400v deep fryer circuit

[SimonTHK]

Hello
So I try to figure out how my fryer power the heating elements.
It is a 400 v 3 phase deep fryer.
It has a mechanical thermostat. All 3 phases run directly through the thermostat. It powers 1 phase at a time with approx 5 degree´s difference.
It seems that no heat comes to the heating elements when 1 phase is powered through the thermostat. It gets hot when 2 phases are closed, and hot faster when 3.
I thought that 1 phase would power 1 heating element. But will this circuit diagram only power the heating elements, when atleast two are connected?
And is it correct that 1 phase closed through the thermostat, wont power any heating element?

I am simply not working enough with this stuff, also I dont really work with AC, mostly just dc

Thanks in advance.

I have attached the PDF manual. Page 14 has the circuit diagram.
Ive just come to the thought, that Ive might connected something wrong. Can I have currebnt running through the diode, if I connect some phases wrong, according to the diagram and "light diode" thingy called "Lamp" P1.

 

[rjenkinsgb]

Where about is the thermostat connected in relation to that diagram? I'd expect a basic thermostat to be wired in series with switch K1, to control contactor Q3.

The elements are wired "delta" style, each between a different pair of phases.

With a three phase thermostat, it appears it should be wired directly in line with the elements, after the safety and latch contactors; eg. inline with the T1/T2/T3 outputs from one contactor.

Or, less good, in the W1/W2/W3 connections, which will work the same, though without the thermostat being totally isolated when the contactors are out.

Switching power between Q1 and the contactors will kill two connections with each wire disconnected & need a minimum of two on for any heat, as you describe.

ps. It may be that the W1/2/3 connections are red as they are intended to be removed and replaced by a thermostat, when used??

 

[JimB]

It seems that no heat comes to the heating elements when 1 phase is powered through the thermostat. It gets hot when 2 phases are closed, and hot faster when 3.

That is correct.

I thought that 1 phase would power 1 heating element.

Not in this case.

The heating elements are wired as :
Element Phases
E1 L1 and L3
E2 L2 and L3
E3 L1 and L2

The elements are wired in a delta configuration, so at least two phases are required for something to get hot.

I thought that 1 phase would power 1 heating element. But will this circuit diagram only power the heating elements, when atleast two are connected?

That would be correct if the elements were wire in a star (wye) configuration, with the star point connected to the neutral.

JimB


PS, it looks like "Jenks" just beat me to the "post button".

 

[Diver300]

The circuit diagram shows each element connected between two phases, so wired in Delta. However there does not appear to be separate control of the individual elements.

On page 14 of the instructions, the circuit diagram has a control device, labelled K1. It turns on the lamp P2 and the coil of contactor Q3, also called "Latch", at terminals A1 and A2. When the coil of a contactor is supplied with power, the contacts of that contactor will close. The contacts of contactor Q3 are labelled T1-L1, T2-L2 and T3-L3. Each one of those contacts supplies power to one of the heating elements.

A contactor operates all of its contacts at the same time, so the circuit diagram is showing all of the elements operating at the same time.