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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

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    Whilst the data sheet looks simple Andy, there is no mention of the required time constants to make this work properly, in fact it is pretty much what is in the product mentioned above. PID control, think of a servo system to control a gun turret, requires that both fast response and great accuracy are available. Clearly full on or full off cannot work. The integral factor for example, integrates a tiny position error over time and then produces a very small control signal making a tiny correction to the position so that the integral error is zero. Similarly the differential part decelerates the movement as the position error gets smaller, preventing overshoot due to inertia, and the proportional part makes a reasonable guess at the movement speed needed with the starting error size. All of these depend on the applied motor (or whatever) being linear with the control signal, on-off is not.

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    Whilst the data sheet looks simple Andy, there is no mention of the required time constants to make this work properly, in fact it is pretty much what is in the product mentioned above. PID control, think of a servo system to control a gun turret, requires that both fast response and great accuracy are available. Clearly full on or full off cannot work. The integral factor for example, integrates a tiny position error over time and then produces a very small control signal making a tiny correction to the position so that the integral error is zero. Similarly the differential part decelerates the movement as the position error gets smaller, preventing overshoot due to inertia, and the proportional part makes a reasonable guess at the movement speed needed with the starting error size. All of these depend on the applied motor (or whatever) being linear with the control signal, on-off is not.

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