Controlling power

Thread Starter

JRV

Joined Oct 27, 2020
3
Is there any AC device that allowes full range control on any circuit independant of load?

I want to be able to use a single controller to increase and decrease the power of any system and without the system affecting the controller. Seems that most controllers need to be bought at specific ratings for every unique system.

Im relatively new to electronics and right now I built a simple AC heated platform controlled via a 4000watt SCR voltage controller. My expectation was that when the controller is at 0 voltage the platform would be off and as I increased the voltage the platform would gradually get hotter but instead the platform almost melted when the controller was set to 0 voltage...

Now I'm adding resistors trying to drop the power of the system so that its atleast at a low temp when the controller is turned to 0 voltage with the hope that I'll have enough range to increase the temperature to where I need it to be.

I guess these controllers that rapidly switch the circuit on and off are not as straight forward as a variable resistor such as a rheostat but getting a variable resistor that handles AC power is too expensive and inefficient so I decided on SCR instead.

Trying to find out about other controllers at the moment and coming across many types like the variable transformer, liquid resistors, pwm's etc and wondering if there exists some sort of digital device that allowes 100% control range on anything from a single low power component to large high power designs
 

Alec_t

Joined Sep 17, 2013
11,739
Is there any AC device that allowes full range control on any circuit independant of load?
No. By way of an absurd example, a controller for a bedside lamp is completely different from one for controlling a power station!
If all you need to control is a range of low-current loads it wouldn't be economically sensible to make/use a controller designed for very high currents.
 

Marley

Joined Apr 4, 2016
369
To control your 4000W heated platform use an SSR (solid state relay) and pulse the power at a varying duty cycle.
The SSR should be driven using a PID temperature controller. This will drive the SSR correctly (if correctly configured). You will also need to embed a temperature sensor in the platform. This could be a thermocouple or a PT100 sensor depending on the operating temperature range.
Typical SSR. Typical temperature controller.
 

Ian0

Joined Aug 7, 2020
739
Is there any AC device that allowes full range control on any circuit independant of load?
The phase-fired triac is about as close as you would get. It will control anything from a filament lamp, to any type of heater, and some types of motor.
It won’t do fluorescent and LED lights, or induction motors, but pretty much anything else.
Having said that, there are much better ways of controlling heaters that don’t generate quite so much interference.
 

LowQCab

Joined Nov 6, 2012
65
If "Your Platform almost melted" it is very possible that it is not well matched to the job description.
How fast does the Temperature need to rise to the Target Temperature ?
You should start out with a Heating Element that, under Full Power,
will attain the desired Temperature in an acceptable Time Frame, preferably in excess of ~1 minute.
You may have a 2000 Watt Element that flies past the Target Temperature within Seconds.
This will create serious challenges with Control that are completely unnecessary.
Are you Heating Air, or directly heating some type of material or liquid ?
Depending upon the amount of Mass, and the Materials used in the construction of your device,
you may be putting a Nitro-Burning Dragster Engine on a Riding Lawn Mower.
Not recommended.

Do you have a single Heating Element, or Multiple Elements ?
Multiple Elements can facilitate different wiring arrangements which can sometimes simplify Power Control.
More simplicity is better, and generally more reliable, and sometimes safer.
Any type of Control that is not switched Full-On, and Full-Off, is going to dissipate tremendous
amounts of HEAT, and require a huge Heat-Sink.

A single High Power Diode, (on a Heat Sink), and 2- Cheap Thermostatic Switches may be all you need.
.
 
Top