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I'm trying to wire an autotransformer for usage as a speed controller for a brushless motor fan.

The terminals are quite self explanatory:

Pe for ground, L-N are my input, N1-L1 are unregulated output (same as L-N) and U-N are the output to my motor. Having that said, I'm still hesitant to wire this up before I understand the the following:

  • Q1: What is the U terminal? What does it stand for?
  • Q2: Do I connect my motor's ground to the common Pe? I'd have imagined that there would be a dedicated terminal for the ground near the output to the motor.

Here's a picture from inside the transformer's case:

Transformer's datasheet https://www.sentera.eu/Product/ViewDocument/ENG/?DocumentId=690814&ArticleID=108450

Adi
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1 Answers1

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Sentera's website shows a connection diagram for a similar controller:

enter image description here

Figure 1. Source: Sentera.

Pe for ground, L-N are my input, N1-L are unregulated output (same as L-N) and U-N are the output to my motor.

N1-L should read N-L1. Yes, unregulated output but on when running so it is switched.

Q1: What is the U terminal? What does it stand for?

'U' is commonly used in Europe to mean 'voltage'. It makes sense when you think that we use 'I' for current and avoids confusion between 'voltage' and 'volts'. U1 and U2 are the fan terminals and the naming suggests that neither of them is at neutral potential so the triac is likely to be in the neutral line.

Q2: Do I connect my motor's ground to the common Pe? I'd have imagined that there would be a dedicated terminal for the ground near the output to the motor

Yes. It appears that they have been a bit mean with the terminals.

Transistor
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  • Aha, so U is just to indicate "variable voltage be here". I didn't think to look at the wiring diagram because it's for triac-based speed controller and not a transformer. Thank you for the information. – Adi Jul 20 '17 at 18:35
  • Ground has nothing to do with meanness. In these kinds of installations ground is not supposed to be looped through devices, but rather is to be taken from a dedicated and reliable wire or bus-bar. – Asmyldof Jul 20 '17 at 19:05