Measure the frequency of a transformer / High Voltage / Forums

Forums

4hv.org :: Forums :: High Voltage

« Previous topic | Next topic »

Measure the frequency of a transformer

1 2 next

Move Thread

LAN_403

mihlikos

Sun Nov 13 2011, 05:13PM

Registered Member #3947 Joined: Mon Jun 13 2011, 11:06PM
Location:
Posts: 16

I need to measure the output frequency of a hv transformer.The transformer have no label or any specs.
Which way you would do this?

Michael

Mattski

Sun Nov 13 2011, 06:14PM

Registered Member #1792 Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527

The output frequency is the same as the frequency you drive it with. If it is made with laminated iron rather than ferrite, then it's probably designed for 50Hz or 60Hz standard AC supplies. One way to see if you're driving it at the correct frequency is to measure the input current, which could be done by inserting a small series resistance and measuring the voltage across it with an oscilloscope (with an isolated probe mind you, not a grounded one). If using a sinusoidal source (e.g. the wall outlet) then the current should be fairly sinusoidal, if it spikes up at the peaks of the sine wave then the core is saturated and it needs to be driven at a higher frequency.

klugesmith

Sun Nov 13 2011, 07:46PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

I think he means a "transformer" with mains power plug on one side, and high voltage on the other. I think these usually work in the low ultrasonic frequency range, not at hundreds of kHz. Michael, can you point us to an Internet picture of a transformer that looks about like yours? Can you (or younger people) hear a high-pitched tone when it's on?

As for the laboratory approach, start by listing instruments you already have to measure frequency. Oscilloscope or frequency counter? Computer or mobile device with a microphone, noting that it will have a low-pass input filter at less than half its sample rate? Musical instruments tuner?

Coupling the high voltage to the input of an electronic counting instrument is probably as simple as running an open-ended wire sort of close to the high voltage, until the counter runs.

You could use a CMOS counter IC such as CD4040

to divide any likely transformer frequency down to an audible frequency or even blinking-light frequency (see link). It would help to bias the clock input at a voltage near its logic threshold, using megohm resistor[s].

mihlikos

Sun Nov 13 2011, 08:54PM

Registered Member #3947 Joined: Mon Jun 13 2011, 11:06PM
Location:
Posts: 16

Thank you for the reply s,

I have an oscilloscope,signal gen and some multimeters.No freq counter but can find a microphone and a computer. This is the transformer.

The input is 50V to 230V with a variac and in series a variable capacitor.

My goal here is to reach 500 khz on the output.But for first step i need to know how to measure it.

Inducktion

Sun Nov 13 2011, 09:37PM

Registered Member #3637 Joined: Fri Jan 21 2011, 11:07PM
Location: Buffalo, NY
Posts: 1068

Uh. That looks like a laminated iron transformer.

What exactly are you trying to accomplish? It will output the same frequency as the input. Since you're using a variac, I'd assume the output to be either 50 hz or 60 hz. Transformers don't change output frequency.

You will NOT be able to push 500 khz AC into that. It will saturate beyond all belief, and a ferrite based transformer will work much better.

mihlikos

Sun Nov 13 2011, 11:52PM

Registered Member #3947 Joined: Mon Jun 13 2011, 11:06PM
Location:
Posts: 16

@Inducktion
iam trying to build a power supply 200kv 500khz for a project.

With a dimmer to the input i can get from the transformer 180-200kv but dont know the hz.
Not sure if the insulation will handle this voltage for long time.I need ideas on how to measure the hertz so i can decide if i need to proceed with building new coil/transformer set up to raise the hz accordingly.

Herr Zapp

Mon Nov 14 2011, 03:46AM

Registered Member #480 Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644

mihlikos -

You keep repeating the same question about "measuring the output frequency", but it seems you are not understanding the responses you are receiving.

Once again: the frequency of the AC output of an IRON CORE transformer will be the same (repeat: THE SAME) as the frequency of the AC input you are driving it with.

This appears to be a conventional tape-wound iron-core transformer, designed for 50 or 60Hz service. If it is a special transformer for avionics use (unlikely), it may be designed for 400Hz service.

500KHz (that's what you said, right? 500,000Hz?) is completely out of the question.

Herr Zapp

Steve Conner

Mon Nov 14 2011, 08:14AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Well, unless you were to use it to drive a Tesla coil designed to resonate at 500kHz.

mihlikos

Mon Nov 14 2011, 09:56AM

Registered Member #3947 Joined: Mon Jun 13 2011, 11:06PM
Location:
Posts: 16

Herr Zapp

Ok i understand that,Thanks

So,due to magnetic saturation cannot have what i need.So there are two options?One is to build a transformer with a ferrite core or an air core.

To my question if i understand right, one way to measure the hz output from a supply is to connect it to an inductive load and place a simple air coil near it that is connected to a frequency counter.

Can you point me to some plans for building a transformer for 200kv 500khz ?

Michael

Mattski

Mon Nov 14 2011, 04:55PM

Registered Member #1792 Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527

Actually it is due to high frequency loss mechanisms that you cannot do 500kHz with an iron core, the power losses would just be too high. Magnetic saturation happens when the frequency is too low.

The technique that you describe to measure the output frequency could work, I assume that you'd do it that way to avoid applying high voltage directly to the frequency counter.

200kV is quite large for a transformer, and you also need to specify output waveform: sinusoidal AC, DC low ripple, DC high ripple, or something else. This will inform the design you choose, but if you're okay with AC then a Tesla Coil could suit your purposes.

1 2 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob