
cold the lamps ask a current pick that this transformer is not able to issued, the 300watt is hot lamp on.
These internal protoson protoson when you ask them etrop dourouring it crashes to not burn
a cold lamp requires double instantaneous power
a traditional transformer and able to take a good instant load even a short circuit.
These transformers should be placed closest to the otherwise big-spinning lamps for the 12 volts which drops quickly to 10volts at the end of the queues
try with a small lamps 25 watts that will light
If you want to really measure the output rectifies the output with a diode bridge you will measure in DC
It would have been better to have a standard transfot like in battery chargers.

Andre
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bc327
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by bc327 » 09/07/07, 21:21

However, the toroidal transformer also makes 12V 300 VA and works perfectly. In addition, I placed 6 square section cable.

If still the lighting worked at a slightly lower intensity. But here it is nada :?:

Well, I think I'm going to send back these useless processes. I will leave for the shipping costs.
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by Other » 09/07/07, 22:21

Hello

A toroidal transformer is an autotransfo it's illegal for immersed pool lamps ..

It's not for nothing that lamps work in 12 volts it takes a primary and secondary transformer isolated
It's like many lamps in the bathroom and the razor socket. The thread must be No 12 we speak of 25 ampere by lights
especially quartz lamps they perform, if the voltage is sufficient.

lose 1 volt in the line under 12 volts it's a lot
lose 5 volts under 220volts it's negligible


Andre
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by crispus » 09/07/07, 22:25

Hello

Andre wrote:These transforms work in high frequency and the voltmetre can not read the values
...
a cold lamp requires double the instantaneous power


For having made the manipulation to my students with a lamp 24V-60W and a transformer, the resistance is almost 10 times lower cold (~ 20 ° C) lamp lit (~ 2300 ° C).

If the circuit allows it (low impedance), the ignition current can reach 10 times the rated current. But in practice it's rare because we dimension the cables to the fair.

The "total" temperature rise time read on the oscillator is of the order of 0,1s (with a delay due to the saturation of the transformer).

This measurement to 1 € 50 makes it possible to verify that the resistivity of the tungsten has a temperature coefficient of approximately 0,004.
Image
In passing by extending the curve R = f (T) in the negative, we also realize that we will have R = 0 for a temperature called "absolute zero" (~ -273 ° C).

Like what the pioneers of physics did not need sophisticated hardware or billions of dollars to impress us : Cheesy: : Cheesy:
And there is still a lot of things to discover in the back of the garage ... Is not it André? : Mrgreen:

To come back to the subject, the switching transformers are provided with circuits for safety against overloads or idling. In principle they are suitable for a single type of associated lamp.

And as André points out, the switching frequency is higher than that which the Meter can not cash.

Students "burned" several multimeters while testing this kind of power supply, because the displayed voltage being almost zero, the device automatically switches to the lower caliber. When the "mV" caliber is reached, the measuring chip breaks down since the real voltage is several volts.
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by elephant » 09/07/07, 22:39

Yeah!

In summary: buy a special transformer pool (a good old iron-copper) at a wholesaler of electrical equipment

connected with 6 wire or 10 mm² of section, the shortest possible and places a fuse in the secondary (there also request advice at the wholesaler)

That said: we are not very econologie.com, guys :D
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