Thank you all for the kind comments and happy new year! One note to add to avoid confusion: Instead of thinking in terms of parallel/series of winding, we can note that the input consists of an auto-transformer followed by a regular two-coil transformer. The auto-transformer provides variable ratio while the regular transformer provides the isolation. Please note that the auto-transformer itself provides no isolation as it only has a single coil where all three terminals are electrically connected.
I'm wondering if there's a particular reason why the two transformers are that way round: I'm putting a separate Variac and isolation transformer together myself, and I can't think of any reason why the isolation transformer could not come before the Variac, which is actually more convenient for my setup. Are you aware of any reason the Variac should come first?
@@pdgiddie My opinion: There are advantages and disadvantages for both arrangements. The isolation transformer is probably designed for 120 V input, and feeding it from a variac operating in step-up mode with an output of 130-150V could push the isolation transformer into saturation, causing it to run hot. The Sencore isolation transformer should be specified for 140 V input, but a random isolation transformer likely isn't. (This isn't an issue if you only use the variac in step-down mode). Wiring the isolation transformer first means it never sees more than normal line voltage. On the other hand, an isolation transformer designed for electronic service has a completely isolated secondary circuit, with insulation that's probably designed and tested for a large voltage difference between input and output (Hammond 171 series are tested to 2000 VRMS). Wiring the isolation transformer after the variac means that the variac is operating under normal AC circuit conditions, with at most a few volts difference between neutral and ground, while only the isolation transformer has to deal with the secondary possibly being hundreds of volts away from ground. If you wire them with the isolation transformer first, then the whole variac is part of the isolated secondary circuit and should be able to withstand hundreds of volts between its neutral and ground without current leakage or arcing. If the variac is well made, it may be fine in this situation, but it probably wasn't designed or tested for use under those conditions.
Whenever I need an isolated mains socket, I use one of those cheap car invertors that make 120V AC out of 12V DC. I get 12V for it from my lab power supply. The resulting AC is not the best in shape, but fits most of the purposes such as fixing the power supply of some home consumer electronics.
Remarkably similar in design to a variable isolation supply I am building. I put a load resistor that I can switch in series with the output to protect against a short in the DUT. I used commercially made voltmeter and ammeters for monitoring, and a bar graph indicator to show voltage across the load resistor. The variable voltage is via a variac which is a variable auto transformer, same as in your unit.
Sencore had a parallel company called BAPCO. The equipment was in the biomedical market. A 20amp version of the PR570 was produced. I found 2 for my audio amplifier shop!
I have a question I'd like to throw out. I have a Heatkit IP-5220, same basic design, simpler metering. The topology is the same, Variac first from the mains, then the isolation transformer, to the power outlets on the front of the unit. There is also a direct non-isolated utility outlet on the front. The main fuse for the unit is 7 amps. The variac is rated for 3 amps. Output metering/fusing is switchable for 1 or 3 amps. Just want to give as much info as possible about the unit. What I would like to do is reconfigure it so that the iso trans comes first, the output of that goes to both the variac and one of the power outlets to provide direct line voltage isolation,. The out put of the variac to the other power outlet for variable voltage. The question is, will I run into trouble swapping the order of the variac and iso trans? What considerations go into putting them in a particular order?
If I designed that for the 110-120 volt market, I would have made the main transformer into a 1:2 turns ratio, so that one could output 220-240 +the extra that the variable transformer gives. Maybe split the 1:2 ratio into two taps, so one could select 1:1 or 1:2, so we could use thicker wire for the 1:1 to get better current carrying capability if needed.
Parallel/serial does not apply. The variac output supplies the isolating transformer primary. Also, the variac is an autotransformer - it does not have a primary or secondary and therefore does not have a turns ratio, it has a tapping ratio.
Instead of thinking in terms of parallel/series of winding, we can note that the input consists of an auto-transformer followed by a regular two-coil transformer. The auto-transformer provides variable ratio while the regular transformer provides the isolation. I added a note to the video to avoid confusion. Please note that the auto-transformer itself provides no isolation as it only has a single coil where all three terminals are electrically connected.
Jay Walt my Patreon account is based on episode production. But I didn't want to charge my supporters for the "short" videos, so I won't apply those to the Patreon account. You can tell which videos are marked short by the name of the video.
Hi. I wonder if there are other options than this PR570 available on the market or used? I am primarly interested in 230V input and 0V-270V output. 1000VA would be enough. Something that has nice display with all measurements shows at the same time, less knobs, and active output regulation, so the output is stable even if the input varies, and output relay cutoff if the regulation can't be performed. The PR570 is really dated, looks like a design from 80s probably. And it doesn't have active regulation. So you probably should stick input it into inverter or automatic voltage regulator. The PR570 also looks like a really low power, maybe 400W? That can be done this days easily using solid state inverter instead with very little cooling.
Oh oops, I must have blacked out during that bit, all I remembered was you mentioning they turned out not having a zebra connector. Watching it again and of course now I hear it. Thanks!
Are you sure about the fact that the iPhone charger is a buck converter? Considering that it is easy to access its terminals, some kind of isolation is definitely needed for people's safety. I'm voting for a flyback but I'm not sure. Can you confirm this? Thanks
It's alive, thank goodness!
Oh hello there Marco!
Thank you all for the kind comments and happy new year! One note to add to avoid confusion:
Instead of thinking in terms of parallel/series of winding, we can note that the input consists of an auto-transformer followed by a regular two-coil transformer. The auto-transformer provides variable ratio while the regular transformer provides the isolation. Please note that the auto-transformer itself provides no isolation as it only has a single coil where all three terminals are electrically connected.
I'm wondering if there's a particular reason why the two transformers are that way round: I'm putting a separate Variac and isolation transformer together myself, and I can't think of any reason why the isolation transformer could not come before the Variac, which is actually more convenient for my setup. Are you aware of any reason the Variac should come first?
@@pdgiddie My opinion: There are advantages and disadvantages for both arrangements.
The isolation transformer is probably designed for 120 V input, and feeding it from a variac operating in step-up mode with an output of 130-150V could push the isolation transformer into saturation, causing it to run hot. The Sencore isolation transformer should be specified for 140 V input, but a random isolation transformer likely isn't. (This isn't an issue if you only use the variac in step-down mode). Wiring the isolation transformer first means it never sees more than normal line voltage.
On the other hand, an isolation transformer designed for electronic service has a completely isolated secondary circuit, with insulation that's probably designed and tested for a large voltage difference between input and output (Hammond 171 series are tested to 2000 VRMS). Wiring the isolation transformer after the variac means that the variac is operating under normal AC circuit conditions, with at most a few volts difference between neutral and ground, while only the isolation transformer has to deal with the secondary possibly being hundreds of volts away from ground. If you wire them with the isolation transformer first, then the whole variac is part of the isolated secondary circuit and should be able to withstand hundreds of volts between its neutral and ground without current leakage or arcing. If the variac is well made, it may be fine in this situation, but it probably wasn't designed or tested for use under those conditions.
I like the human interface of this device, everything is so nicely and so clearly labeled.
wow. finally updated. could you do a tour of your new home lab ?
Chenxiang Hsu sure. As soon as it is setup.
Whenever I need an isolated mains socket, I use one of those cheap car invertors that make 120V AC out of 12V DC. I get 12V for it from my lab power supply. The resulting AC is not the best in shape, but fits most of the purposes such as fixing the power supply of some home consumer electronics.
Great to have you back again...very Happy New Year!
A very good new year and good to have you back again with new videos.
These are great isolation transformers; bought mine years ago. "Excellent presentation" you won't be disappointed with this gem.
So good to see you back, Happy new year!!!
Remarkably similar in design to a variable isolation supply I am building. I put a load resistor that I can switch in series with the output to protect against a short in the DUT. I used commercially made voltmeter and ammeters for monitoring, and a bar graph indicator to show voltage across the load resistor. The variable voltage is via a variac which is a variable auto transformer, same as in your unit.
So happy to have you back
Thanks Sir , I'm happy to see you back with new project again..Wish you a happy prosperous start on the new year
Happy new Year!! nice to see you back :)
Nice to have you back. Really looking forward to all the nice videos that will be coming.
Yay, The SignalPath Video! What a great beginning of 2017 :) Wish you all the best, and more great vid's ;).
Sencore had a parallel company called BAPCO. The equipment was in the biomedical market. A 20amp version of the PR570 was produced. I found 2 for my audio amplifier shop!
I'm looking forward to seeing more tests using the Sencore unit.
As a longtime subscriber I am pleased to become a patreon supporter of your channel!
Great to see you again....
YAY!!1 HAPPY TO HAVE YOU BACK, SHARIAR!
Nice to see you back ☺
Welcome back and happy new year
Happy New year Shahryar, finally updated. please also post a video about high speed PCB simulation software tutorial.
Glad to see you back,
Glad to see you back :) I love your repair videos.
Another great video, Thanks Shahriar!
I have a question I'd like to throw out. I have a Heatkit IP-5220, same basic design, simpler metering. The topology is the same, Variac first from the mains, then the isolation transformer, to the power outlets on the front of the unit. There is also a direct non-isolated utility outlet on the front.
The main fuse for the unit is 7 amps. The variac is rated for 3 amps. Output metering/fusing is switchable for 1 or 3 amps. Just want to give as much info as possible about the unit.
What I would like to do is reconfigure it so that the iso trans comes first, the output of that goes to both the variac and one of the power outlets to provide direct line voltage isolation,. The out put of the variac to the other power outlet for variable voltage.
The question is, will I run into trouble swapping the order of the variac and iso trans? What considerations go into putting them in a particular order?
hey. welcome back:) we missed u.
Very good information on all your videos.
Have a great new year
Happy new year. Welcome back ;-)
do you use deoxit fluid on pots and crusty conections? it works very well.
welcome back and New Year!
If I designed that for the 110-120 volt market, I would have made the main transformer into a 1:2 turns ratio, so that one could output 220-240 +the extra that the variable transformer gives. Maybe split the 1:2 ratio into two taps, so one could select 1:1 or 1:2, so we could use thicker wire for the 1:1 to get better current carrying capability if needed.
Happy new year!
Does it matter whether you put the variable transformer on the primary or the secondary side of the isolation transformer?
No and in fact if you put the variable transformer after the safety isolating transformer, you can double-isolate the control electronics as a bonus.
welcome back.
What makes the variac and main transformer to be in parallel? I would call it serial.
Parallel/serial does not apply. The variac output supplies the isolating transformer primary. Also, the variac is an autotransformer - it does not have a primary or secondary and therefore does not have a turns ratio, it has a tapping ratio.
Instead of thinking in terms of parallel/series of winding, we can note that the input consists of an auto-transformer followed by a regular two-coil transformer. The auto-transformer provides variable ratio while the regular transformer provides the isolation. I added a note to the video to avoid confusion. Please note that the auto-transformer itself provides no isolation as it only has a single coil where all three terminals are electrically connected.
Well come back! Thumbs up.....PEACE
Hey mate, Siglent Spec Analyzer review coming?
welcome back
Oi vey! I thought you were dead... after waiting like 6 million years!
I like your videos, senpai ~
Can you please share the schematic if the devices you showing in the video ?
I found the op manual here which contains the circuit diagram.
drco.pairserver.com/manuals/PR570-OSM.pdf
Finally , I had gone through withdrawal from being addicted to your channel ;)
Now I will be hooked again , doggy dew ;)
It's a shame there doesn't appear to be a 240VAC version of this unit.
Finaly a new video
Hello Shariar, is there any replacement for this device (something similar like that)? This one is too hard to find anywhere. Thank You
This is discontinued unfortunately. I am repairing another unit to replace this one in my lab. It is a very sophisticated unit if I can fix it.
@@Thesignalpath There will be video of this repair?
@@astalavistatomi Yes.
Yes, but what happens when you try to charge your iPhone with 300v?
mark putham not good things. ;)
What do you mean "short videos will not be charged to patreon"?
Jay Walt my Patreon account is based on episode production. But I didn't want to charge my supporters for the "short" videos, so I won't apply those to the Patreon account. You can tell which videos are marked short by the name of the video.
Hi. I wonder if there are other options than this PR570 available on the market or used? I am primarly interested in 230V input and 0V-270V output. 1000VA would be enough. Something that has nice display with all measurements shows at the same time, less knobs, and active output regulation, so the output is stable even if the input varies, and output relay cutoff if the regulation can't be performed. The PR570 is really dated, looks like a design from 80s probably. And it doesn't have active regulation. So you probably should stick input it into inverter or automatic voltage regulator. The PR570 also looks like a really low power, maybe 400W? That can be done this days easily using solid state inverter instead with very little cooling.
is it just me or was the repair part totally missing? either way thankful for a new video
Jon Sands I am sorry, I explained in the video that all I had to do was to re-insert the LCD module to fix the contact problem.
Oh oops, I must have blacked out during that bit, all I remembered was you mentioning they turned out not having a zebra connector. Watching it again and of course now I hear it. Thanks!
This is quite a surprise. I thought you had vanished into a distant sunset never to return.
cat still being a cat as per usual, things seem good.
Are you sure about the fact that the iPhone charger is a buck converter?
Considering that it is easy to access its terminals, some kind of isolation is definitely needed for people's safety. I'm voting for a flyback but I'm not sure.
Can you confirm this? Thanks
Hatimoooo I think you are right. It is definitely transformer based.
I wish I can effort one
11:23
Kitty
👍👍
omg. Yay!
Your cat is defective. They're supposed to stop right in front of the camera.
"it's functional, but it has a small problem" and that works how exactly?
woo hoo
You are still speaking far too quickly - SLOW DOWN please!
I am sorry, this is my normal speaking speed. :(