what are these components?

[mike-gr]

Hello everyone!
I want to ask the old guys in here if they know what are these components on the photos no 2 & 3?
These things are part of the electrical system of an old hydraulic "clicker" press. It's used to cut leather,paper etc. The machine is probably from the 70's and there is no tag on it so i don't know any infos!
It's working ok but i am thinking to either change the 3 phase electric motor with a new single phase motor or make this one single phase! My problems are these 2 components! I don't know how they will be affected from this change! The machine have 2 handles with one button each. To make the head move downwards you must press both buttons (i guess as a security measure so that you always have both hands safe). The buttons are connected with this component. I know there is a big electromagnet in the head (next to the buttons) that moves a lever that actuates the downwards move of the head.
I already asked the company but they don't have any pdf for this machine anymore!

 

[mike-gr]

A better photo of the trasformer!

 

[pc1966]

If there are likely to be big issues in converting from 3-phase to single you might want to look at getting a static converter to generate 3-phase from your single phase supply.

 

[mike-gr]

If there are likely to be big issues in converting from 3-phase to single you might want to look at getting a static converter to generate 3-phase from your single phase supply.

That's the other way around! I have to check this too!

 

[Lucien Nunes]

It's worth mentioning that a 230V transformer to do this job will not be massively expensive, but it will be important to discover the output voltage of the present one. If you are equipped to work safely on live equipment you could measure the AC voltage between terminals 1 & 2 which is the transformer supply. If it is 400V and you need to replace the transformer, then measure between terminal 12 and wire 16 with the buttons pressed, which the secondary voltage and is more likely to be 24V or similar. Then, disconnect the brown wire from terminal 6, connect your meter on AC amps between the terminal and the wire, and press the buttons to complete the circuit and confirm the secondary load current.

 

[mike-gr]

It's worth mentioning that a 230V transformer to do this job will not be massively expensive, but it will be important to discover the output voltage of the present one. If you are equipped to work safely on live equipment you could measure the AC voltage between terminals 1 & 2 which is the transformer supply. If it is 400V and you need to replace the transformer, then measure between terminal 12 and wire 16 with the buttons pressed, which the secondary voltage and is more likely to be 24V or similar. Then, disconnect the brown wire from terminal 6, connect your meter on AC amps between the terminal and the wire, and press the buttons to complete the circuit and confirm the secondary load current.

Now i am beginning to have an idea of what is happening! I will try to do the measurement with an electrician friend!

 

[mike-gr]

Just a thought! What if i use a power supply to transform and rectify the current and feed this to the buttons?

 

[Lucien Nunes]

That is possible too, but depending on the voltage a relay might be needed because the buttons (which switch AC at the moment) might not be suitable to switch the DC. (they are on the AC input side of the rectifier for good reason). In any case, either the existing rectifier or a new diode must be connected as a discharge diode around the magnet coil. Without that, the inductive voltage spike would soon destroy the switch/relay and even the coil insulation. The existing rectifier provides this function in addition to converting AC to DC.

 

[pc1966]

I'm wondering what it is for, DC injection braking perhaps?

In that case going from 400V delta-connection to 230V Y-connection might not be such a big deal. Going the other way would be!

 

[westward10]

Not sure where the term clicker derives from but I have worked in many of the Northamptonshire shoe factories where shoes are still hand made, John Lobb being an elite brand across the world. Fascinating places still using traditional methods and they all have clicker rooms where the leather is cut and graded. People who work these rooms are known as "clickers".

 

[mike-gr]

one more photo of the rectifier. Italian made!
I took some measurements
The voltage on the primary coil of the transformer is 400v.
The output of the transformer is 45v and when i press the buttons the current is 3Amp.
The magnet receives 40.5v from the rectifier!!! (is the rectifier cause this drop in the voltage?)
Inspecting the whole thing i understand how it's working!
The AC after the tranformer passes through the rectifier with the 2 buttons interfering so that only when I press them the 45v DC goes to the magnet and causes the hydraulic piston works!

 

[Lucien Nunes]

The 40.5V DC that you measured might not be strictly accurate because of the waveform. The rectifier output voltage is DC pulsating at 100Hz, however the current through the magnet is probably fairly smooth DC because of its inductance. When the voltage from the transformer secondary drops too zero on each half-cycle of the AC waveform, the magnet current continues 'flywheeling' through the rectifier.

Selenium rectifiers drop approximately 1-2V per plate under load. Unlike silicon diodes where a single diode junction can be made to withstand >1000V in reverse, each selenium junction can only withstand a few tens of volts. To make a rectifier with higher PIV, multiple plates must be stacked in series, each adding to the voltage drop. Your rectifier appears to have two plates per diode, therefore as two diodes are always in series with the load, a forward drop of 4-6V would be reasonable. Note that there is an extra diode at the bottom not in use.

 

[mike-gr]

So i need to check the electric motor now if it's possible to make it run under single phase or i have to change it with a new one. I will also need to change the transformer with another one for 230/45v.
If i use the same rectifier will that be a problem?

 

[westward10]

Transformer will be a straight swap you just need the correct va, rectification can be left in place.

 

[Lucien Nunes]

Something like this might suit:
200VA 230/400 - 2x24V isolating transformer

 

[mike-gr]

Something like this might suit:
200VA 230/400 - 2x24V isolating transformer

This one have an output of only 24v! The one the machine have is 40v!

 

[DPG]

This one have an output of only 24v! The one the machine have is 40v!

I'm guessing Lucien intends you to connect the secondaries in series.

 

[westward10]

Output is 2×24v and you can normally connect for 24v parallel or 48v series.

 

[Lucien Nunes]

Indeed, and with a +15V tap on the primary, you connect the 245V primary to 230V and the 24+24V secondaries in series give you 45V as per the existing one.