Transformer drawing 1 amp

Started by Anonymous in sci.electronics.basics16 years ago 36 replies

I have a transformer that is drawing about 1 amp when the secondary is not in use. Is this normal? Its a 15amp 12V CT transformer. ...

I have a transformer that is drawing about 1 amp when the secondary is not in use. Is this normal? Its a 15amp 12V CT transformer. The secondaries read 12 volts from the center like it should(its actually about 13V). It had what I guess what a thermistor(a rectangular box that as stuck inside the transformers windings) but I took it out because I thought it might be the problem. It hums...


300 ohm to 75 ohm impedance matching "transformer"

Started by Joe in sci.electronics.basics15 years ago 3 replies

I bought a 300 to 75 ohm "matching transformer" to hook up to a home built TV antenna. The matching transformer looks exactly like the one on...

I bought a 300 to 75 ohm "matching transformer" to hook up to a home built TV antenna. The matching transformer looks exactly like the one on this URL: http://www.solidsignal.com/prod_display.asp?PROD=WMXFMRPT I have a couple of questions: Can these matching transformers be used in either direction? That is, my antenna will get the 300 ohm end, and the TV antenna input will get the ...


What is a unbalanced AC transformer?

Started by Uriah in sci.electronics.basics13 years ago 4 replies

I need to provide a 10VAC power supply to a cirris cable tester and they said it was unbalanced. It is a three pin input with the center being...

I need to provide a 10VAC power supply to a cirris cable tester and they said it was unbalanced. It is a three pin input with the center being neutral and each side is hot 10VAC but it is unbalanced. What do they mean by unbalanced? How would I wire that up? And is there a way to tell how to wire it in from looking at the device, I don't have the that power supply. Thanks Russ


transformer winding ratio question

Started by panfilero in sci.electronics.basics11 years ago 3 replies

I have a basic question about transformer ratios, if I have 3 windings, a pri, a sec and an aux, what's the voltage expression for each winding?...

I have a basic question about transformer ratios, if I have 3 windings, a pri, a sec and an aux, what's the voltage expression for each winding? My guess is Vpri = Npri/Nsec Vsec = Nsec/Npri Vaux = Naux/Npri is this right? thanx!


smps: AC or pulsed DC fed into transformer?

Started by Anonymous in sci.electronics.basics7 years ago 26 replies

It seems to me that flyback SMPSes use pulsed DC instead of AC. Is this true? For example, here, the transistor simply turns on and off,...

It seems to me that flyback SMPSes use pulsed DC instead of AC. Is this true? For example, here, the transistor simply turns on and off, providing pulses to the transformer, right? http://www.repairfaq.org/sam/smpsbd.gif Would SMPSes be more efficient if their transformers were fed high-frequency AC instead of high-frequency pulsed DC (for example, by using an H-bridge to provide a neg...


Isolation transformer?

Started by Bob Engelhardt in sci.electronics.basics3 years ago 19 replies

I was looking for a 120-120 isolation transformer on eBay and I kept finding 120-240/480 transformers. There are 2 secondaries on these...

I was looking for a 120-120 isolation transformer on eBay and I kept finding 120-240/480 transformers. There are 2 secondaries on these (connect in parallel or series). It occurred to me that I could use one of these as a 120-120 by using one secondary as input and the other secondary as output. I know that this is theoretically possible, but are there practical reasons why it wouldn'...


Misusing a transformer

Started by david eather in sci.electronics.basics3 years ago 6 replies

Just a sanity check if you don't mind. I have a 230v to 30v 1amp 50Hz transformer - is there anything wrong with plugging that into 115v 60Hz...

Just a sanity check if you don't mind. I have a 230v to 30v 1amp 50Hz transformer - is there anything wrong with plugging that into 115v 60Hz to get 15v 1 amp out?


results of AC buck tranny

Started by default in sci.electronics.basics2 years ago 8 replies

I wired a 24VAC transformer to my Air Conditioner to lower the incoming line voltage to 220 from ~250 VAC. The old AC was pulling 2100+ watts...

I wired a 24VAC transformer to my Air Conditioner to lower the incoming line voltage to 220 from ~250 VAC. The old AC was pulling 2100+ watts worst-case and went to 1700, with the added transformer. Other observations: It uses ~1500 in the mornings when the differential between inside and out is close (all readings with the compressor running). During the day when the power was up ...


transformer core material

Started by Tom Del Rosso in sci.electronics.basics1 year ago 29 replies

AIUI you use iron cores for low frequency and ferrite for high frequency because ferrite doesn't get magnetized, so why couldn't aluminum do the...

AIUI you use iron cores for low frequency and ferrite for high frequency because ferrite doesn't get magnetized, so why couldn't aluminum do the same? -- Defund the Thought Police


DC motor supply

Started by Bob Engelhardt in sci.electronics.basics1 year ago 5 replies

I have a 24v DC motor that I'm using with a PWM controller supplied by a 24v SMPS. I want to be able to briefly switch the motor to 48v with a...

I have a 24v DC motor that I'm using with a PWM controller supplied by a 24v SMPS. I want to be able to briefly switch the motor to 48v with a relay. I don't have a 48v supply, but I do have a 24v transformer & bridge. I know that the following will give me the 48v, and I think that the Motor Control will be OK with it. But I'd like to know if I'm missing something. The relay will d...


MOV Search

Started by ABLE1 in sci.electronics.basics1 year ago 4 replies

Hello, I am an Alarm Technician among other things or stuff. I was thinking about installing a simple MOV on the Transformer that feeds...

Hello, I am an Alarm Technician among other things or stuff. I was thinking about installing a simple MOV on the Transformer that feeds power to the Alarm Board. The industry standard is 16.5VAC 40VA plug in Transformer. 120 Volt Input. Can anyone point to a specific MOV that would serve as a good lightning or surge protection if placed across the output terminals of the transformer...


Transformerless power supply

Started by amdx in sci.electronics.basics2 years ago 7 replies

Is it reasonable/possible to build an 8 amp 20 V transformerless power supply from a 120Vac line. I calculate about 180uf plus or minus...

Is it reasonable/possible to build an 8 amp 20 V transformerless power supply from a 120Vac line. I calculate about 180uf plus or minus depending on other components. Maybe 9- 20uf caps in parallel? I'd like to build it into a leaf blower. All plastic, absolutely no metal exposed. I think I've answered my question, I have 12, X rated caps in my junk box, but they are only 1uf....


Transformerless Power Supply

Started by amdx in sci.electronics.basics4 years ago 10 replies

Is it reasonable/possible to build an 8 amp 20 V transformerless power supply from a 120Vac line. I calculate about 180uf plus or minus...

Is it reasonable/possible to build an 8 amp 20 V transformerless power supply from a 120Vac line. I calculate about 180uf plus or minus depending on other components. Maybe 9- 20uf caps in parallel? I'd like to build it into a leaf blower. All plastic, absolutely no metal exposed. I think I've answered my question, I have 12, X rated caps in my junk box, but they are only...


how to reduce the mains voltage

Started by default in sci.electronics.basics2 years ago 26 replies

I have an older window air conditioner that I'd like to hang on to for a few more years. The name plate says it is 220 VAC and since the power...

I have an older window air conditioner that I'd like to hang on to for a few more years. The name plate says it is 220 VAC and since the power company went through and upgraded the distribution network and replaced HT and transformers my service which had been running 210-220 volts is now a steady 250 volts and my bill is up ~15%. The increased consumption is tied to how much I run the AC ...


3 phase AC to DC

Started by malua mada! in sci.electronics.basics2 years ago 5 replies

I am running 3 phase AC into a set of transformers, Y config, and thence into bridge rectifiers . One leg of the output side of the transformers...

I am running 3 phase AC into a set of transformers, Y config, and thence into bridge rectifiers . One leg of the output side of the transformers goes to the diodes. the other leg to the Y connection. That Y connection gets warm. (why?) Should it be connected to DC ground?