Can a VFD do magic with motors

[Guest]

The Magic is in the numbers.

The fabric drying company has probably found the best combination of temperature and dwell time for a maximum production rate. However, they have never had control of the blowers.

I suspect that the blowers not only convey the the hot air but also dry the fabric directly by blowing across the product or moist air displacment. Slowing the blowers at low fire with an on/off controller gives the process a double wammy.

Om the line with the new VFD's, perhaps runnimg the blowers near the the infeed end at 110% and direcly (or inverse) control the dischage or middle blowers could tweak production a few percent.

I understand this was a question about saving electricity. But a production increase does so indirectly. You could be a hero.

 

[fareast]

Hi,
I'm going to go off on a bit of a tangent. I install a lot of large (1.5MW+ gas heat) industrial dryers and toasters , however , the combustion air fans on these burners are so small (.37->.5kW) that it wouldn't ever be worthwhile connsidering the use of VFD's on these motors (We also never bother with airdamper modulation on these burners as the burner plates give us varying air dilution ) . The big savings on our machines are made with the circulation fans and the exhaust fans which use volume control disks and blast gates . So long as the pulley sizes are reasonable (so that the VFD is not running at silly frequencies to get good airflows) then we can increase efficiencies using VFD's without compromise , in fact there is a bonus , as there is no turbulance normally associated with volume control disks (I have seen the air actually reversing in places using disks) .
Like the others replying , I am more than a little surprised that anyone would recommend that a gas burner combustion air fan be fitted with a VFD !? I would thinks that your dryers must be fitted with zone circulation fans , and these could usefully be fitted with VFD's.

 

[shooter]

i have some magnets you can wind around the conductors this will get rid of the chalk in the cable.

How can you save energy with something in between????? it will cost energy as these drives need cooling more than a simple contactor.
Even the motors will heat up more because the voltage is chopped.

and yes everybody knows when slowing it will save energy double.
again an unsatisfied but paying customer of abb.

 

[brarny]

I've just read all the above with interest.

I came across it all by chance looking for info on energy saving etc using VFD's.

The applications I am considering using VFD's on are Combustion air fans and hot air supply fans from both tunnel kilns to my dryer.

Firstly the combustion air fans on the kilns, each kiln has 1 fan supplying combustion air to 5 zones of burners. The fan motors are rated at 37kW 3 phase 415V running direct on-line. These deliver the required flow of air to all my burners each being 'throttled back'(quite considerably) by individual ball valves. The inlet damper (before the fan) is also 'throttled back' on 1 kiln (the other fell to bits and hasn't been replaced).

The fans supply a pressure of about 45"wg at 50C, but as I have mentioned both inlet damper and individual burner air valves are restricted.

My thoughts are;
Either fit smaller/slower motors to the combustion air fans, therefore reducing energy consumption, still maintain flow of air by opening the inlet damper, where still in existance and opening individual valves at the burners.

Or, fit inverters to the existing motors (37kW), slow the fan speed and open up dampers/valves as above.

Obviously I must maintain enough 'head' of pressure to get the air to the furthest burners in the system but I for one think it's possible.

The dryer supply fans are a different concern, I am aproaching these with the view that they will give me more controllability if fitted with VFD's and pressure/flow control loop. These fans are restricted by dampers pre-fan to achieve the require air flow for each rate of throughput of ware. Fitting VFD's should ensure more accurate control of the air flow to the dryers with added energy saving as a bonus. These fans have 11kW motors and shift are in excess of 200C.

As I appear to have fallen upon a group of people with varying experience of VFD's and fan laws etc I though it might help make up my mind and those of the money men who ultimately sanction these projects.

P.S. There are control benefits to be had with the combustion air being controllable when balancing my kilns when I have to create a reducing atmosphere in the kilns. Or at least I thinks so.

Anyway over to the experts. Please please please help!

 

[Rick Densing]

A suggestion- when you have an new question- start a new thread. It make housekeeping easier.

 

[glaverty]

Well since its back

I'm curious as to what the outcome of this was Goody?

 

[jimtech67]

I can do magic with cads


Jim


Could not resist since the thread came back to life

 

[DickDV]

I'm starting a new thread on this entitled "fan drives for brarny"