Questions tagged [autotransformer]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
0
votes
2answers
79 views

Power supply with output of 24V, 500mA

I am currently trying to design a power supply (non-isolated) with input of 440V AC and output of 24V/500mA. Can I use an autotransformer for this? I know I can use conventional transformer, but I ...
4
votes
2answers
539 views

Using 3-tap 127/220V to 12V transformer as a poor man's 127V to 220V autotransformer

I need to actuate a few contactor switches that need 220VAC in its coils. The problem is, my application is fed by 127VAC. Therefore, I need something like a 10W, 127V to 220V autotransformer. These ...
0
votes
0answers
33 views

the amount magnetic induction kVA?

the question and solution is given below: How did he know that 10 kVA is transformed by magnetic induction? SOURCE: Electrical Machines, Drives, and Power Systems by Theodore Wildi. Sixth edition, ...
6
votes
3answers
578 views

What's the right replacement for vintage "glass cloth insulation" that transfers heat in Variac?

I ripped apart a broken 1950s-era Variac autotransformer to diagnose an internal short in the core, and found a layer of gooey insulating fabric mat between the coil/taps and the mounting plate: The ...
3
votes
2answers
316 views

Old Variac -- chassis ground? is it safe?

I've got an old (vintage!) GenRad Variac (below) that has two prong plug and two prong socket. I want to modify it to add a safety earth pin to both input and output. In doing so, I opened it up and ...
0
votes
1answer
72 views

HF/HV - rectification or modulation?

Lets put it simply: The aim is to rectify the high frequency/high voltage (i.e. 200 kHz, 100 kV) output to 12-24-48 V DC. or Modulate (possible amplitude modulation?) the HF/HV output with 50 Hz. ...
6
votes
2answers
979 views

How does the component "alarm boost three pin inductor" make a piezo buzzer louder?

I have a small circuit working on 2xAA batteries (3V) with an MCU and a buzzer for alarm sound. I've already successfully used an active buzzer (with build-in driver oscillator) drived by an NPN ...
0
votes
0answers
39 views

Variac and Other dropper in line

I have a beautiful old variac, with a sliding (rotating) center contact. I would love to use this on a nice LED string inside a glass bulb on top of the device. But also, use the variac as the dimmer, ...
0
votes
1answer
39 views

Reading audio transformer datasheet

I'm using an audio transformer SP-70 to isolate audio. (http://catalog.triadmagnetics.com/Asset/SP-70.pdf) The question arises what is the maximum AC current allowed to operate the transformer without ...
1
vote
1answer
185 views

Connecting a 120V/30A variac to a 240V circuit

I have a variac rated for a maximum output of 30A. The problem is it takes 120V on the input and all of my 120V circuits are 15A, as expected. I unfortunately cannot just add an additional 30A circuit ...
2
votes
0answers
38 views

Reduce switching noise on autotransformer

I am trying to achieve the same thing they are talking about in this post, which is controling an autotransformer via software. I accidently even got the exact same autotransformer, but instead of a ...
0
votes
0answers
152 views

calculation of total capacity of Bank of 3 single phase transformer?

Imgur This is a nameplate of single phase auto-transformer. However in this transformer i'm not sure how do I get the capacity of this transformer. 3 of these transformers are connected in to form ...
0
votes
1answer
302 views

Autotransformer vs Inductive Divider

Which is the advantage of using an autotransformer instead of a simple inductive divider?
0
votes
1answer
504 views

Can a Variac be modified to output higher voltages?

Since variable transformers can be had quite cheaply these days (under AUD 45 / USD 30 / EUR 27 today for a 500 watt one through eBay from China) they are cheap enough to experiment with. I bought ...
0
votes
2answers
228 views

Software controlled variable voltage AC supply with SSR relays

I have an autotransformer like this one : I would like to control it with an arduino solid state relay like this one: What would happens if I wire every output of the transformer together to the ...
0
votes
1answer
163 views

What will happen when taps at secondary side of auto-transformer are connected together (short-circuited)?

In case of Auto-transformer, there is only one winding, having three lead wires (1 for primary/input, 1 for secondary/output, and 1 common between both). At the secondary side (the output side), there ...
0
votes
1answer
52 views

vario trafo 4 terminals, trouble shooting

So I got a bare vario trafo and with 4 terminals, 2 terminals are constantly showing around 3 ohms (primary maybe?) the to other 2 terminals can vary in ohm as I turn the wheel (secondary?). So I ...
2
votes
1answer
1k views

Tapped vs. Coupled Inductor

I have reverse engineered a sounder circuit which appears to be using a center tapped inductor. Since then, I have tried to find center tapped / 3-pin inductors and cannot find them from a reliable ...
0
votes
1answer
1k views

Step up SMPS with unrealistic voltage output with a 100W LED COB load

I got some 100W LEDs to make a lamp, realized with a boost converter I could use an old ATX power supply and bingo I'd be fine. It worked at first, until I didn't like the color so I decided to ...
1
vote
1answer
2k views

Two windings transformer to autotransformer

Let's say that we have a transformer with two windings (source: circuitstoday.com) with nominal power \$S\$, nominal voltages \$V_1\$ and \$V_2\$ and windings \$N_1\$ and \$N_2\$ respectively. The ...
1
vote
1answer
5k views

Winding EI core Stepup transformer for inverter

I want to learn the method or concept for winding Inverter Transformer(12V to 220V), How to select Core size Wire gauge Bobin Size Turn Ratio and/or number of turns for different VA ratings on EI ...
0
votes
2answers
1k views

Auto-Transformer: how to understand the following diagram?

I have a question about the CW Auto-Transfomer that I will be using. The wiring diagram is above. As you can see, the equitment takes 277/240/208/120V as input. But on its specification sheets, it ...
0
votes
1answer
352 views

Why does the current in autotransformer motor starting gets reduced squared in relative to the voltage?

Say, relatively, the motor's full voltage rating's voltage, current and torque are 100, 100 and 100 Why does when the autotransformer tap is set at 80%, the motor runs at 80 64 64 65% and 50% as ...