still suffering with a bridge rectifier overheating

[AdhiWay]

Hi everyone, i posted three weeks ago about full bridge rectifier circuit "overheating of compenents problem" (diodes, mosfet, resistors), so im still suffering with this circuit,

i have old induction motor 220v/380v, it has a two electromagnetic coils specialised to pull a two metal cylinders, one coil pull one cylinder to connect it to the main rortor of the motor to make it rotates and the second coil pull the other cylinder to connect it to a fixed cylinder to make it stop, and these two coils work alternate,

and i believe that these two electromagnetic coils works with around 20v on DC power, because the motor had a complex circuit do Multiple tasks that is now broken and i dont need all those tasks now anyway, also it has a transformer 220v/24v and i didnt noticed when i posted my previous post that there is the amount of amperes written in transformer, it written "96 VA" if im correct it means 96 amperes,
so the problem that im facing is to convert the AC output of transformer to the DC without overheating of compenentes and without lossing power,
i tried anything according to my humble knowledge,
when i decrease the current the power become very weak and electromagnet is useless, and when i increase it the components start burning,
when i put high value resistors nothing changes in the decrease of current and when i put low value resistors they start burn,
i maked a transformerless circuit to decrease power, its input connected to the output of the main transformer and its output connected to the bridge rectifier input, and the result is very, very weak power that does not actuate the magnet, so i started to think of a way to increase it, so i connect another step-up transformer to the transformerless output and the result is no power at all in the step-up transformer output,
so i started to think of another way to feed the output of bridge rectifier connected to transformerless using mosfets to take power directly from the main transformer AC output to drop it in the output of the bridge rectifier using diodes, and two resistors and capacitors in series through each two gates of mosfets,, and the result is very very low increasing change, it almost nothing, but when i gived more power to the two mosfets gates by decreasing the value of resistors the power increased but again these mosfets begins overheated,
so no matter what i did always i end-up by one possibility, either i decrease power to prevent components from burning but the magnet coil will be useless or i make proper power for it but the compenents start burning,

now im thinking to build AC to DC to AC to DC circuit (multivibrator and switch mosfets), im thinking to decrease the bridge rectifier output power using resistors then converting it to AC then step-up it using transformer then converting the output step-up transformer to DC,
i drew the diagram of this circuit, so i would like and appreciate to hear your opinions and advice about this circuit, if it is correct or false,
and this is the link of my previous post : https://www.electronicspoint.com/fo...ut-full-bridge-rectifier.296879/#post-1826640
thank you all.

 

[kellys_eye]

96VA refers to the 'wattage' - your transformer (24VAC) has a maximum current of 4A.

If you are still using the 1N4007 diode note that it rated for 1A maximum.

You need to use rectifiers that have at least 5A capacity (better still, use an 8A or 10A diode). Normally, such individual diodes are not used and 'potted' bridge rectifiers are - the higher current devices are often built with heatsink pads too.

 

[Bluejets]

As well as the answer from #2, it still is unclear why you seem intent on running what we see as AC coils on DC.
As pointed out previously, the structure and physics are different and one is not suited to the other.

 

[kellys_eye]

and i believe that these two electromagnetic coils works with around 20v on DC power,

They might also work on the 24V AC supply directly - have you tried?

 

[AdhiWay]

96VA refers to the 'wattage' - your transformer (24VAC) has a maximum current of 4A.

If you are still using the 1N4007 diode note that it rated for 1A maximum.

You need to use rectifiers that have at least 5A capacity (better still, use an 8A or 10A diode). Normally, such individual diodes are not used and 'potted' bridge rectifiers are - the higher current devices are often built with heatsink pads too.

thank you,
i did tested it directly with the AC output of the transformer 24v, and the result is weak magnet it does not pull the metal cylinder, also the cylinder start vibrating because of the AC alternate i think, so that it shows clearly either the coils work with DC or the transformer 24v AC output must step-uped
and if diodes are not usefull in this application so what do you think the solution for this?

 

[AdhiWay]

As well as the answer from #2, it still is unclear why you seem intent on running what we see as AC coils on DC.
As pointed out previously, the structure and physics are different and one is not suited to the other.

thank you,
brother, i did tested it directly with the AC output of the transformer 24v, and the result is weak magnet it does not pull the metal cylinder, also the cylinder start vibrating because of the AC alternate i think, so that it shows clearly either the coils work with DC or the transformer 24v AC output must step-uped
take a look of how the cylinder look like

 

[Bluejets]

Where did the "coils" originate..?
Were they part of the transformer to begin with or did you drag them out of the dump somewhere?
Until now I was assuming it was all part of the same device.
Like trying to sqeeze blood out of a stone.....

 

[Martaine2005]

and if diodes are not usefull in this application so what do you think the solution for this?

Are you still using 1N4007 diodes?
If so, the solution has been given.

Martin

 

[AdhiWay]

Where did the "coils" originate..?
Were they part of the transformer to begin with or did you drag them out of the dump somewhere?
Until now I was assuming it was all part of the same device.
Like trying to sqeeze blood out of a stone.....

(did you drag them out of the dump somewhere?), come on brother, im trying to have serious conversation with you, and if i did drag them out of the dump somewhere, then i will tell you,
it seems with all conversations we have you still didnt understand!,
the coils, transformer and all the pieces that i showned before are origine with the motor,
the main rotor of the motor are separate of the electronic system that runs the coils and other tasks, and it work directly with 220v/380v AC, also the 220v AC goes to a box installed in the outside of the motor, and goes directly to the transformer that i showed before, and from the output of transformer the power goes to a big complex circuit that also exist inside the box with the transformer and from this circuit the power goes to the coils and other tasks related to the machine that this motor runs,
the machine is a sewing machine, this motor is original for a sewing machine, and the other tasks is like : cutting the sewing thread automatically, moving some pieces inside sewing machine ect....,
but the coils that we are talking about they has only two jobs, they pull two cylinders one of them for to connect it to the main rotor to make the second rotor runs and the other connect the second cylinder to a fixed cylinder to make the second rotor stops "braking"

 

[AdhiWay]

Are you still using 1N4007 diodes?
If so, the solution has been given.

Martin

yes i understand that these diodes maximum 1A and the amperage of the power source are much higher, so if that the case i would like to hear an opinion about how it resolve this problem, to give the coils power that needs to work proparly without overheating the components,
the problem is according to all test i did the coils must feed with high DC power im not sure the exact amperes but definitely above 1A, 3A...., so im confused,
and now im thinking to make this ciruit that i posted here about (DC to AC step-up), so im trying to hear opinions from the members if this circuit correct or not before i star to build it, because the circuits take times and focus, also i use only old electronic compenents, so there is a lots of work,
so what do think about this circuit?

 

[Martaine2005]

yes i understand that these diodes maximum 1A

Please read all the comments especially post #2.
Forum members won’t keep repeating themselves.

Martin

 

[kellys_eye]

The coils are an electric clutch and an electric brake. They work by creating a large magnetic field across the face of the plates attached to them and even a 'weak' field will cause one plate to 'attach' to another.

Some sewing machine motors use a mechanical clutch to give a 'variable drive' effect - operated by a mechanical linkage from a foot pedal to the clutch plate - whilst yours seems to be an electrical version.

Post some pics of the original circuitry that controlled these clutches (i.e the stuff in the box with the transformer). It is quite likely to be a simple variable voltage device with a foot pedal input.

Please note that your inability to understand how the original system works doesn't help us to decipher your description of how you think it works.

You must also read what we post. The answer to the diode issue has been made already.

 

[bertus]

Hello,

Also one remark on the multivibrator.
At 16 volts the transistors will break due to over voltage during discharge.
Read this page for more info:
https://www.nutsvolts.com/magazine/article/bipolar_transistor_cookbook_part_6

From the page:
Outputs can be taken from either collector, and the two outputs are in anti-phase.
The Figure 1 circuit’s operating frequency is almost independent of supply-rail values in the range 1.5 V to 9.0 V;
the upper voltage limit is set by the fact that, as the transistors change state at the end of each half-cycle,
the base-emitter junction of the off one is reverse biased by an amount almost equal to the supply voltage
and will zener (and upset the timing action) if this voltage exceeds the junction’s reverse breakdown voltage value (which is typically about 10 V).

As for the diodes, you could use a power bridge rectifier like in the following add:
https://www.tradewheel.com/p/kbpc5010-50a-1000v-diode-bridge-rectifier-286074/

Bertus

 

[AdhiWay]

Hello,

Also one remark on the multivibrator.
At 16 volts the transistors will break due to over voltage during discharge.
Read this page for more info:
https://www.nutsvolts.com/magazine/article/bipolar_transistor_cookbook_part_6

From the page:
Outputs can be taken from either collector, and the two outputs are in anti-phase.
The Figure 1 circuit’s operating frequency is almost independent of supply-rail values in the range 1.5 V to 9.0 V;
the upper voltage limit is set by the fact that, as the transistors change state at the end of each half-cycle,
the base-emitter junction of the off one is reverse biased by an amount almost equal to the supply voltage
and will zener (and upset the timing action) if this voltage exceeds the junction’s reverse breakdown voltage value (which is typically about 10 V).

As for the diodes, you could use a power bridge rectifier like in the following add:
https://www.tradewheel.com/p/kbpc5010-50a-1000v-diode-bridge-rectifier-286074/

Bertus

i really forget completely these cube bridge rectifier, i have an old one or two of them somewhere in the house i will search of them to test it, thank you
and about your remark on the multivibrator, circuits, i understand that i should decrease more the voltage,
Sometimes i find difficult to understand when electronics terms it use it

 

[AdhiWay]

The coils are an electric clutch and an electric brake. They work by creating a large magnetic field across the face of the plates attached to them and even a 'weak' field will cause one plate to 'attach' to another.

Some sewing machine motors use a mechanical clutch to give a 'variable drive' effect - operated by a mechanical linkage from a foot pedal to the clutch plate - whilst yours seems to be an electrical version.

Post some pics of the original circuitry that controlled these clutches (i.e the stuff in the box with the transformer). It is quite likely to be a simple variable voltage device with a foot pedal input.

Please note that your inability to understand how the original system works doesn't help us to decipher your description of how you think it works.

You must also read what we post. The answer to the diode issue has been made already.

yes, the majority of sewing machine has a pedal attached to a mechanical arm of the motor, in old motors this system was completely mechanical, and they has two separate rotor, the main rotor which turn-on as soon we push the power button but the second rotor keeps stopping which it has the Pulley that is connected to sewing machine with V-belt, so when we trample on the pedal we make the mechanical arm moves which cause the clutch plate of second rotor moves to attaches the main rotor plate that is already running which makes sewing machine runs throught the V-belt,

but this motor that we are talking about is from the first generation of electronic sewing machine motors, so the difference is just that mechanical system of acceleration and braking replased by two electromagnet to do it, and more electricity consumption, and the counter counts over the month, hhh,

notice : my profession is sewing machine mechanics,
but as for electricity, i never study or searched it, i knew very simple things about electricity until recently i started to search about its basics trying to learn, i all my life interested on electronics,
also sometimes i find difficult to understand when electronics terms it use it,

this is more details pictures of the motor, circuits and its peices,


this is the whole motor with its box, and the four wires are of the two magnet coils.



this is from behind where the main input that runs the motor and goes to the box too.


this is the main motor without the box and the second rotor which the two magnet coils exist.


this is the box and these wires are 220v that goes to the transformer inside to the circuits, and you can see the arm in left which is connected to the pedal that is on the machine table.



this is the circuit inside.


this is what exist under the circuit, the transformer and another circuit that maybe convert AC to DC, and you can see that those two black wires in the left are the 220v input, and the two black wires in the right that is connecting to the circuit are output, and that yallow wire, i puted it there because there is a fuse seems broken,
this is all, and thank you i apreciate.

 

[kellys_eye]

In the bottom picture, under the yellow wire, there is a three pin device fitted to a heatsink. What is the part number on that device? Can you post a close-up picture of the whole board?

I suspect it is part of a simple regulating circuit to develop the voltage to drive the coil(s) and, knowing the part numbers and layout, we can determine the required voltage and/or offer advice on how to test/repair it if there is an issue.

As for the rest of the unit, the electronics in it lead me to believe that the whole device is more likely to be part of an embroidery unit - something that can sew complicate patterns in a semi-automated fashion.

 

[AdhiWay]

In the bottom picture, under the yellow wire, there is a three pin device fitted to a heatsink. What is the part number on that device? Can you post a close-up picture of the whole board?

I suspect it is part of a simple regulating circuit to develop the voltage to drive the coil(s) and, knowing the part numbers and layout, we can determine the required voltage and/or offer advice on how to test/repair it if there is an issue.

As for the rest of the unit, the electronics in it lead me to believe that the whole device is more likely to be part of an embroidery unit - something that can sew complicate patterns in a semi-automated fashion.

this motor comes with industrial single needle lockstitch sewing machine and sometimes with two needle lockstitch sewing machine,
this device has nothing to do with sew complicate patterns,
this device do some tasks like runs those coils,
lifting pressure foot automatically,
cut sewing thread automatically after lifting pressure foot,
like always making the needle in elevated position automatically when the machine stops, not inside the hole of the machine,
thats pretty much all the device does.
notice : i don't need these tasks, i will remove the big circuit in the previous pics, because the sewing machine that im trying to make this motor work with it doesnt have the pieces that work with this system, it completely mechanical machine, all i need it just to make the magnet coils work properly for running and braking, thank you for helping.

 

[kellys_eye]

Just from observation of the top side of the board, the AC from the transformer goes onto the board at #1 and #2, is fed to the bridge rectifier block (grey lump rated at 40V and 5A), smoothed by the big capacitor and then to the regulator IC LM317 whose output voltage is set by two resistors connected to the 'adjust' pin (see the data sheet for the LM317 for details). I can't see which of the resistors is setting the voltage but suspect it may be around 28VDC - the maximum current the LM317 can deliver is 1.5A. The output current may be regulated/limited since there is another transistor and LED in there but I can't tell....

This regulated DC voltage looks to go out at #4 and #5 (can't see). Either way, all the generated voltages seem to go out on #4 to #7 inclusive.

In addition, the 24VAC at #1 and #2 is also rectified by the two diodes under pin #2 and an UNregulated DC is fed (probably at around 36V) to two of the other pins (#6 and #7 again, I can tell from the pics).

Whatever - all you have are two DC voltages, one regulated, one unregulated which are of relatively low current - 1.5A max for the regulated, possible 2A or 2.5A for the unregulated. If these go to your coils then we can be assured that they will work with only 24-28V DC on them.

This is all assumption given I can only see one side of the board and not all the pin numbers or track runs......

Where do the wires at 4, 5, 6 and 7 go? Can you show the other side of the board as well?

 

[AdhiWay]

Just from observation of the top side of the board, the AC from the transformer goes onto the board at #1 and #2, is fed to the bridge rectifier block (grey lump rated at 40V and 5A), smoothed by the big capacitor and then to the regulator IC LM317 whose output voltage is set by two resistors connected to the 'adjust' pin (see the data sheet for the LM317 for details). I can't see which of the resistors is setting the voltage but suspect it may be around 28VDC - the maximum current the LM317 can deliver is 1.5A. The output current may be regulated/limited since there is another transistor and LED in there but I can't tell....

This regulated DC voltage looks to go out at #4 and #5 (can't see). Either way, all the generated voltages seem to go out on #4 to #7 inclusive.

In addition, the 24VAC at #1 and #2 is also rectified by the two diodes under pin #2 and an UNregulated DC is fed (probably at around 36V) to two of the other pins (#6 and #7 again, I can tell from the pics).

Whatever - all you have are two DC voltages, one regulated, one unregulated which are of relatively low current - 1.5A max for the regulated, possible 2A or 2.5A for the unregulated. If these go to your coils then we can be assured that they will work with only 24-28V DC on them.

This is all assumption given I can only see one side of the board and not all the pin numbers or track runs......

Where do the wires at 4, 5, 6 and 7 go? Can you show the other side of the board as well?

im stupid, if you imagine, from the day that i get this motor i didn't measure any of these circuits, i was focusing from day one to remove this system and make simple circuit to drive the coils, because like i said i dont need those tasks,
but now after when i removed this circuit to show you pics, i thought to measure it with multimeter and it seems working, maybe the whole problem even before i get the motor was in that transformer fuse,
but now i was about to ask you about the 4 wires (4, 5, 6, 7) that you ask me just now, it seems all of them gives voltage reading in multimeter on DC option, not on AC, but the problem no matter i changed the wires of multimeter (VΩ and com) between those 4 wires the mutimeter gives voltage reading, is like the output is AC but when i change the multimeter option to AC it doensnt gives V reading.
this is pics of the 4,5,6,7 that you asked



these two hole on left are empty







this pics of the circuit seems working also the measuring, even i changed the wires of multimeter (VΩ and com) between those 4 wires the mutimeter gives voltage reading!!

 

[kellys_eye]

Please read the posts.

I was referring to the numbered connections ON THE BOARD. I don't know if those numbers even correspond to where you are measuring???? so how can I determine right/wrong from that?

Show a picture of the BOARD, top side and bottom side and measure the voltage ON THE BOARD.

You should have 24V AC at #1/#2 and at the bridge rectifier (the pins marked ~).
You should have (about) 33-35V DC at the +/- of the bridge recitifier.
You will have 'something' (DC) at #4/#5/#6/#7.

What do you get?