Is this a 3 Phase Static Converter?

Uglydog said:
I picked up a 20hp rotary converter. A couple days before I first noticed it was cutting out, I had a short in the factory switch which blew a circuit breaker in the main panel. It's now repaired. Could that have done it?
Click to expand...

Hi Uglydog,
have you tried to perform an amp draw test on the Gisholt??
have you taken a voltage reading from all 3 legs of the converters output?
is your 20 hp converter balanced?

it seems rather odd for your system to have only 2 thermal overloads, can anyone post a wiring diagram or schematic??

mike:))
 
Ulma Doctor said:
Hi Uglydog,
have you tried to perform an amp draw test on the Gisholt??
have you taken a voltage reading from all 3 legs of the converters output?
is your 20 hp converter balanced?

it seems rather odd for your system to have only 2 thermal overloads, can anyone post a wiring diagram or schematic??

mike:))
Click to expand...

Mike,

I thought the same thing? Don't all three phase contactors, have 3 thermals? I also asked him if this was running for a while, and then quit? Or is this a new startup?

Bob in Oregon
 
raross61 said:
Mike,

I thought the same thing? Don't all three phase contactors, have 3 thermals? I also asked him if this was running for a while, and then quit? Or is this a new startup?

Bob in Oregon
Click to expand...

i can't say that all 3 phase overloads contain 3 heaters,
but, i can say that i have never seen a heater type three phase overload without 3 heaters.
 
Ulma Doctor said:
i can't say that all 3 phase overloads contain 3 heaters,
but, i can say that i have never seen a heater type three phase overload without 3 heaters.
Click to expand...

Tomorrow I will take and post some pics of the Gisholts electrical panel. I'll be sure to show the thermals and the only electrical schematic I have.
The electrical short was on the on/off for the Gisholt not the rotary.
Rotary was installed by an apprentice electrician friend, not by me.
 
You guys are fun! Now I will show my age. Thermals have only been required by CODE to be in each current carrying conductor to a motor since the 1968 National Electrical Code. Before that the thinking was that the current flowing through the leg with no thermal was also being shared by one of the two other legs. This is not always true such as when that leg goes to ground or has low impedance to ground. Lots of older equipment only has two overloads on three motor leads.

You are correct in saying that all three legs should have thermal protection.

The heat from the heater melts a solder pot that allows a spring loaded spindle to rotate opening a set of contacts in the control circuit de-energizing the coil to the magnetic starter or tripping the latch mechanism in a manual starter. Some brands of starters have the solder pot in the heater itself, (Square D), and some have the solder pot as a component of the starter overload block itself. (Cutler Hammer). The advantage goes to the solder pot in the heater style. This is because when the heater melts and the spindle spins, a minute amount of solder is usually lost. Next time there is less solder to melt so it trips sooner. Good for the motor, bad for you. This is referred to as nuisance tripping. By merely changing out a six dollar heater you have fixed the problem. If you have the other type you may be able to repair the overload block but usually you will need to replace the whole unit at a far greater cost.

WOW! Do I get windy!

cleardot.gif
 
rdhem2 said:
You guys are fun! Now I will show my age. Thermals have only been required by CODE to be in each current carrying conductor to a motor since the 1968 National Electrical Code. Before that the thinking was that the current flowing through the leg with no thermal was also being shared by one of the two other legs. This is not always true such as when that leg goes to ground or has low impedance to ground. Lots of older equipment only has two overloads on three motor leads.

You are correct in saying that all three legs should have thermal protection.

The heat from the heater melts a solder pot that allows a spring loaded spindle to rotate opening a set of contacts in the control circuit de-energizing the coil to the magnetic starter or tripping the latch mechanism in a manual starter. Some brands of starters have the solder pot in the heater itself, (Square D), and some have the solder pot as a component of the starter overload block itself. (Cutler Hammer). The advantage goes to the solder pot in the heater style. This is because when the heater melts and the spindle spins, a minute amount of solder is usually lost. Next time there is less solder to melt so it trips sooner. Good for the motor, bad for you. This is referred to as nuisance tripping. By merely changing out a six dollar heater you have fixed the problem. If you have the other type you may be able to repair the overload block but usually you will need to replace the whole unit at a far greater cost.

WOW! Do I get windy!cleardot.gif
Click to expand...

Good information, thank you.

Please find the attached photos. Please note this is from a 1936 Gisholt with presumably the original 10hp motor and panel.
I pulled the blistered thermal for your viewing pleasure.

The last pics are of the inside of the motor from the Wells Bandsaw. Yep, Mud Wasp Nests. 3 of them. Motor was getting hot, very hot. Pulled it apart. Blew even more dust out. Lots of it and removed the 3 nests. Still very hot and smoking. The armature (proper term?) was notably rough. Didn't want more thermal problems! I took the entire motor in to be looked at by a local 3 phase motor guy.

Suggestions for the Gisholt thermals?
Thank you,
Daryl
MN

IMG_0777.JPG IMG_0778.JPG IMG_0779.JPG IMG_0780.JPG IMG_0781.JPG IMG_0782.JPG IMG_0775.JPG IMG_0776.JPG
 
Gotta love them mud wasps, they kept my south bend lathe motor from running:angry:

Daryl, the thermals are type N33 many manufacturers make them. but you can still get them from Allen Bradley, Graingers and
McMaster Carr carry them too, try Ebay for giggles while you are at it!!!
here's a link that may explain some things about your type of heaters...

http://literature.rockwellautomation.com/idc/groups/literature/documents/td/815-td002_-en-p.pdf

i hope the info helps out!!
mike:))
 
Daryl,

Well that one picture, blows my theory on cleaning contacts, Man silver alloy? Had to be when they built stuff to last! Sounds like maybe the thermals are just weak, but that also comes back, to confirm that you should amp check each leg and see it they are pretty even!

Bob in Oregon
 
A N33 is kinda too light for a 10 hp motor that's only a little over 13 amps per leg for a size 2 or 15 amps on a size 3
i would go up to N38 ish.
maybe N38 since only 2 legs are being thermally protected and your're gonna be pulling some amps on start up.
the N38 is still in the safe zone for your wiring under , being under 25 amps.


mike:))
 
Copy,
N38 thermals.
Scored some on Ebay.

Check amp on each leg.....
Ah.... got an amp meter.... how do I check amp on each leg?
How do I set the meter?
Where do I connect/touch the probes?
Off the 3 fuses in the box going to the panel in the pics?
Where does the other probe connect/touch to?
Should the motor be Gisholt motor be running or just the Rotary?
 
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