Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 37 replies
  • Subscribers 42 subscribers
  • Views 7273 views
  • Users 0 members are here
Options
You may also be interested in
This discussion is locked.
You cannot post a reply to this discussion. If you have a question start a new discussion

Permissible inrush current single phase

Anthony Dicker

Hi

I have had the misfortune to buy a Lincat Combination Oven for my Hotel.

These normally come in 10kw three phase.  3 x  13amps That's not too bad.

I have the single phase version 1 x 39 amps. Not so good.

It is operating at 1 second on 39 amps

                          0.2 second off  0 amps

                          Cycling continually. for hours.

I have a 40kva single phase supply and can hear the current hammering away incessantly. Lights flickering etc. I asked the manufacture for details of soft starting and duty cycle. They say this is the way they were designed to work. Bang on and Bang off --1 second cycle continually.

I don't have a current (Hee Hee)  Reg book. So I ask is there a reg in place that covers the single phase load criteria.

To add insult to injury-- I have a three phase 65kva standby set.-- I would not put that destructive abuse on one of my 20kva phases, it would shake it apart. So I cannot run it.

Regards -- Tony

Parents
  • 0

    All of these depend on the applied motor (or whatever) being linear with the control signal, on-off is not.

    I think a lot of systems these days achieve an approximation of linear control with hard-on-off switching pulses and then something to smooth the results. Many inverters simply have a fixed d.c. line and switch that on or off at varying speeds/ratios to generate the output - at best a totem pole arrangement between a +ve and -ve d.c. rail - so at that point only two (or three) single voltages can be produced +dc & 0 (or +dc, 0 and -dc). It then relies on smoothing to produce an approximation to the a.c. waveform output expected - occasional narrow pulses yielding a smoothed voltage near to zero, more frequent and/or wider pulses to produce the peaks of the a.c. output. I reckon the oven is working on the same principle - just using thermal inertia rather than inductor or capacitors to do the smoothing. A 1s or 2s switching period is probably quite reasonable from a thermal point of view (if not a single phase supply point of view).

       - Andy.

Reply
  • 0

    All of these depend on the applied motor (or whatever) being linear with the control signal, on-off is not.

    I think a lot of systems these days achieve an approximation of linear control with hard-on-off switching pulses and then something to smooth the results. Many inverters simply have a fixed d.c. line and switch that on or off at varying speeds/ratios to generate the output - at best a totem pole arrangement between a +ve and -ve d.c. rail - so at that point only two (or three) single voltages can be produced +dc & 0 (or +dc, 0 and -dc). It then relies on smoothing to produce an approximation to the a.c. waveform output expected - occasional narrow pulses yielding a smoothed voltage near to zero, more frequent and/or wider pulses to produce the peaks of the a.c. output. I reckon the oven is working on the same principle - just using thermal inertia rather than inductor or capacitors to do the smoothing. A 1s or 2s switching period is probably quite reasonable from a thermal point of view (if not a single phase supply point of view).

       - Andy.

Children
No Data

Join us to get the best from IET EngX.

Joining EngX lets you personalise your experience so you stay up to date on the topics that interest you, plus you’ll be able to make connections who are looking to collaborate, exchange ideas and more.

Join us Not now

Community Rules & Guidelines