freq drives

[Den Socling]

This is not for the guys who make their own decisions but for those who have bosses who are pressured by the big-kiln-manufacturer salesmen.

Freq drives are usually the biggest waste of money that I can imagine being shoved down the throats of kiln operators. They save a few minutes of dwell time (no air) but, in many cases, they don't do much more.

When wood is wet, air is the vehicle that carries water. When wood is nearly dry, you can save some electrical energy by slowing fans. A few cents if you take the time to do it.

A couple weeks ago, a 50 HP A-B blew up at a customer's kiln. The list price for a replacement was nearly $10,000.00. I replaced it with an ABB for a little over $4000.00. The ABB blew up in my face. I got two ABB reps to start up the third. No problem. They have no idea why the previous drive blew up.

Last Friday at 7:30 AM a customer called. A transformer on a pole blew. It blew up four 50 HP A-B's. Nearly $40,000.00 in junk. I spent Friday afternoon trying to make one working drive from pieces. The kiln operator spent the afternoon installing a new A-B that has been sitting in a box as a spare. The junk I put together blew up when we powered up. The new drive 'smoked' when we powered it up. Four new ABB's for $17,000.00 are on their way,

Today, we are installing a new controller and I ask the operator about two freq drives (A-B's) that SII had on their controllers at the same location. He said they were a pain in the butt and they never varied fan speed.

So I ask, why are you DanG noodleheads blowing all this money on freq drives?

[Jason_WI]

I used to work for Marquip in Madison. They designed their own freq drives for there paper processing machines. They also used AB stuff which was pretty reliable. Ahhh the smell of IGBT's exploding and filling up the room with carcinogenic smoke brings back memories.......

If the transformer on the pole had a meltdown then that was probably the cause for the first drives to smoke. Pretty hard to point fingers at the power company to cover the cost of the drives.

Unless you test each individual board in a freq drive its pretty hard to frankenstein one together and expect it to work. The hall effect sensors need to be indivually calibrated otherwise you will have each phase at a different voltage. Bad things happen then.....

I used to calibrate the boards and then calibrate and test each drive in a simulator. There were wooden canes at each test station so that your burning carcass could be pulled off the test station if you touched 480 V. Not too many people survive joining the 480 club.......

Jason

[Den Socling]

Jason,

You make it sound like such a grand adventure.  :D

One leg of 460 (277 to ground) has brought me to attention a couple times but hasn't had any lasting effect.  ;) I just love it when 'designers' use 277 for safeties.

The 1336 plus has layers of circuit boards. Can they be interghanged? Component level swaps would be a total waste of time, I'm sure.

Den

[old3dogg]

I can't comment on freg drives but I am a survivor of the 480 club.

[Den Socling]

For those who didn't know, a freq drive (pronounced 'freak' drive) is not some weirdo with long hair headin' down the highway. That's what my wife imagines every time I complain about one.  :D

A freq drive is a variable frequency drive that is used to control motor speed. Sometimes, they are just the ticket. If I need to vary auger speed to feed sawdust to a boiler to keep the steam pressure at set point, I use a freq drive. If I need to vary pump speed to keep water level in a tank of trout constant while the amount of water being pumped in varies, I use a freq drive.

So now you know even if you didn't care.  

[Jeff]

Funny you mention trout. The MIDNR has 500,000 18 month old salmon die over the weekend at one of its hatcheries because a pump failed due to an electronic control, the control functions were suppose to trigger an alarm if airation stopped, but the control still thought it was working. This is not a good thing for the salmon fishery.

Hey! I just contributed to this thread that I know nothing about. ;)

[Den Socling]

hey I didn't build that one.  ;)