If it is taking 200mA on 220V setting, and 100mA on 240V setting, then it is probably suffering from core saturation due to being run unloaded. Some cheaper transformers (and some expensive ones?) run too close to the limit (or just over the edge) when unloaded. Try adding a realistic load, preferably via a lamp limiter.
I have made one more test.
I have use output (325V) coil as primary. It takes only 14mA.
DF96 is right ! It is core saturation.
thanks
temporally I will use it as is but I am going to buy new one
maybe I will buy this one https://www.edcorusa.com/p/590/xpwr002_240
What do you think about ?
I have use output (325V) coil as primary. It takes only 14mA.
DF96 is right ! It is core saturation.
thanks
temporally I will use it as is but I am going to buy new one
maybe I will buy this one https://www.edcorusa.com/p/590/xpwr002_240
What do you think about ?
A bit of Googling showed me that this supplier (MPS) has recently opted to get his transformers made in China. They may be cutting corners on the winding, or the core. MPS might not realise this. I would report your findings to MPS (who appear to be away at present according to their ebay shop). See what they say. Bear in mind that with transformers you broadly get what you pay for, and MPS appearsto be one of the cheaper makes.
PT325.2i - 44$
XPWR002-240 - 57.33$
PT325.2i ~62W
XPW002-240 ~140W
Accordingly to this the price per watt of PT325.2i is higher
Am I right ?
Transformer prices don't necessarily scale $/W.
Anyway, there is clearly something not quite right. It could be a shorted turn, but I think saturation is more likely. Maybe the factory got confused and built it with an core airgap. Or maybe they just used too few turns (quicker so cheaper to build). Maybe they sent you a 120V primary by mistake.
Anyway, there is clearly something not quite right. It could be a shorted turn, but I think saturation is more likely. Maybe the factory got confused and built it with an core airgap. Or maybe they just used too few turns (quicker so cheaper to build). Maybe they sent you a 120V primary by mistake.
how big is your traffo? core area? 200mA is not such a big deal if that is a big traffo....high exciting current is an indication of fewer primary turns...not all of this current heats up your traffo...
how hot is hot? can you touch it for 5 seconds without your hand feeling pain?
that's one hot traffo, what is your ambient temp? if 25*C then that is just a 25*C temperature rise, not too far off...
a saturated transformer will burn out and emit smoke by itself...
if you are able to run your traffo without load without bringing out smoke, then it is probably the nature of that traffo....to me a traffo that heats up on idle is one traffo that has not enough primary turns so that idle current is higher otherwise....
Just signed up here at DIYAudio to participate in this discussion. He's caught us with the EBay store closed for vacation and offline until today. My apologies for the poor timing.
I had asked WKNIGHT to provide a reading off the heater windings to assure that he did not get a 120Vac version by mistake. His results were:
6.3vac -> 6.85vac without load
6.3vac -> 6.6vac with 1.5A load
So he has the right primary. If there was a shorted turn the PT would heat up and fail quickly. The core is a 1x1 interleave of 29M6 laminations, so air-gap would not be an issue.
The PT325.2, PT275.2 & PT190.2 families have consistently been built to an MPS design since 2009 using the same manufacturer and several hundred have been sold and used successfully in Amp builds from 0.5W to 25W. The "0.2" indicates a second generation design, where enhancements were made in 2008 to increase heater outputs and increase primary turns to reduce saturation losses.
Upon receipt in the USA, each PT is inspected, installed into USA made end bells with Stainless hardware and tested at no-load and loaded operating conditions before packing. Admittedly the 220/240v versions are a minority of the MPS business, but around 75pcs of this version have been sold and used successfully. I'm confident in the source, construction and processes used.
Sunday night I can get a comparison exitation current reading on a regular PT325.2. I'd agree that 122F is quite warm. In the normal set-up load testing the load resistors run that hot....but the transformer temp rise is negligable. If there's something wrong here, we'll get another one out to him.
I had asked WKNIGHT to provide a reading off the heater windings to assure that he did not get a 120Vac version by mistake. His results were:
6.3vac -> 6.85vac without load
6.3vac -> 6.6vac with 1.5A load
So he has the right primary. If there was a shorted turn the PT would heat up and fail quickly. The core is a 1x1 interleave of 29M6 laminations, so air-gap would not be an issue.
The PT325.2, PT275.2 & PT190.2 families have consistently been built to an MPS design since 2009 using the same manufacturer and several hundred have been sold and used successfully in Amp builds from 0.5W to 25W. The "0.2" indicates a second generation design, where enhancements were made in 2008 to increase heater outputs and increase primary turns to reduce saturation losses.
Upon receipt in the USA, each PT is inspected, installed into USA made end bells with Stainless hardware and tested at no-load and loaded operating conditions before packing. Admittedly the 220/240v versions are a minority of the MPS business, but around 75pcs of this version have been sold and used successfully. I'm confident in the source, construction and processes used.
Sunday night I can get a comparison exitation current reading on a regular PT325.2. I'd agree that 122F is quite warm. In the normal set-up load testing the load resistors run that hot....but the transformer temp rise is negligable. If there's something wrong here, we'll get another one out to him.
Currently I don't have a great AC Ammeter on hand. I am getting about 100 to 120mA ac no load current on the PT190.2, PT275.2 and PT325.2 transformers reading on a 10A scale. They all have the same primary and core, so I'd expect they'd run close. The temp rise though is under 5C though. Putting my load test resistors on the HiV windings and pulling another 200mA Ac on the primary and there's still no significant temp rise.
If you get some more precise readings on the PT275.2 please share.
So there is likely something wrong with the unit WKnight has. It's possible the HiV windings are seeing some turn-to-turn arcing or shorting. A quick overload or voltage spike could potentially cause that type of issue without a dead short. It's hard to tell without measuring output voltage under load.
I've sold out the original 25pc lot of PT325.2i's from China, so I'll build one here in the US and send it off to WKnight. We'll see if this resolves the heat-up issue. We don't want him using that PT as-is.
Matt
If you get some more precise readings on the PT275.2 please share.
So there is likely something wrong with the unit WKnight has. It's possible the HiV windings are seeing some turn-to-turn arcing or shorting. A quick overload or voltage spike could potentially cause that type of issue without a dead short. It's hard to tell without measuring output voltage under load.
I've sold out the original 25pc lot of PT325.2i's from China, so I'll build one here in the US and send it off to WKnight. We'll see if this resolves the heat-up issue. We don't want him using that PT as-is.
Matt
What I will do when I have the time is to plot the excitation current vs. input voltage. This should be linear. If you're near stauration, the excitation current will take a sharp jog upward as you increase input voltage. This is the behavior I noticed with the 275-2. I will quantify it a bit better. I also have a Hammond rated for somewhat higher power (270FX), and it will get the same treatment
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.