Transformer Question

Started by Anonymous in sci.electronics.design8 months ago 91 replies

I was looking at the commercial isolation transformers and they are very costly, so I decided to build my own. After all, all they are is...

I was looking at the commercial isolation transformers and they are very costly, so I decided to build my own. After all, all they are is a transformer with a power cord on the primary and an outlet (and fuse) on the secondary. And I already have an enclosure to put it in. I'm looking at a bare transformer to use as an 120v isolation Transformer. (120v in, 120v out). The transformer primar...


Little 1:10 audio transformer as HV transformer

Started by Jan Panteltje in sci.electronics.design6 years ago 125 replies

Little 1:10 audio transformer as HV transformer Thse are small transformers with a ferrite core, specified as 6H secundair, and turns ratio...

Little 1:10 audio transformer as HV transformer Thse are small transformers with a ferrite core, specified as 6H secundair, and turns ratio 1:10. (conrad nr 516260). The idea was to make 400 V from 5 V with a PIC. That requires at least 40V peak primary. I tried some BC547B, but changed to a IRLZ434N MOSFET, as this one has the reverse diode for free, I tried many frequencies and pulse w...


calculating saturation current of transformer

Started by Anonymous in sci.electronics.design9 years ago 7 replies

I have designed a 1:1 transformer that will be used in a low voltage DC:DC converter. I have tested the current at which the...

I have designed a 1:1 transformer that will be used in a low voltage DC:DC converter. I have tested the current at which the transformer saturates by decreasing the frequency of the primary voltage while keeping the secondary open loop. I would like to calculate the theoretical value of the current at which the transformer will saturate. I tried using the formula in Flanagan's which relate...


Variations in PA Transformer response

Started by Martin Stall in sci.electronics.design7 years ago 12 replies

Can anyone help me figure this out? I have two standard PA 100V output line matching transformers, of different size from different suppliers....

Can anyone help me figure this out? I have two standard PA 100V output line matching transformers, of different size from different suppliers. Each has an 8 ohm primary. Transformer #1 is rated at 5W Transformer #2 is rated at 60W, and is obviously larger in size. Transformer #2 has much lower internal resistance on both windings, and a lower turns ratio. How can this produce the same ...


Current transformer with good coupling?

Started by Klaus Kragelund in sci.electronics.design6 years ago 15 replies

Hi I am working on a design in which we need to have very good coupling from primary to secondary of a transformer. The transformer is used...

Hi I am working on a design in which we need to have very good coupling from primary to secondary of a transformer. The transformer is used as a current transformer and we must have very high accuracy from primary to secondary, so we have the same current on the output also. We are using a toroid xformer with bifilar windings (4 wires in parallel to yield a transformer with 4 windings...


Toroidal Audio Transformer

Started by hamilton in sci.electronics.design6 years ago 3 replies

I am looking at replacing an audio transformer. The size I have now is larger than my case. I need to have a smaller transformer and thought...

I am looking at replacing an audio transformer. The size I have now is larger than my case. I need to have a smaller transformer and thought a toroid type might work. Has anyone worked with this type of audio transformer ? Are there any web sites for calculating the size / power output ? I would like 10-15 watts output. Thank you hamilton


transformer ET specs

Started by Jamie Morken in sci.electronics.design10 years ago 1 reply

Hi, For this gate drive transformer: http://www.coilcraft.com/da2099.cfm It has a Volt-time spec of 221 V-us) So the primary will...

Hi, For this gate drive transformer: http://www.coilcraft.com/da2099.cfm It has a Volt-time spec of 221 V-us) So the primary will saturate in 1us at 221 volts, or 20us at 11 volts I think. This transformer is specced to work for gate driving from 20kHz to 250kHz, and it has a 1:1 turn ratio. So for a fet gate voltage of 11V, this transformer could pulse for a maximum of 20us? ...


RF transformer

Started by Robert Baer in sci.electronics.design4 years ago 40 replies

I understand, that with the proper winding configuration, that a 90 degree phase shift can be achieved between primary and resonant...

I understand, that with the proper winding configuration, that a 90 degree phase shift can be achieved between primary and resonant secondary. That is done with a tapped secondary on a FM discriminator transformer. What are the guidelines and requirements needed to construct such a transformer at a given frequency OTHER than the standard 10.7Mhz? Say, on a form in the one inch d...


HF step up transformer

Started by Jamie Morken in sci.electronics.design9 years ago 13 replies

Hi, For a step up transformer with an input voltage of 60VDC to 125VDC, and a fixed output voltage of 420VDC, at 350watts, what is the most...

Hi, For a step up transformer with an input voltage of 60VDC to 125VDC, and a fixed output voltage of 420VDC, at 350watts, what is the most efficient transformer type to use? I would like to use a flyback but I don't know if I can get to 92%+ efficiency with this. cheers, Jamie


Current transformer

Started by Tim Williams in sci.electronics.design6 years ago 114 replies

Would've been nice if I had known a current transformer isn't a very good transformer. Instead of two terminals, it acts more like a single...

Would've been nice if I had known a current transformer isn't a very good transformer. Instead of two terminals, it acts more like a single terminal, with your poor burden resistor caught in the middle. Ah well, such is basic research... Tim -- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms


Toroidal Transformer Screening

Started by Syd Rumpo in sci.electronics.design2 years ago 11 replies

Hi Another magnetics question! I have a SMPS which uses a toroidal ferrite transformer. It switches at ~100kHz, works very well, it's not...

Hi Another magnetics question! I have a SMPS which uses a toroidal ferrite transformer. It switches at ~100kHz, works very well, it's not my design and I can't change it. However, it introduces noise at about 50kHz onto/into my electronics which causes a problem. After much experimentation, I found that putting an earthed screen around the transformer kills the problem quite dra...


HELP to make LEDs work with AC current

Started by Mark Main in sci.electronics.design9 years ago 13 replies

I have a transformer that is reducing the AC supply voltage down to 25.5VAC, which connects to a thermostat that connects to a Honeywell water...

I have a transformer that is reducing the AC supply voltage down to 25.5VAC, which connects to a thermostat that connects to a Honeywell water valve for my home boiler system, which then completes the circuit back to the transformer. I don't see an amperage limit marked on the transformer--it's about baseball size, so it's not small. Only 1 of the poles of the relay is used and I would like...


Any technical reason not to use isolation transformer to make DC?

Started by Mike Silva in sci.electronics.design9 years ago 59 replies

If I want a source of 150-160VDC is there any technical reason why I shouldn't use an isolation transformer to feed a rectifier & filter? As...

If I want a source of 150-160VDC is there any technical reason why I shouldn't use an isolation transformer to feed a rectifier & filter? As opposed to a purpose-designed 120VAC secondary "power transformer"? Mike


FCC phone line and transformer

Started by Anonymous in sci.electronics.design9 years ago 3 replies

I have a few modems laying around and noticed, (especially on the lower cost ones), that there isn't even a transformer on the PCB...

I have a few modems laying around and noticed, (especially on the lower cost ones), that there isn't even a transformer on the PCB for interfacing to telphone line. All of them are using DAA chips but I would assume that a transformer would almost be mandatory in getting part 68? approval. Guess not though? I have one modem here, a motorola, that just goes straight into the phone line...


Re: calculating saturation current of transformer

Started by Phil Allison in sci.electronics.design9 years ago 2 replies

> I have designed a 1:1 transformer that will be used in a low voltage > > > DC:DC converter. I have tested the current at which the...

> I have designed a 1:1 transformer that will be used in a low voltage > > > DC:DC converter. I have tested the current at which the transformer > > > saturates by decreasing the frequency of the primary voltage while > > > keeping the secondary open loop. > > > > ** How is that finding a "current" ?? > > > > What you have likely found is a combination


Current transformer

Started by Sylvia Else in sci.electronics.design2 years ago 42 replies

I was looking for a cheap clip-on current transformer to use to monitor my power usage, and I found...

I was looking for a cheap clip-on current transformer to use to monitor my power usage, and I found this: http://efergy.com/au/products/accessories/microjackplug-extra-sensor#.VmZZQF42GVI which I guessed (correctly) was a current transformer. I that have no intention of using it with Efergy's products, since they don't seem concerned about the voltage, which can vary somewhat from n...


R-core mains transformer problem

Started by N_Cook in sci.electronics.design8 years ago 13 replies

300W transformer that over 4 years of use, the secondary voltages are 10 percent lower than originally, at least. Measuring without full...

300W transformer that over 4 years of use, the secondary voltages are 10 percent lower than originally, at least. Measuring without full rated loading, so worse than that under load presumably. If the transformer was severely jarred, via its mounting bolts, could that open up the core closure and consequential drop in efficiency or some other R-core type generic reason for drop? will it get w...


Build your own Over Unity Motor

Started by The Flavored Coffee Guy in sci.electronics.design9 years ago 82 replies

Just remember this, a transformer is designed for a purpose and it can be either a step up transformer or a step down transformer. Everything...

Just remember this, a transformer is designed for a purpose and it can be either a step up transformer or a step down transformer. Everything else you need to know is here. Go to this web site to pick up the basic theory: http://elgersmad.homestead.com/files/resonance/transformer_motor_theory.pdf Go to this link to understand that it will work: http://www.gutenberg.org/files/11498/1149...


Using SSR to switch transformer

Started by Arlet Ottens in sci.electronics.design9 years ago 39 replies

Hello, I'm considering using an SSR to switch the primary side of a transformer. The transformer is a toroid, 230V -> 27V. The secondary...

Hello, I'm considering using an SSR to switch the primary side of a transformer. The transformer is a toroid, 230V -> 27V. The secondary side is fixed to a 1 Ohm nichrome wire heating element. I've read some articles that say switching on at zero crossings causes a high inrush current, and that it's best to switch on at peak voltage. If I follow this advice, are there any other issu


0.2MHz - 2MHz step up transformer

Started by Paul Jackson in sci.electronics.design6 years ago 80 replies

I am looking for an impedance matching transformer that will convert the 50 Ohm output of my function generator and to a 1K Ohm...

I am looking for an impedance matching transformer that will convert the 50 Ohm output of my function generator and to a 1K Ohm resistive load. That provides a 20x step-up as well, so with losses 10V yields maybe 100V. Frequency range is anywhere between 200KHz to 2MHz. Required current, up to 20mA. I would definitely prefer a ready-made transformer. Does anyone know under what app...