I am looking for SCR power controller (for electric heater) which is profibus connected.

Can I use a VFD for this?
My MCC design calls for the electric power controllers to be inside of the MCC bucket just like the VFD's/Starters. My MCC Vendor doesn't seem to know what a SCR is.

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[email protected]
FAX: 17819986590

 

How many zones of heat are you attempting to control? Siemens offers their Powerhouse module which offers many advantages for multiple zone control.

 

Try looking at Watlow controls.

 

Hello;
No, you cannot use a VFD for SCR power control; you use pulse outputs to set the power level you need through the SCR(on/off, zero-crossing or phase control techniques are widely used).
Have a look at the following Process Heating Magazine. It wiil give you information and contacts.
"http://www.process-heating.com/CDA/...ures/BNP__Features__Item/0,3156,19589,00.html":http://www.process-heating.com/CDA/...ures/BNP__Features__Item/0,3156,19589,00.html

Hope this helps,
Daniel Chartier

 

Why can't he use a VFD to drive a three phase heater? It would be pricey but I see no reason it would not work. Might need line reactors to add some impedance. I'd check with the drive manufacturer in any case.

Remember though that the speed signal to the VFD will result in a proportional voltage change, not power. i.e. - 1/2 the signal would = 1/4 the power to the load. This preumes the VFD works on a constant V/Hz arrangement as most do by default.

Speed Signal Power
100% 100%
75% 56.25%
50% 25%
10% 1%
0% 0%

The output power will be a function of the square of the speed signal (e.g.- @ 50% speed signal power = 0.5*0.5 = 0.25 = 25%).

You should be able to use high school algebra to figure out the equation that will give you the correct speed signal for the desired power.

A less pricey option is to buy something that does what you want directly. Watlow and Chromolox both sell such devices. You can probably buy some local Profibus I/O to control it.

Bob Peterson

 

I need only 4 zones, 4 tanks in the plant have electric heating elements.
S. Landau

 

Have you looked at Chromalox (800) 443-2640? They supply SCR Power Controllers for Heating Control Systems.

Regards,
Rocco F. Dominick
Butech, Inc.
550 South Ellsworth Avenue
Salem, OH 44460
Phone: 330-332-9913 EXT:267
Fax: 330-337-0800
Web: www.butech.com
E-mail: [email protected]
These opinions are my own and are offered on the basis of Caveat Emptor.