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On the Airbus A320 ECAM electrical page there are two TR or transformer rectifier and they convert AC or alternating current electrical power into DC or direct current electrical power. But on the ECAM it shows that TR has Volts and Amps but what are they? Are they the new DC current coming out of the TR or the AC current entering the TR? On the subject of Electrics, what even is AC/DC BATBUS and what is there purpose?

Screenshot of A320 ELEC display

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  • $\begingroup$ No under the TR is V/A but does the TR have their own voltage and amps or is it the DC V/A leaving the TR or the AC V/A entering the TR? $\endgroup$ – Itzyoboi Oct 3 '17 at 22:17
  • $\begingroup$ @mins Power will remain the same, but it is not shown. Amperage will increase with decreasing voltage. $\endgroup$ – user9394 Oct 6 '17 at 1:12
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What is displayed would be the OUTPUT of the TR. Those values tell you that (if) the TR is working, and how hard it is working. If it's supposed to be putting out 12 volts but the actual output is something significantly different, then the TR isn't working correctly. The amps value tells you how much DC current is being demanded of the TR -- maybe something on the associated bus is consuming too much current (and is thus perhaps the source of smoke that you're trying to eliminate), or another TR in parallel has failed. The failed TR would show 0 volts & 0 amps, while the operative TR would show normal volts & higher than normal amps.

If you want to know the voltage of the input to the TR, you'd select the generator or bus that is powering the TR to see that. Voltage is typically a value of a bus, while amps is generally the value of a source, such as a generator, battery, or TR. The source is putting out however many amps. While you can measure the voltage of a bus coming directly off of an electrical source (so we talk about a generator's or battery's or TR's voltage), you can also measure (and will frequently care more about) the voltage of a bus, independent of what source is powering it right now. If my Essential DC bus has normal voltage, then the important things on it can be expected to continue operating, regardless of whether the current source for that bus is the #1 TR or the #2 + #3 TR's in parallel or the battery charger or the main battery or the standby battery or whatever else that particular aircraft may have.

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The TR voltage is the voltage being supplied by the TR. The amperage shown is the demand on the TR.

A bus, be it AC or DC, is a source of power distribution. Typically, a generator will provide power to an AC bus. That AC bus then provides power to a large host of devices which require (typically) 115 VAC. Usually there is redundancy such that if one generator fails, another generator can pick up the bus.

A DC bus usually uses a T-R to convert 115VAC to 28VDC and then distributes that 28VDC power to whatever devices require the use of DC. The same type of redundancies as the AC bus can be assumed.

Aircraft batteries are also another source of 28VDC power. Usually that power is directly fed from the batteries to whatever devices require it. These are often named "Battery Direct Bus," "Hot Battery Bus," etc... They often power emergency systems like engine fire bottle squibs, emergency lights, etc...

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