22 minutes ago, BritishRacingGreen said:

Thanks, i have notice some areas which is 4x4 territory.  What wattage solder iron you reckon is a good fit.? I want to complement my existing 60w one with somethin beafier. 

Personally I'm partial to the Metcal or Thermaltronics stuff, but that's probably not very good advice for this sort of work (Perhaps the GT120 is a good choice, but it's a bit overpriced for this IMHO). Also note that wattage does not mean much if it can't efficiently transfer energy to the joint, this is where Metcal/Thermaltronics really shine, in many cases you can do the same work with half the power rating just because of the way it works.

Perhaps something like this, but with genuine JBC cartridges?

 

Edited November 6, 20223 yr by P1000

My Hakko FX-888D is rated at 70W; with the 5 mm tip, it does well even in well heat-sunk areas. Beware of cheap imitations.

I have to admit though that I also have a "big bertha" from a hardware store. It's a no-name that isn't even temperature controlled.

Since my last post , I had been involved in creating the schematic page for the dc-ac igbt and buck igbt driver section.  In the process I also updated the power chain schematic. The two schematics below refers:

 

First the update power chain :

 

and the igbt driver section schematic :

 

I struggled initially to understand the 3 isolated power supply feeds . So I added a little context diagram in the bottom left hand of the page. An igbt drive signal must be referenced to its associated emitter .  So from the power chain drawing and the context diagram , one will see that we need  three separate isolated supplies ,one each referenced to INV L  , INV N and BUS - .  The half wave rectified dc output of each  secondary winding  has a RMS value of about 20.5 V . This feeds a 5v6 zener diode via a 18k resistor . In practice there is about 5.3V across the 5v6 zener and 14.8v across the resistor , and of course there are filter capacitors in order to smooth the two voltages . The 18v zener has no function other than clamping overvoltage . If you take the top power supply as example ,  you'll notice that INV L is connected onto the midpoint of the zeners . Now because INV L is the emitter connection for QB2 transistor , the gate voltage can be set to either 14.8V or -5.3V , which is exactly a good turn on and turn off voltage level for the gate.

It must be noted that in contrast to the DC-DC converter on the battery side , the DC-AC converter and BUCK converter are under processor control. The DSP therefore will produce appropriate PWM  signals for the IGBT transistors .This is of course done by a driver interface  IC eg U1.  This ic differ between MAX7.2 and 5KW models , but the basic function remains the same. Interesting to note is this one is not an opto-coupler , but an eDiode (emulated diode , see datasheet) . So light is actually not used .

The processor drive electronics confused me somewhat because of its complexity. I understand the circuit must be fail-safe but I  still don't get the rationale behind this one. Basically R180,R179 and R170 will bias the driver diode into on state . But transistor Q3 is also biased to on , and so will shunt enough diode current away , so the drive diode is off. The voltage across pin 1 and pin3 is 0.1V , the spec requires anything lower than 0.8V . Otherwise with the transistor off, the forward current is about 10mA which switches the ic on (about 2.1V across the diode). The  control pin CN11-1 is active low , so when the DSP wants to switch the IGBT on , then it pulls CN11-1 low , which lowers Q3 bias voltage, shunting less current away from the diode . When on , the pin 6 voltage (14.8v) is routed to the gate output , when off pin 4 (-5.3v)  voltage is routed to gate. 

I initially thought that because of the low resistances of R180,R179 and R170 across the 12V rail , that the faulty high 12V rail  voltage  would probably have  destroyed the driver. But it didn't , not one of them five circuits . The transistor probably have a high enough VCE rating , so it probably saved my but. So really no further damage experienced here except of course the driver transformer , which I rewound.

To test the  circuit , I checked the gate voltage on all igbt's while manually switching the control pins by shorting them. They all passed this DC characteristic test quite nicely.

But I soon discovered that I also need to perform AC characteristic tests , by applying suitable narrow PWM pulses on the pins , and checking the results on the gate pins. This I haven't done yet , because I realized that I will inevitably have to  introduce a controller that can help me out here . So the rest of spare time this week i am going to look at Raspberry Pi Pico and introduce some software control code to drive these signals. In the spirit of this being an open source hardware thread , I will also make the software available to whoever might be interested. This controller will also help me with the relay testing , the bus soft start and other sundry tests.  In the long term I have also a plan to introduce a rudimentary oscilloscope function with small display , in order to empower someone to check signal quality where an expensive scope is not available.

Apart from DC and AC characteristic tests , I will probably also need to verify that I have good isolation between the three sections , and that breakdown will not occur when I start switching the power chain.  How this can be accomplish I must still learn , because low voltage resistance tests will most probably be  not good enough.

I have spent a lot of time here , because the IGBT transistors are particularly expensive , and one would like to leave very little to the imagination when replacing these transistors.

i will come back to do the AC tests when i have done  the software , and bread boarded a rpi pico.

In the meanwhile , I am anxious to move onto the bus soft start section , which intrigues me to no ends . 

 

 

Chapter 4 : Bus Soft Start Section (or not so soft after all)

The idea behind the Bus Soft  Start (BSS) is to allow the processor to check whether there is a short circuit on the dc bus (bus+,bus-) during startup. To accomplish this the DSP triggers  a high voltage power supply connected to the bus to start charger the bus capacitors. This power supply is of course relatively weak , and may take some time to reach the bus terminal voltage so desired. If the terminal voltage is not reached within a predefined window of a number of seconds , the DSP aborts and raises fault code 09 (Bus Soft Start Fail) .

The schematic of the BSS PSU is shown below :

It is really a standard SMPS design built around the UC3845 as with the Main SPS power supply. The transformer TX2 obviously has a huge voltage gain by means of appropriate turn ratio. The primary is switched by SPS+ (48 - 61 volts dc) .

It can be seen that there are no voltage feedback U16 to regulate . The PWN duty cycle is typically zero due to the fact that FB pin 2 sits at 5v reference voltage . If this pin is pulled low then the duty cycle will increase and when it reaches 0V , the duty cycle is at its maximum limit 50%. So the DSP can start the PSU by pulling FB low via opto-coupler interface U17.   The high voltage bus output will then produced.

The chip is fed via the 15V supply from the main SPS. I had to initially carefully cut a pcb track to isolate this circuit from the SPS as it had a short circuit. So I had to start looking for this short circuit before connecting power to it again. My initial guess was zener diode ZD9 as it is across the 15V power rail. I was correct , removal of ZD1 removed our short circuit . Obviously during the high voltage fault this zener clamped and went short circuit , heroicially saving the other components during the last moments before it died completely. That why I believe in voltage protection , and fortunately zeners appears to go short circuit , unless of course the input current gets too high . When this clamping occurred the , R66 and R67 on the TX9 secondary winding  (5&6) of the main SPS PSU also blew open circuit so it acted as fuse. The zener ZD1 had a short resistance of about 70 ohms . I replaced this zener not knowing its value but I choosed 18V 1W version. I also replaced the electrolytic capacitor C10.

My hopes were high that the rest of the circuitry was protected , and indeed when I switched on U16 VREF output showed 5V reference voltage. All it need now was for me to enable the chip by pulling the DSP control pin CN11-4 low to GND. I did just that for a small number of seconds , after which the main motherboard  shocked the cr@p  out of me🙄 . I start shaking , I am sure you would have been able to take a group photo of me🥴🥴🥴🥴. And this is my first rendezvous with high voltage pcbs . obviously have a lot to learn about safety measures when bringing up the bus circuits.  Please take note and don't fail like me. !!!!!!!!!!

When I got to my senses I measured the bus voltage and it was sitting at 315V . So the psu circuit works , again I must use the raspberry pico to pulse the input in order to controller a slower charge rate , I think . What I dearly realized is when the bus capacitors charge up , the supply is not so soft anymore , as these caps are not small. We can maybe still fry a mosfet or igbt with this energy , i hope not .  Also , the discharge path resistance is very high , so it takes forver to discharge. Take note of this when you switch off.

@Coulomb, incidentally ZD9 is not shown on maxo's schematic , and neither R66/67 as you already know .  Also there is a portion of maxo's schematic I cannot relate to what function it serves , neither can I find any of the components on the MAX motherboard. Its the circuit in the snippet below build around U6. It makes reference to bus soft start .

 

EDIT : Also , ZD9 is a peculiar glass tube device , leadless. Is there any significance in this  I need to read into ?

 

 

Edited November 9, 20223 yr by BritishRacingGreen
Extra info

2 hours ago, BritishRacingGreen said:

The idea behind the Bus Soft  Start (BSS) is to allow the processor to check whether there is a short circuit on the dc bus (bus+,bus-) during startup.

The other idea is to pre-charge the large bus capacitors, so that various circuits don't attempt to charge them from zero volts with excessive current. This is kinder on the capacitors, and also on those circuits. For example, the DC-DC converter.

2 hours ago, BritishRacingGreen said:

incidentally ZD9 is not shown on maxo's schematic , and neither R66/67 as you already know . 

R66 and R67 are there now, in Rev 10c. ZD9 appears elsewhere in the circuit, so it appears that this voltage clamping ZD9 is new since 2013.

2 hours ago, BritishRacingGreen said:

Also there is a portion of maxo's schematic I cannot relate to what function it serves

It seems to be sensing the presence of voltage from the utility power supply, which disappeared soon after this model. It re-appeared on other models, but may have different parts designators by now. Do you have U15 or TX6?

12 hours ago, Coulomb said:

The other idea is to pre-charge the large bus capacitors, so that various circuits don't attempt to charge them from zero volts with excessive current. This is kinder on the capacitors, and also on those circuits. For example, the DC-DC converter.

R66 and R67 are there now, in Rev 10c. ZD9 appears elsewhere in the circuit, so it appears that this voltage clamping ZD9 is new since 2013.

It seems to be sensing the presence of voltage from the utility power supply, which disappeared soon after this model. It re-appeared on other models, but may have different parts designators by now. Do you have U15 or TX6?

@Coulomb   No, i can find no trace of any TX6 or U15 on the main board. 

looking at the main board at sections i have not covered yet, i only see the following : 

1  AC circuits including relays and relay driver circuits, EMI filters, movs etc. 

2 fan control and sense

3 current sensors, various

4 voltage divider chains

5  a circuit involving SMD inductors L7 and L8 with some silicon associated. searched for L7/8 on your schematics but found none. 

Edited November 10, 20223 yr by BritishRacingGreen

Chapter 5 : Beginning of the End 

I am definitely not out of the woods yet , not sure yet if the fan controls and relay switching logic , control board and display will work , but I decided last night to introduce the control board and display. I have no way of verifying the operation of the control board , other than to make sure that there i no bad resistance between rail supply inputs etc.

So I inserted the control board and realized early that one can actually misalign when docking it to the main board , which I reckon could cause havoc , and undo all our hard work. I wired up the bare minimum , including the display .

Switch on , and after the usual startup timer timed out , it gave me Warning 01 , fortunately that is fan locked , so i plugged in the 3 fans . The machine then started up  without any further warning or error . obviously the battery icon flashing as well because I have not connected battery or grid to the power chain.

I was satisfied with the progress and decided to  add battery power  in the early morning , which will be an indicator whether all my hard work was worth the while.

No PV  modules added as that is the very last thing i will do in the final analysis . PV1 metrics does show up on the display though , but that is hogwash. I have seen it before on other machines as well when pv mppt module removed .

Today I decided to take the big step to add current limited DC power  to the battery port and bring up the power chain. A bit nervous though .I have two 30V variable supplies I cascaded to set to aggregate of 51V.

Here is me pre-charging the MAX battery input with suitable resistor.

 

and here is me going firing  51V DC , attacking the MAX full-on , no more 'Mr Nice Guy' :

 

The MAX submitted  immediately , produced about 380V on the BUS , opened its front porch with a beautiful sine wave 228VAC .  I also checked the IGBT gate drives and saw the magic in action . One half bridge had a continuously changing PWM to produce sine , wheras the other part of the half-bridge was constant at 50% duty cycle @50HZ.

Have I won the war ? not yet , but many battles yes , still has lots of work lying ahead . So the journey continues ....

 

Hi @Coulomb, this unidentified circuit on the MAX puzzles me . I have started to trace and noted that near R181 is a 8 pin DIP  precision op-amp type OP07CP .  The negative rail of the OP07 is fed via -12V rail  filtered by L8  , while the positive rail is fed by +12V rail filtered by L7 . 

Still in the dark where the INV and NON-INV signals come from and where the op-amp output is routed  to .

Can you relate to this circuit ?

 

 

7 hours ago, BritishRacingGreen said:

Can you relate to this circuit ?

Apparently in some models the LEM Hall effect current transducer is replaced by a shunt and precision op-amp. Small discussion here. 

14 hours ago, Coulomb said:

Apparently in some models the LEM Hall effect current transducer is replaced by a shunt and precision op-amp. Small discussion here. 

ok thanks I had a look at the forum discussion. However I cannot trace any connections between the OP07 amplifier and that of the LEM or the current transformer . The LEM on the MAX is of type shown below :

On the MAX the +12V and -12V are routed to the +15V and -15V inputs. The output pin 4 is directly routed to one of the control board connectors. equally , the current transformer HCT1 i directly routed to the control board , with only suitable burden resistors connected on the main board.

I will step down from this for the time being , but will replace the OP07 as well , as the fulty rail voltages would have urely destroyed this device , as both =12V and -12V are connected to this device.

 

 

 

Below is my first version of the MAX AC routing and relay control interface.  Maxo's schematics proved a little challenging for me so I had to trace the circuits. Difficult , because the inductors and current sensors hs near zero ohm readings. Also there are less components on the MAX than shown in Maxo's schematic.

Below is the schematic :

Major differences between Maxo's and mine :

1 .On the MAX the relay contacts are double cut as shown.

2 On the MAX  both the N/O and N/C contacts are wired to the bonding relay in order to entertin earth bonding.

3. On the MAX there is only 3 relays as shown , and only 3 relay interfaces

4. on the EMI filter there is only 1 capacitor loaded 

If anyone can understand the reason for Q34 transistor , please share , because I have no clue. Also the relay drives with pnp is unusual . But I have also traced these circuits and mostly correlates with Maxo's schematic .

Two zeners on the relay interface had been found blown because of the big bang fault. Still need to replace them . I have removed them though on an earlier occastion when i switched on the machine.

@Coulomb While tracing I found the system GND (the reference of +12V,-12V,+5V) to be hard connected to INV N (neutral) . Actually I assume its actually hard connected to Earth , due to the INV N being anchored to earth via the bond relay resting contact. I confirmed this on my other reference board. 

Also , members must note that when mounting the main board back onto the chassis that ALL screws MUST be fitted. The reason is some sections of earth on the board are not interconnected but instead rely on the chassis connections. This is of particular interest to the earth bonding relay , as its earth connection depends on the screw just next to the relay.

 

 

 

22 minutes ago, BritishRacingGreen said:

Also , members must note that when mounting the main board back onto the chassis that ALL screws MUST be fitted. The reason is some sections of earth on the board are not interconnected but instead rely on the chassis connections. This is of particular interest to the earth bonding relay , as its earth connection depends on the screw just next to the relay.

This is especially important & from the very limited reassembly of these machines I have done, I have seen reference to this when they indicate an Earth symbol on the actual boards to make repair technicians aware of this. 

Very interesting & note worthy indeed 🤠 Board & screw contact to the chassis forms part of the earth bonding relay. 

11 hours ago, BritishRacingGreen said:

However I cannot trace any connections between the OP07 amplifier and that of the LEM or the current transformer .

Interesting. My understanding is that the 5 kVA inverter with the OP07 op-amp didn't have an LEM at all.

Maybe this is for battery current measurement?

Edit: Or grid current measurement? I don't see the LEM in this circuit, as I would expect.

Edit 2: Ah, the LEM might be just before L4, near the INV L label.

Edited November 13, 20223 yr by Coulomb

10 hours ago, BritishRacingGreen said:

3. On the MAX there is only 3 relays as shown , and only 3 relay interfaces

That seems to be standard since about 2014 or 2015. From memory, the inverter relay is removed. Indeed, you show nothing connected to CN11 pin 11, which I know to be "/INV_RLY" (leading slash indicating active low). So the one you have labelled as Inverter relay is better called the Load or Output relay. The one you have labelled Earth Bond relay happens at the same time as the Grid relay, so it's probably better called the Grid N relay (with the Grid relay called the Grid L relay).

[ Edit: My suggested relay names would agree better with this old block diagram:

]

 

10 hours ago, BritishRacingGreen said:

If anyone can understand the reason for Q34 transistor , please share , because I have no clue.

It's a fairly standard temporary voltage doubler circuit, so that the relay initially sees nearly 24 V to pull it in, then sees less voltage to keep in pulled in. I'm surprised that the other relays don't have the same.

10 hours ago, BritishRacingGreen said:

While tracing I found the system GND (the reference of +12V,-12V,+5V) to be hard connected to INV N (neutral) . Actually I assume its actually hard connected to Earth , due to the INV N being anchored to earth via the bond relay resting contact. I confirmed this on my other reference board. 

Yes. I believe that you should remove the connection from earth to GND near the EARTH label. BTW, the nearby relay contacts should probably be RLY1B, not RLY3B.

Edited November 13, 20223 yr by Coulomb

On 2022/10/29 at 9:58 AM, Coulomb said:

Yes, exactly. It's easier to think of in DC terms, so pretend that the grid is a battery, and the inverter is able to produce a voltage a little lower than the grid-battery, so power flows into the inverter. The electrons just roll down hill, as it were, simplifying horribly. If the inverter creates a voltage just higher than the grid-battery, power flows out if the inverter.

In the AC case, there is phase as well as amplitude, and of course things are cycling 50 times per second. For some people, it helps to think of phasor diagrams, where there are vectors representing the instantaneous phase and amplitude of the inverter and grid, and these phasors are rotating at 3000 rpm. But you use a strobe light to freeze them, and you can see that there is a small gap at close to 90° between the two vectors, and that gap represents the voltage across the inductor. That voltage will be positive or negative depending on the relative phase of the two vectors, which the DSP has control over, as long as the grid is reasonably stable, and it usually is. Even in South Africa 😃. Now the voltage and current in the inductor are 90° apart, so that means that the current is roughly in phase with the two other vectors. So you get high power factor. Though if you change the amplitude of the inverter's vector, that pushes the inductor's voltage away from a right angle, so you can affect the power factor (importing or exporting VARs) by changing the amplitude. It's all quite tidy mathematically.

I am revisiting this post of yours as this has made me realise, that i can only understand  your explanation by brushing up again on ac theory and vectors . Wihich i am doing again after nearly 40 years, spending a little period before bed time every night. (i still have the Hughes book on AC theory, its still available 10 th edition). 

In the process i am also brushing up on my LTSpice simulator. Very handy to construct basic RLC scenarios for education.

Do you think its possible to eventually demonstrate gridtie  basics operation with the aid of Spice models.? 

 

7 hours ago, BritishRacingGreen said:

Do you think its possible to eventually demonstrate gridtie  basics operation with the aid of Spice models.? 

Yes, I think so. You can represent the grid and inverter output as ideal AC sources that you can adjust the phase and amplitude of.

10 hours ago, Coulomb said:

That seems to be standard since about 2014 or 2015. From memory, the inverter relay is removed. Indeed, you show nothing connected to CN11 pin 11, which I know to be "/INV_RLY" (leading slash indicating active low). So the one you have labelled as Inverter relay is better called the Load or Output relay. The one you have labelled Earth Bond relay happens at the same time as the Grid relay, so it's probably better called the Grid N relay (with the Grid relay called the Grid L relay).

[ Edit: My suggested relay names would agree better with this old block diagram:

]

 

It's a fairly standard temporary voltage doubler circuit, so that the relay initially sees nearly 24 V to pull it in, then sees less voltage to keep in pulled in. I'm surprised that the other relays don't have the same.

Yes. I believe that you should remove the connection from earth to GND near the EARTH label. BTW, the nearby relay contacts should probably be RLY1B, not RLY3B.

Thank you  for explanation , I will align my schematics and context with your terminology , so I can refer in the future without confusion .

The OPO7 circuit resemble something like this. The two qurztion marks are where there are two thru-holes and but cannot find where it is routed to. Same with the pin 6 output. It doesnt go to control board.

13 minutes ago, BritishRacingGreen said:

I will align my schematics and context with your terminology

I meant to say that it's not just my terminology; presumably Voltronic will use the same terminology in service manuals, some of which we may not have seen yet. It would be best not to have incompatibilities between the two, it would be so confusing.

5 minutes ago, BritishRacingGreen said:

The OPO7 circuit resemble something like this. The two question marks are where there are two thru-holes and but cannot find where it is routed to.

If I'm not mistaken, that's a voltage gain of 66.67 (the 75 and 150 ohm resistors are effectively in series). So 0-3 V at the output would be 0-45 mV; 50 mV is a common value for a current shunt.

But you'd think that a current shunt would be pretty obvious, especially one that can handle 16 kW briefly (say 16 000 W / 220 V = 72.7 A). Surely if they started implementing a current shunt and didn't finish it, they wouldn't bother populating these parts.

Very strange.

8 minutes ago, Coulomb said:

If I'm not mistaken, that's a voltage gain of 66.67 (the 75 and 150 ohm resistors are effectively in series). So 0-3 V at the output would be 0-45 mV; 50 mV is a common value for a current shunt.

But you'd think that a current shunt would be pretty obvious, especially one that can handle 16 kW briefly (say 16 000 W / 220 V = 72.7 A). Surely if they started implementing a current shunt and didn't finish it, they wouldn't bother populating these parts.

Very strange.

Thanks , I also reckoned that should be from something like a shunt .

I am currently in the favorable stage where I am busy sweeping the whole board to find components and/or sections I have not documented yet . I have already discovered the LEM and fan control as outstanding  , as well as the input sources to the main system psu (mains , batt,pv) .         I do hope there are no 'hidden' smt on the component side , but so far Voltronics has put all there SMT on the 'solder side'  , as far as i am aware.

This has also prompted me to draw a detailed system block diagram at some stage .  

Here is a question I have for you in terms of analogue instrumented  measurement equipment. . So if we want to measure  say 230VAC  , then we can introduce transformer or even opto-coupled  interfaces to level down the measurement to DSP ADC levels. However I see that chains of high resistance are typically routed to the control board , where it appears that TL074 amps are used as differential amplifier  with these chains as inputs , configured with suitable gain to represent say a 3v3 swing for ADC ,. While I understand that these resistances are very high  and the chains have been constructed to handle flashover etc, my understanding is that these methods remains non-isolated. .So my question is :  is it acceptable to have analogue front-ends like these  in microcontroller systems where there are user interaction , say a  LCD graphical display with switches and buttons (on the same system supply) ? Or must user interfaces be electrically  abstracted from this by means of electrical  isolation  ? The reason why i am asking this , is because i am working my way towards a repair-level microcontroller with LCD and old school pots and switches to help me excite and test  functionality on the machine while the control board is out-of-circuit. 

9 hours ago, BritishRacingGreen said:

So my question is :  is it acceptable to have analogue front-ends like these  in microcontroller systems where there are user interaction , say a  LCD graphical display with switches and buttons (on the same system supply) ?

Good question, and I don't know the answer.

14 hours ago, BritishRacingGreen said:

So my question is :  is it acceptable to have analogue front-ends like these  in microcontroller systems where there are user interaction , say a  LCD graphical display with switches and buttons (on the same system supply) ?

Yes, as long as the interface is electrically isolated from the user. It's exactly the same situation as a switch in an appliance.

16 minutes ago, P1000 said:

Yes, as long as the interface is electrically isolated from the user. It's exactly the same situation as a switch in an appliance.

Excellent point, of course the user interface itself can provide further  isolation,  quality toggle switches and pots with non mettalic knobs. 

I am having a little break/timeout for a day or so as far as the MAX repair is concerned . So I am also trying to understand the techniques and math behind grid-tie technology . In my search I came upon a very neat video in very neat English audio . This video confirms what Coulomb has stated elsewhere in this thread that the direction and magnitude of power flow is mainly controlled to the inverter's voltage phase angle in relation to the grid voltage . So real power charge or discharge is actually achieved by manipulation of reactive power . I think the theory behind this is actually magic.  Also starting at about 4:24 in the video the author explains a Spice simulation model which illustrates the theory . The components of the model is rather straight forward . I will want to try this on LTSpice , and will share it  should it prove worthwhile.

 

 

Edited November 14, 20223 yr by BritishRacingGreen
Correction