My 115V Hafler p3000 has a transformer wired as shown on the left.
Before I blow everything up, would someone please confirm that the rewiring for 230V as shown on the right is OK?
Thnks.
Before I blow everything up, would someone please confirm that the rewiring for 230V as shown on the right is OK?
Thnks.
Looks fine but to be sure you have the primary phased correctly you should power it with a dbt (dim bulb tester) first. If there were any issue the bulb keeps everything safe.
If there were a phasing issue you reverse the connection to one winding only (it doesn't matter which).
If there were a phasing issue you reverse the connection to one winding only (it doesn't matter which).
The beast is humming loud.
Using a 60hz transformer on 50hz mains does not seem like a good idea from what I gathered 🙁.
Using a 60hz transformer on 50hz mains does not seem like a good idea from what I gathered 🙁.
Possibly, it depends on the individual transformer. Some are OK and designed for both and some not. If it's buzzing loudly then it is being pushed into saturation. There is no easy fix for that, the input voltage would need to be reduced and that can't be done in an easy lossless way.
I find it WEIRD that the 115V example you have black and white wires connected the opposite way, but in any case use of a DBT will help you find the proper phase.
Also: Hafler is a serious Compny and if they provide a 230V option then it certainly must be 50Hz rated too.
So you may have yet another problem.
Disconnect all secondaries and retest.
Use a 100W bulb, what colour is the filament?
It should be red or barely orange, definitely not BRIGHT!!!
Also: Hafler is a serious Compny and if they provide a 230V option then it certainly must be 50Hz rated too.
So you may have yet another problem.
Disconnect all secondaries and retest.
Use a 100W bulb, what colour is the filament?
It should be red or barely orange, definitely not BRIGHT!!!
@JMFahey
Hafler does not propose the 230V option on the P3000 and therefore probably not the 50hz option either.
I just found by chance that my transformer model has a double primary connected as shown in the picture hence the initial post.
I have a hard time locating a 100W filament bulb to make a DBT. Only neon or led bulbs are sold here.
@Mooly
The Hafler transformer is humming too (amp fully operational) when operated with an external 230->115V transfomer.
Hafler does not propose the 230V option on the P3000 and therefore probably not the 50hz option either.
I just found by chance that my transformer model has a double primary connected as shown in the picture hence the initial post.
I have a hard time locating a 100W filament bulb to make a DBT. Only neon or led bulbs are sold here.
@Mooly
The Hafler transformer is humming too (amp fully operational) when operated with an external 230->115V transfomer.
Attachments
You could use a power resistor instead of the light-bulb. Could be 47 ohm 100W or similar, or a curling iron, or any similar heating device.
You would have to measure the voltage drop across the series resistor, ideally with the transformer disconnected from everything. If it's more than 10~20V, you have a problem.
Note that this type of transformer (named "cuirrassé" in french, but is probably not translatable as iron-clad) requires a good balance of the drive and load on each leg of the magnetic circuit.
In principle, series or parallel connections can achieve it properly, but if the secondaries are used with a center-tap full-wave rectifier, there might be imbalances during the cycle, causing unpleasant effects.
Using both sides separately is possible (I have done it), but you have to cope with a large leakage inductance, + buzzing and emission of stray fields when the load is heavy
You would have to measure the voltage drop across the series resistor, ideally with the transformer disconnected from everything. If it's more than 10~20V, you have a problem.
Note that this type of transformer (named "cuirrassé" in french, but is probably not translatable as iron-clad) requires a good balance of the drive and load on each leg of the magnetic circuit.
In principle, series or parallel connections can achieve it properly, but if the secondaries are used with a center-tap full-wave rectifier, there might be imbalances during the cycle, causing unpleasant effects.
Using both sides separately is possible (I have done it), but you have to cope with a large leakage inductance, + buzzing and emission of stray fields when the load is heavy
If the transformer buzzes with the correct 115v applied (measure it to make sure it is not actually higher than that) then either the transformer is just noisy with little you can do or the mains is very asymmetrical as that can cause a buzz.
Do try it as @JMFahey suggests with the secondaries not connected.
The transformer humms by itself at 120V, no secondaries connected.
According to google, P3000 transformer humm is a frequent problem and seems to have been cured in the later versions.
Mine is the older one with the horizontal power switch.
Still on the lookout for a 100W incandescent bulb
According to google, P3000 transformer humm is a frequent problem and seems to have been cured in the later versions.
Mine is the older one with the horizontal power switch.
Still on the lookout for a 100W incandescent bulb
Found an old 100W bulb !
Here is the result of my sunday morning experiment: connecting to 230V mains through DBT.
!Here is the result of my sunday morning experiment: connecting to 230V mains through DBT.
Ok,
In your case humming connection is fine, and non humming is wrong, it´s not humming only because its shorted because of wrong phase.
In fact, I am quite certain that you do not hear hum (a deep and smooth 50Hz frequency) but but buzz, a nasty bee/mosquito type sound, very different in quality.
Both have a 50Hz fundamental frequency but hum is quite pure, while buzz is full of much higher frequency harmonics.
For a transformer core to hum it needs to pass a lot of current (which is not happening, bulb is barely alight) because the whole core is expanding and contracting, while buzz comes from a couple loose laminations vibrating and touching each other, that takes very little power.
Heavily overdriven or shorted humming transformers typically blow mains fuses, buzz does not, it´s annoying but not destructive.
You might try to dunk transformer in varnish overnight, then hang from a broomstick between 2 chairs (put a can or lots of newspaper on the floor to catch varnish drops) until it dries.
In your case humming connection is fine, and non humming is wrong, it´s not humming only because its shorted because of wrong phase.
In fact, I am quite certain that you do not hear hum (a deep and smooth 50Hz frequency) but but buzz, a nasty bee/mosquito type sound, very different in quality.
Both have a 50Hz fundamental frequency but hum is quite pure, while buzz is full of much higher frequency harmonics.
For a transformer core to hum it needs to pass a lot of current (which is not happening, bulb is barely alight) because the whole core is expanding and contracting, while buzz comes from a couple loose laminations vibrating and touching each other, that takes very little power.
Heavily overdriven or shorted humming transformers typically blow mains fuses, buzz does not, it´s annoying but not destructive.
You might try to dunk transformer in varnish overnight, then hang from a broomstick between 2 chairs (put a can or lots of newspaper on the floor to catch varnish drops) until it dries.
I suspect you are going to struggle to eradicate the hum tbh based on what your tests show.
We used to do that kind of thing a lot with LOPTX's (TV line output transformers) and various ferrite parts along with small mains transformers in various items like clock radios. Mixed results you have to say. There is so much energy at a localised level within the core that silencing them is not always easy or possible. I would say if you do try it then first heat the transformer in a low heat oven (say 60C) and then dunk it in whatever potion you are going to use 😀
We used to do that kind of thing a lot with LOPTX's (TV line output transformers) and various ferrite parts along with small mains transformers in various items like clock radios. Mixed results you have to say. There is so much energy at a localised level within the core that silencing them is not always easy or possible. I would say if you do try it then first heat the transformer in a low heat oven (say 60C) and then dunk it in whatever potion you are going to use 😀
Thanks guys for your help and expertise.
When connected directly to 230V (without DBT) the humm/buzz is really loud. Not sure I want to fiddle with baking, soaking or torturing the old beast 🙂.
I don't want to keep listening to this noise and will investigate other solutions for the amp.
The transformer could be put to good use, together with 4 RD Tech modules, to build a beefy 4x 0-55V variable bench power supply, which does need to be totally silent.
When connected directly to 230V (without DBT) the humm/buzz is really loud. Not sure I want to fiddle with baking, soaking or torturing the old beast 🙂.
I don't want to keep listening to this noise and will investigate other solutions for the amp.
The transformer could be put to good use, together with 4 RD Tech modules, to build a beefy 4x 0-55V variable bench power supply, which does need to be totally silent.
With the correct connection (humm), a 100W lightbulb shouldn't begin to glow: the magnetizing current of a good transformer is well below the threshold.
This means that the iron is either of poor quality, or insufficient in core area for 50Hz. There is little you can do to address the problem
This means that the iron is either of poor quality, or insufficient in core area for 50Hz. There is little you can do to address the problem