The same level of current switching, but with a PWM cycle period of a few minutes to kiloseconds, rather  than  every 50 cycles would be perfectly acceptable. The problem is not the simply magnitude of the current step but the fact that it is at a rate that compares to the sensitive region for human flicker sensitivity. There is a reason for the standards I referred to above being worded the way they are !.

Now, this kit does not really comply for connection to UK mains. and as such should never be CE or UKCA marked or placed on the market.

A very nice thing to do would be to run the elements in parallel for fast heat and then in series for maintainence, but that too would require some design competences.

Mike.

No Andy, you have that wrong, a PID controller CANNOT work in that way. I suggest a textbook on control systems design would be a good start. You will find that the system requires a time constant to enable it to be stable, If you work on a 50Hz sample period the control loop requires damping sufficiently that "overshoot" cannot occur, which is one of the symptoms in this case. The integral cannot work if the control is not fine enough, and the proportional part needs to be exactly that, the error must be able to be set without any overshoot. So if 1 cycle of power leads to a small increase in temperature (which it will), the control system must then provide a longer gap to reverse the error, a rough description of the proportional part. The time constant stops the control system oscillating around the set point. This product is simply defective. Working it on 3 phases reduces the current but does nothing else useful. The control needs to be fully linear too, but that is only provided with a suitably high PWM frequenbc, considerably higher than the temperature sample rate (which makes the control quasi-linear).

Hi -I live in a rural area North Wales. It is an 11kv /440v TX supplying three properties but the Board only ran one phase to my property.

I have told LINCAT the catering equip supplier- It is not fit for purpose. for many of its faults and have a case pending against them in the County Court in Wrexham.- Do any of you have the regulation that I can quote on the --Violently Oscillating Current.-- And produce in court, as evidence of  defective design..

  Any Engineer will know the abuse my incomer is experiencing. 50 starts per hour with no ramp up s appalling. I will not even run it on my genset.

Hi Clive Sorry -I have been off this for a few days due to hunting down a gremlin on the hot water controls I have motor valves scattered hither and yon    with a N to E fault.  always a ***.-------I am up on the Horseshoe Pass Llangollen. It is a 3 wire 11kv line and a 50kva TX 440v -240v  serving three properties. The board only ran a single phase 50kva MD line to the place way back.

In the Catering equipment business.     --They Have No Standards As We Know It Jim--------(Kirk)

They ask for a 50 amp breaker and that's about it.-- And in she goes.

No Andy, you have that wrong, a PID controller CANNOT work in that way. I suggest a textbook on control systems design would be a good start.

I'm not sure what your text books tell you, but real world data seems to indicate that's exactly how they can work - e.g. https://docs.rs-online.com/394e/A700000008720058.pdf On others (e.g. https://docs.rs-online.com/9117/A700000008735838.pdf)  choice of power switching rate is influenced by the type of switching device - short (<2s for entirely SSRs, far longer where mechanical relays are used).

   - Andy.

Anthony Dicker said:

I have told LINCAT the catering equip supplier- It is not fit for purpose. for many of its faults and have a case pending against them in the County Court in Wrexham.- Do any of you have the regulation that I can quote on the --Violently Oscillating Current.-- And produce in court, as evidence of  defective design.

Good luck! I suspect that they may try to argue that your supply is inadequate.

Have you asked SP Energy Systems for a quote for 3-phase?  A friend in Mold had a single phase overhead supply upgraded to 3-phase underground for around £8K. he dug the cable trench himself (he has a digger) about 120 metres.

Clive

You need to say that is should have been tested to EN 61000 3 3 .
Unless the makers instructions say otherwise,  a customer should expect it to meet this standard on any normal single phase supply.

If it needs a supply with an unusually low resistance or high current capacity to meet this standard, (which is set in terms of number of permissible voltage drop events per unit time.) then they were remiss in not warning you that a supply of remarkably low impedance is needed, over and above the basic third of an ohm or whatever you might reasonably think was adequate for a 50A load.

EN 61000 3 3 is the spec for flickers that 'CE marked' kit should meet - it is set in terms of a fractional voltage drop events over time so depends on both the load step and the supply resistance and the more violent events are only permitted much less frequently.

If the oven is CE marked, they should have either test results or be able to show by analysis, that it meets this standard, if it is CE marked and no such evidence is available then they are not doing the CE marking properly, but if it is not CE marked then it is illegal to sell it as new equipment.

Mike

CE and UKCA are now identical in this example.

Hi Clive you are at the wrong end of the telescope. I am on a three phase OH line reticulation system 3 consumers. Single phase to my property. BUT why should I pay £1 to upgrade- because the oven people cannot keep the elements inrush and short cycle demand  under control.-- ie I was in West Africa- they were burning out 40hp motors at one per week. I found them stop starting the motors  DOL 50 times per hour. That was   killing the motors. I sorted that -and never had another burn out.