The VFD's we use are Powtran and they have excellent documentation and factory support. There would be hundreds in service driving CV's in Oz and I know of one failure and it was running continuously 8 hours a day in a commercial workshop.
The VFD's we use are Powtran and they have excellent documentation and factory support. There would be hundreds in service driving CV's in Oz and I know of one failure and it was running continuously 8 hours a day in a commercial workshop.
Last edited by Chris Parks; 05-18-2018 at 8:35 AM.
Chris
Everything I like is either illegal, immoral or fattening
Several past threads discussed this. Here's one from 2011: https://sawmillcreek.org/showthread....art-on-Cyclone
JKJ
2011! Time flies when you are having fun. My comments in that thread were written before I had become the CV distributor for Australia and my cyclone was using a Huanyang VFD. Shortly after I began selling CV's in Australia Huanyang kindly discontinued the model we were using and fortunately I was forced to find & use the Powtran which was a very good move as it had so many advantages, was a far better specced unit and way better made. I can't speak too highly of the company to tell the truth.
Chris
Everything I like is either illegal, immoral or fattening
Hi John, a lot of the heat is also in the rotor where the aluminum bars are located. This is the winding in the rotor and it can be damaged by excessive slip (overload or frequent starting).Originally Posted by John K Jordan;.[/I
Regards, Rod.
I'm sure there is a lot of heat in the rotor, but is it higher than in the stator. When studying this once I remember that for induction motors the hottest place in the motor was the stator coils, perhaps because they are directly powered to produce the fields that induce current in the rotor coils. Baldor indicates the hottest place in a motor is the stator slots. And everyone agrees that heat in the motor is a primary killer since it causes the insulation to break down and short the coils.
Regardless, the temperature inside will be hotter than the outside. I read one source that said a large TEFC motor might be 25 deg C cooler on the outside of the case than in the windings! (They didn't say how large the motor was.)
JKJ
I suppose heat on the rotor is of less concern, but it's possible to have a wound-rotor induction motor (instead of a squirrel cage), and the failure of insulation, there, could kill the motor. Even in a squirrel cage, insulation between the laminations could fail.
What's interesting, though, is to consider how heat gets out of the rotor. Take a TEFC for an extreme example: while the stator coils are in contact with the outside case (which is cooled by a fan), the only ways to get heat out of the rotor are via radiation TO the stator coils, or conduction out the shaft or to the stator coils via the air gap. Obviously, the rotor could be very hot without the case being hot, at all.
I guess I might fall into the person with anecdotal experience of the user mentioned above but only with Leeson three phase motors...do they behave differently to single phase? I have no idea.
I sold many three phase Leesons on Clearvues and to this day I know of no failure with any of them using a VFD and with no restrictions specified on the number of starts per hour. Certainly my personal CV is started whenever I want it to be running with no evident problems. I can't comment further than that and I would be interested if the start per hour figure is different single phase to three phase.
Chris
Everything I like is either illegal, immoral or fattening
I think the VFD would be a great addition - I suspect the gentle start would be a big help to motor life. I don't know anyone here using a VFD on a cyclone. Leeson or one of the other respected motor companies (Baldor?) might have starting guidlines for both 3 and single phase power you could compare. Or ask them.
I also have a 5hp single phase motor on my air compressor. When I'm using air tools that cause it to cycle a lot I worry about the number of starts per hour. I didn't find any recommendations in the manual.
I also wonder about the usually unmentioned factor in motor life - the wiring size and length of run. If not careful it would be easy to size wiring too small or right on the edge such that the voltage drop would cause increased current draw and higher temperatures leading to higher resistance in the wiring and higher current draw in the motor, etc, etc. I ran #6 wire about 40' to the air compressor/cyclone closet in my shop to make sure of this. I know a lot of motors have failed from trying to pull too many amps through wire too small. I suspect three-phase would help with that problem as well.
I think the VFD is a great addition to a cyclone and there is nothing stopping anyone from ordering with a three phase motor. It must be far kinder to the motor to ramp it up to speed over a few seconds than hit it hard with an on/off switch. When the US govt legislation caused Leeson to change the original motor supplied to Clearvue we sourced a motor from Australia which has been equally as reliable.
Chris
Everything I like is either illegal, immoral or fattening
For what it's worth industrial and utility fans used in thermal power plants ie boiler forced draft (think combustion air supply) and induced draft (think combustion products exhaust ) fans with motor HPs in the hundreds or even thousands are always started with the dampers fully closed to protect the motor from burning out. This is from my experience as a boiler engineer (retired).