Craigslist deals

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isac777
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Craigslist deals

Post by isac777 » Wed Aug 06, 2014 10:42 pm

I'm what they call a "sparky" as well and hooked up a drive the other day that somewhat blew my mind. It was a single phase plug to a drive 120v that output 208 3phase to control this PD pump. Here all along i thought u need a phase adder and such to go from single phase to 3 phase when i reality it was just a $250 drive from grainger. I will def keep this in mind when i need to control a small 3 phase motor. This one was like 3/4 hp

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Desert Diver
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Re: Craigslist deals

Post by Desert Diver » Thu Jul 24, 2014 9:20 pm

Jeff Pack wrote:Only downside, is when you slow'm down too much , heat builds up in the motor, and the VFD will shut it down.


Jeff, I never noticed this thread had continued till right now. The reason the VFD shuts down when you slow a motor too quickly is because when you reduce the frequency the motor is generating back onto the DC buss of the VFD and most VFD's have no way to put that power back to the incoming line. When the DC bus voltage goes too high the VFD shuts down to protect itself. Most VFD's have a place to hook up resistors so the waste power from slowing down the motor can be shunted to the resistor bank. I have this setup on my small lathe, and have put them on sawmill VFD's. I can set the deceleration time on my small lathe to 1/2 second and it stops like you hit it in the head. In one of the sawmill applications a log running at speed in the same direction as the chipping heads and saws cutting on it could be braked rapidly any time the heads or saws started to go overcurrent. I put overcurrent sensors to protect the resistor banks but have never tripped them and the motors seem to deal with it very well.

Brian

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Mateo1147
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Re: Craigslist deals

Post by Mateo1147 » Fri Jul 04, 2014 9:57 am

Jeff Pack wrote:Only downside, is when you slow'm down too much , heat builds up in the motor, and the VFD will shut it down.

Unless you have a temp sensor input from the motor to the VFD it has no way of protecting the motor from slow speed overheating. That's up to the person setting up the parameters to put in the minimum Hz to keep enough air moving over the motor for cooling. Most of the drives I install have both 0-10V and 4-20ma inputs available to control the output Hz and start and stop functions. They really are the coolest motor control devices since SCR softstarts came out, especially for high h.p. motors. I'm on a project right now that has a 200 h.p., 480V vacume pump motor to be added. It used to take two sections of large gear to start and run a motor this size. Now it is handeled from a wall mounted can 36"x48"! I'm sure desert diver has hooked up many part winding or delta start, wye run motor starters. They were huge depending on the size of the motor.
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Jeff Pack
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Re: Craigslist deals

Post by Jeff Pack » Thu Jul 03, 2014 12:47 pm

Only downside, is when you slow'm down too much , heat builds up in the motor, and the VFD will shut it down.
=============================================

- I got a good squirt in my mouth
- I would imagine that there would be a large amount of involuntary gagging
- I don't know about you but I'm not into swallowing it

CCR discussion on Caustic Cocktails.

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Re: Craigslist deals

Post by Desert Diver » Thu Jul 03, 2014 7:23 am

Jeff Pack wrote:VFDs are awesome, I have one on my big Lagun Mill. Soft start, brake, variable speed, lov'm


Yeah, I havn't put one on my 10hp lathe yet because of cost but I miss the quick stop and miss being able to go as slow as I want. Plus it just seems easier on the machine.

I sell some set up drives to a local heating/ac contractor and he puts them in places where people don't want the noise of a fast fan startup. We put a 3 minute ramp up and down and people don't even know when the system comes on.

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Jeff Pack
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Re: Craigslist deals

Post by Jeff Pack » Wed Jul 02, 2014 10:30 pm

VFDs are awesome, I have one on my big Lagun Mill. Soft start, brake, variable speed, lov'm
=============================================

- I got a good squirt in my mouth
- I would imagine that there would be a large amount of involuntary gagging
- I don't know about you but I'm not into swallowing it

CCR discussion on Caustic Cocktails.

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Desert Diver
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Re: Craigslist deals

Post by Desert Diver » Wed Jul 02, 2014 10:08 pm

I have 3 phase in my shop but still run one lathe on single phase because I put a variable frequency drive on it and it can run off either single phase or three phase. With the vfd you get full horsepower on single phase input but you must oversize the drive because you are only using 2/3 of the rectifiers to charge the capacitor bank in the drive. Additional advantages are the ability to run over or underspeed and soft starts that don't pull such high amperage on startup. I have a bit of experience with variable frequency drives. The first one that I installed in 1987 just burned up in a mill fire this spring (not caused by the drive)

Single phase motors are not really less efficient than 3 phase, they do have more parts to go bad.

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Re: Craigslist deals

Post by Mateo1147 » Wed Jul 02, 2014 9:36 pm

If I may....... With a scrap tthree phase motor and a couple of capacitors anyone can have three phase power in their garage. I run a lathe and two milling machines with a home made rotary phase converter. The one downside to this is that your three phase motors will only produce about 2/3rds their rated HP. You can now get a frequency drive that will convert single phase, 240V power into three phase, 240 volt. Not a bad deal compared to changing out the main compressor motor.
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Re: Craigslist deals

Post by CaptnJack » Mon Jun 30, 2014 10:47 am

GearHead wrote:The page(s) you linked have to be some of the most annoying "click to read more" pages I've run across. They do a fair job of explaining the power distribution grid, but gloss over household power a bit.

You are correct regarding three phase power. I was talking about 120V & 240V power available inside one's house. The web pages don't cover the details of how the two legs of 120V power are created, just that they are 180 degrees out of phase. Perhaps a center tap transformer? Anyway after reading elsewhere, I've found that household power is technically referred to as a single-phase, three-wire system. Two hot wires and one neutral. The 120 volt circuits in our house are one of the hot wires plus the neutral. The breaker box is set up to approximately balance the loads on each of the hot wires.


Yeah sorry, best I could find at 12am .
In a sense you are right that the 2 legs of 230-240V power are supposed to be roughly out of phase by 180 degrees. So they could be considered "2 -phase". But that's not how they are referred to in motor speak. There's only single and three phase.

the single phase motors (2x 120V legs) are so pricey because they are inefficient (relatively speaking)
the three phase (also 2x 120V legs) don't need capacitors and fancy starters because there's no "dead" portion of the phase, since there's always one portion of the sine wave able to do work. Net they are way more efficient and smaller and cheaper per horsepower.

Sadly, none of the other household appliances and motors in your house can handle three phase, they'd burn up. So household current is always single phase and we are stuck with pricey single phase compressor motors with capacitors starters in our garages.

You can change out a three phase for single. Its pretty easy and drop in replacements are typically not hard to find at places like Graingers or Surplus Center.
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Re: Craigslist deals

Post by GearHead » Mon Jun 30, 2014 9:48 am

The page(s) you linked have to be some of the most annoying "click to read more" pages I've run across. They do a fair job of explaining the power distribution grid, but gloss over household power a bit.

You are correct regarding three phase power. I was talking about 120V & 240V power available inside one's house. The web pages don't cover the details of how the two legs of 120V power are created, just that they are 180 degrees out of phase. Perhaps a center tap transformer? Anyway after reading elsewhere, I've found that household power is technically referred to as a single-phase, three-wire system. Two hot wires and one neutral. The 120 volt circuits in our house are one of the hot wires plus the neutral. The breaker box is set up to approximately balance the loads on each of the hot wires.

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Re: Craigslist deals

Post by CaptnJack » Mon Jun 30, 2014 12:04 am

No that's not accurate. 120V is always single phase and there is single and three phase 220V.

Three phase 220V is commercial power and not available at a residence. Three phase is more efficient at high loads which is why that's what's delivered to industrial users. You can exchange a three phase motor for a single phase but the singles are way more expensive.

The three phase wiki is fairly technical but accurate. This is a lil better. Basically single phase has 1 sine wave while three phase power has three and they are offset by 120 degrees.
http://science.howstuffworks.com/enviro ... power3.htm
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Craigslist deals

Post by GearHead » Sun Jun 29, 2014 11:50 pm

Actually, household 120V is single phase, 230 - 240V is two phase. Two phase is what enters the main junction box, and is used for electric stoves, furnaces, water heaters and dryers.

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Re: Craigslist deals

Post by CaptnJack » Sun Jun 29, 2014 11:36 pm

If its in a house its single phase 220V
business/commercial might be single or three phase (220V), you can't get three phase at a residence around here
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Re: Craigslist deals

Post by BillZ » Sun Jun 29, 2014 10:23 pm

jeffgerritsen wrote:Who's got two phase or was he referring to 230 volt outlet required?


spatman wrote:Bauer Capitano Compressor for 1600

http://portland.craigslist.org/wsc/tls/4536726248.html


That runs on 230 - probably 30 amp.

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Re: Craigslist deals

Post by CaptnJack » Sun Jun 29, 2014 12:54 am

H20doctor wrote:Yes the body is delrin.. but both scooters were early protypes, and I wasnt about to throw a 600.00 battery in it , just to have it leak on me.. the other issue was the motor, brushed.. and only one speed.. he said not much faster than a Sierra.. I'm saving my money for a magnus 950 or a Genesis


Good call waiting for what you actually want. I rode one once, many years ago. It was slow. The batteries would have to be custom built as they were lower capacity and lighter. The modern packs are too heavy.
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Re: Craigslist deals

Post by jeffgerritsen » Sun Jun 29, 2014 12:30 am

Who's got two phase or was he referring to 230 volt outlet required?


spatman wrote:Bauer Capitano Compressor for 1600

http://portland.craigslist.org/wsc/tls/4536726248.html

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Re: Craigslist deals

Post by spatman » Sat Jun 28, 2014 1:50 pm

Image

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Re: Craigslist deals

Post by H20doctor » Fri May 23, 2014 9:27 pm

Yes the body is delrin.. but both scooters were early protypes, and I wasnt about to throw a 600.00 battery in it , just to have it leak on me.. the other issue was the motor, brushed.. and only one speed.. he said not much faster than a Sierra.. I'm saving my money for a magnus 950 or a Genesis
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mheyns
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Re: Craigslist deals

Post by mheyns » Fri May 23, 2014 9:22 pm

Thanks Laura,

Yup, before I buy a battery my first step will be a leak and to figure out the buoyancy characteristics. Should help me narrow down suitable batt options. I have a couple ideas I'm toying with if the buoyancy is more negative than I'd like, but the weekend should give me a better idea there.

Thanks for the feedback. :-)

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Re: Craigslist deals

Post by Paulicarp » Fri May 23, 2014 9:05 pm

I went through the "great DiveXtras garage sale of 2014" and picked up a few things I needed. The old proto type sierras were priced right for what they are, and Ben was righteous about the rest of the gems as well.

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Re: Craigslist deals

Post by ljjames » Fri May 23, 2014 8:28 pm

when you start looking at batteries for these scooters, i would recommend taking their buoyancy into consideration. If I remember correctly, these are the early delrin bodies, pre aluminum? You may find them to be a bit heavy and a way to compensate would be a smaller battery, possibly lithium to get the power to weight ratio you might need to get it neutral in fresh water (so you can dive the lake with it). But these could be totally different scoots so maybe none of the aforementioned applies. :)

Either way, probably take it out and float/leak test it in fresh water and see where you are at with regards to buoyancy.
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Re: Craigslist deals

Post by mheyns » Fri May 23, 2014 8:14 pm

Well...I picked up the $350 one. Honestly, it looks in great condition. All terminals and connections seem to be clean, the shroud and props seem to be in brand new cond, trigger seems to work as does the reed switch.

Motor was a 24V brushed motor, one of the early ones before they used brushless, but I'm okay with that. Makes getting it up and running a little easier. :-)

Pretty sure all I really need is a battery. Planning to buy a lipo in the 12-20Ah range. Trick part will be making sure I can get one with a max 20A continuous discharge current rating, but there are some around I think I can get. This one looks promising so far but I'll look around for a while first.

http://www.pingbattery.com/servlet/the- ... ium/Detail

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Re: Craigslist deals

Post by H20doctor » Fri May 23, 2014 5:11 pm

I looked at both scooters today...save your money, going to take a minimum of 1000 dollars to get one going, Ben also wouldn't give me any answers about my questions...nor did he have any way to pressure test those scooters
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Jeff Pack
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Re: Craigslist deals

Post by Jeff Pack » Fri May 23, 2014 12:27 pm

=============================================

- I got a good squirt in my mouth
- I would imagine that there would be a large amount of involuntary gagging
- I don't know about you but I'm not into swallowing it

CCR discussion on Caustic Cocktails.

mheyns
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Re: Craigslist deals

Post by mheyns » Fri May 23, 2014 12:19 pm

I'm hoping to pick up the $350 one within the next couple days and make it a project. Sounds like fun!

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