Slow 2t22 rise by wiring motor to 480V on 240V supply?

[Robert Gift]

... I personally think you should mount the 2T22 on a pole made of Inconel 718 with integrated resonant cavities, waterproof the whole thing, and mount it inside the digester, so the water can amplify the sound. ...

Great idea!
Then no one would try to steal it and scrap it for copper.
Resonant cavities? That's a nice touch!
Confucius say: Thief who fall in digester have ****ty death.

[bobc455]

Immediately after start-up of the three-phase 2t22 motor, I'm too scared to switch open one leg of three-phase power to slow the rise.

So, can I safely run the motor undervoltaged?

The coils are connected for 208-240 operation on the 240 power we have.

What if I reconnect the coils for 480 V input on the 240V supply?

If it were a DC motor, that could work.

An AC motor will try to go the speed according to the frequency it's given. so a 60 Hz motor will try to go whatever RPM it was designed for (usually 1800 or 3600 RPM). It will try to go that speed by "sucking" the number of amps necessary to go that speed. Since the voltage is lower, it will try to draw a ton more amperage than the wiring was designed for and burn up.

Therefore you can't run the motor undervoltage.

Also you can't just run it on one leg. 3-phase motors don't work that way.

-Bob Cunningham

[Robert Gift]

... Since the voltage is lower, it will try to draw a ton more amperage than the wiring was designed for and burn up.

But if I place two coils in parallel for 240V in series for 480V, would that provide enough resistance/reactance to minimize too much amperage through the two coils now in series?

Also you can't just run it on one leg. 3-phase motors don't work that way.

-Bob Cunningham

I wanted to start in three-phase and drop one leg.
With a phase converter, is the third leg not weak?
I assume if I dropped the third leg, the remaining two would provide enough to accelerate, albeit slower, somewhat similar to being connected to a phase convertor.

Thank you for educating me on this.

[JasonC]

But if I place two coils in parallel for 240V in series for 480V, would that provide enough resistance/reactance to minimize too much amperage through the two coils now in series?

Motors are inductive, NOT resistive loads; it doesn't work like that. You'll fry the motor as the windings become saturated with many amps. That's why they make highly advanced (and $$$) variable frequency drives, they are the ONLY way to reliably slow down a 3 phase motor, and even then you still have to watch it.

If you want to use a static converter, go for it. They have a very high failure rate, and will be useless when you need it most. There's no reason to drop a leg off of a in service warning siren. If you want a siren to play with, get one that's not in actual use.

This topic is starting to beat a dead horse....

[azman798]

But if I place two coils in parallel for 240V in series for 480V, would that provide enough resistance/reactance to minimize too much amperage through the two coils now in series?

Motors are inductive, NOT resistive loads; it doesn't work like that. You'll fry the motor as the windings become saturated with many amps. That's why they make highly advanced (and $$$) variable frequency drives, they are the ONLY way to reliably slow down a 3 phase motor, and even then you still have to watch it.

If you want to use a static converter, go for it. They have a very high failure rate, and will be useless when you need it most. There's no reason to drop a leg off of a in service warning siren. If you want a siren to play with, get one that's not in actual use.

This topic is starting to beat a dead horse....

I agree plus, who cares that the siren winds up to fast! Its only going to be YOU that knows. I am sure other people don't give a crap! They don't care as long as the siren does the job! Jeez get it in your head! If it still bothers you then don't install that siren wait and get one with a slow wind up!

[jmev]

I have a better idea. I'll trade you a weak model 5 for the 2T22. The model 5 is guaranteed to wind up slow! You'll like this one that I'm taking down tomorrow (no- it's not for sale! I need parts from it, so it will become an organ donor). It takes about 15 seconds to reach full speed. It gets replaced with a real siren- a Sentry 7V8-1

By the way, none of this technical masturbation will ever work. Removing a phase will stop the motor. Running at the 480 setting will possibly not even allow the motor to start, as I just tried to start on STH10 240V single phase on 120VAC yesterday just to see what happened. It hummed and spun a few RPM, but didn't have the balls to even make ANY sound. It is certain to overheat and/or trip the thermals on the starter.

If anything would ever work, try a small section (5-10') of #8 or #10 wire before the siren. This small section of undersized cable will cause enough voltage drop to do what you want, but will have the side-effect of heat coming from the wires. This is DANGEROUS, but could be fun to try for a one-time experiment. As for NEC, there are many barns, garages and sheds around here that are fed by underground cabling and plugged into the house with a 240 plug. The local nazi inspectors don't like it, but have no authority over it. There are many NEC loopholes, but NEC is in place for safety, so why mess with it? Also, FEMA and other government bodies would be really pissed if they saw a storm or other evacuation system installed that was modified like this to make it sound "like you think it should." Just install it and make it work as FedSig intended. I hate the sound and coverage of any electronic "siren" (cough cough) ever built, but I'm not going to rework the tone boards or amplifiers to make it sound better. It is what it is and that's it. Let it be. The 2T22 is the most musically-pleasant siren ever built.

As already stated, nobody will ever know the siren winds too fast (which by the way, doesn't). I work on these things and still can't always tell what siren is what since there are many variables involved. If you think a 3-phase winds fast, you should hear some of the single phase 2T22s that wind up REAAAAALY fast.

Okay now...can we seriously end this topic already?

-my ignored opinion

[Justin]

The problem with the sewage plant is that the siren is too low.

How low exactly?

Look, the 2T22 is for warning; not for f***ing around with. If you fry the motor. That's it. End game. Waste more money sourcing another motor or worse: a whole new siren.

Bite the bullet and sink a relatively long telephone pole in the sewerage treatment plant, mount the 2T22 on top of it and set up a radio connection between the fire station and the siren controller.

Your objective is to warn the community, not make the 2T22 sound 'technically correct'.

For Google Earthers:
39?44'12.12"N 104?40'38.11"W

[Robert Gift]

Thanks.
You are all correct.

I wanted only to try this if it was safe and easy to do.

The siren is mounted on it's metal tripod temporarily on a 36? inch high mobile home stairway platform.
The platform is securely tied to the solid digester hand rails.

We don't have the money to plant a pole in the treatment plant property.
It will be mounted on the fire station roof.

Thanks.

[pyramid head]

Having it on the roof is a much better idea anyways. But if you did want it on a pole, why not do a few fund raisers for the project?

[Robert Gift]

Having it on the roof is a much better idea anyways. But if you did want it on a pole, why not do a few fund raisers for the project?

I prefer a pole because it would be higher than the station roof. It is also technically a separate structure which avoids the "two services to one structure" complication.
But they are very poor. No money for anything.
But the roof mount will be heard throughout the trailer park.
(If you all aren't nice to me, I'll paint the siren white with 101 black spots all over and name it Poindexter!)