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VFD Questions
- Thread starter Rapomay
- Start date
I have 4 producers but they are soft start. That may be a more viable option. Do you plan on using a lower rpm on lower washes?
JimmyJaffa
Member
Most soft starts are good for 6 to 10 starts per hour. After a year or so, they start failing. VFD are robust and really save the motors, air gates combined with VFD are the best for energy savings and motor longevity.
Another advantage to have VFD's is you can run the motors below 60hz and get an equally dry car. We have 11 15 hp blowers and all of them are run off VFD's at 53 hz. Also, when purchasing VFD's, purchase individual units for each dryer versus multiple dryers on a single VFD. It is cheaper and allows you to lose only 1 blower if a vfd goes down.
I sell vfds and have them only because the utility company paid for them via rebates. If you have a tunnel where you can ramp up and down between cars they would be an advantage. For an iba there's very little to no advantage. vfd is simply a speed control. There's a common misperception that the utility charges for the surge to start the motor. No utility I am familiar with is any less than a 15 minute demand charge. (max AVERAGE use for 15 minutes) You may even increase your average because it will take longer to ramp up on vfds. It is probably slightly easier on the motors because they won't see amps that are as high as cross line starting but if you have a vfd there are pulses that are 600 volts plus so on an old motor the vfd can shorten it's life.
Blower
Currently the blowers start for each car then turn off. On busy days they may only be off for a couple of seconds. We have thought about leaving them on all day but I am worried that my employee towel driers may not be paying enough attention and two cars may hit or worse.
Currently the blowers start for each car then turn off. On busy days they may only be off for a couple of seconds. We have thought about leaving them on all day but I am worried that my employee towel driers may not be paying enough attention and two cars may hit or worse.
If you figure what they cost to run at full load amps on the motor nameplate x the service factor that would be at full speed. Ramping them down to 2/3 speed would be 1/3 the power consumption. So you are not going to use less power than turning them off and if they are on you won't save anything if you run them at full speed. You could get quicker ramp to full speed if you set them to slow down between cars but you are still using 1/3 of the power and you use 0 while stopped. It would be easier on your motors than starting across the line so many times repeatedly.
That's a good point. Typically you wold install larger contactors to compensate for short cycle starting. On the vfd's they should last 10 plus years and they don't care how much you start and stop as long as you don't start so fast you have an inrush that exceeds the rating of the vfd.
