To be precisely accurate, I call (303) 499-7111, the National Institute of Standards and Time (NIST) atomiclock (WWV on short wave radio)
The HOR (Hear Our Roar) siren’s 2 hp motor can be internally wired for 120 or 240 VAC.
Highest circuit breaker in garage sub panel is 20 amps,o I connecto two circuit breakers to yield 240.
Upon conclusion of the midnight noise pollution, as the siren coasts down, at some RPM it suddenly slows faster. I do not like that.
Does the motor have some kind of internal mechanicabrake?
Or is there a speed switch which closes and causes the rotor to slow from an internal load?
If not much trouble, I wouldike to defeat it.
There is a mechanical switch that closes when the motor is turning slowly. It opens quite soon, probably 1/4 of the motor’s rated speed.
Maybe you should switch to a 3 phase motor since there is no starting coil nor switch for it.
I suppose you could disable the switch and use a relay with a timer that activates it for a fraction of a second during start up, like some refrigerator starting circuits do.
Would it be much trouble to access that mechanical switch?
Does it switch power from start-up coils to running coils? Buthere is no external capacitor.
I could starthe rotor spinning with a woodowel. (Have sounded the siren many times with it.)
We have no three-phase power in ouresidential neighborhood.
My 10-hp Federal Signal 2t22A airaid siren (now tornado siren) is connected to 240 three-phase at my fire station.
It coasts all the way down without unnatural slowing.
I think not all motors have a capacitor for the start coil. You can hear the switch mechanism rub on the rotor if you rotate the motor by hand. You would have to take an end off the motor and then put a ziptie or something in there to force the switch in to the open position where it isn’t rubbing on the certrifugal part on the rotor. I don’t know I’ve never done it. It must be possible to take the part off the rotor completely.
How does it slow the motor?
Does it cause eddy currents in the coils to retard the motorotor?
The siren’s vaned rotor is about 14 inches in diameter.
Fun spinning the rotor flinging air againsthe stator and chopping the airflow through the stator’s ports to make sound!
One thing that bothers me is that I got the impression that you connected the 240 volt motor to two single pole 20 ampere breakers, one on each leg of the three wire power service. If this is what you did, you need to connect the motor to a 2 pole 240 volt breaker. The way you have it connected, if one single pole breaker trips and the other does not, there is 120 volts going to the motor which is a shock hazard if you are servicing the motor and think that the power is off. It is also against the electrical code if you really have powered the 240 volt motor with 2 single pole 20 ampere breakers.
You also don’t want to disconnect the capacitor. My guess is that the motor won’t even start without the initial surge from the capacitor and the motor might even burn out trying to start.
My recommendation since you don’t like the fact that the motor doesn’t slow down at a constant rate is that you replace the tornado siren with a horn like the one used in basketball games. Instead of the siren sounding at midnight, “The Horn Blows At Midnight”. The late Jack Benny would be pleased.
Mechanical friction from the switch interface. Applying DC current (like 12VDC) to the motor will turn it in to a brake.
Since there is no constant torque to overcome, like an air compressor starting, just turning it slowly should get it going. It will start in either direction without the capacitor.
Locked rotor run coil curret is probably 3x run current. It’ll trip the breakers after a few seconds.
Everything was like that before the electrical code required what you describe, having the breakers ganged. All screw in fuse panels are like this. Not such a big deal, learn to live with it.
Thisiren can be wired for 110 or 220. But 110 @ 26 amps exceeds the 20-amp circuit breakers.
Had to wire to 220 @ 13 amps.
Both circuit breakers flipped on and off simultaneously so no 120 V to ground.
Whenoise pollution ended, I disconnecthe cable and haul the siren back into the garage.
Reconnecthe wires to their circuit breakers and replace the panel cover.
With capacitor disconnected I wanted to see if I could starthe rotor turning withe wooden dowel.
Instead, chose to have the capacitor starthe motor and when power off, cut a capacitor wire to learn if the siren coasts downaturally withouthe drop in RPM when it reaches that loweRPM.
Shall try in the closed garage with a board over the air intake to lessen volume.
Even a slowly turning rotor could easily amputate fingers.
@Robert-Gift I didn’t realize the tornado siren wasn’t going to be a permanent installation. I mentioned the business about the breakers because I ran into the problem at my church. Two legs of the 240 volt line shared a common neutral. The insurance company wanted the electrical outlets replaced with GFIs. I shut off the circuit to the outlets I was replacing with the GFIs and as I disconnected the neutral wire I got a spark. The code allows for a common neutral, but it is to be continuous and not broken at each outlet. I tied the neutral leads together with a pigtail using a wire nut. I did the same with the hot side.
As for the start capacitor, I had a refrigerator that had a weak capacitor for the compressor motor. The lights would dim in one part of the house and brighten in the other part when the refrigerator would come on. This was back in the late 1970s. I was using a computer terminal and connecting to the mainframe through a dial up modem. When the refrigerator would kick on, I would lose the connection and have to redial. I had the terminal at home to do research for a paper I was writing. When I would work at the terminal, I would unplug the refrigerator. When I think about the tornado siren and what you are doing with it, a problem occured with a tornado siren on a school building in a neighborhood where I lived. The siren went off one night where there was no bad weather. I had a police scanner and turned it on. Apparently, there was only one person who knew where the circuit breaker was in the building to silence the alarm and the police were trying to locate the man. The warning sounded for about an hour before the person with knowledge of the electrical system was located and transported to the building to shut off the siren.
Last night a new neighbor down the block was setting off fireworks in the middle of our street. I walked down the block with my 24" cast iron pipe wrench in my hand. I told him that if he didnt immediately stop I’d knock him out with the business end of the wrench and then shove the handle up his a$$. He went in his house without another word and peace and quiet resumed.
Concur best to not try to redesign/modify the electric motor. The start capacitor isn’t used as an energy storage device. It’s used to power-up a separate motor winding (electro-magnet) that is oriented 90 degrees to the main winding, done both to help overcome the static starting friction and to get the motor rotating in the desired direction (cw vs ccw). For this scheme to work, the current through that winding also has to be 90 degrees shifted, and that’s the capacitor’s primary purpose.
Thank you.
If I starthe rotor spinning withe woodowel and then switch on power, will it not increase to full speed?
During powerless windown, I wanto cuthe capacitor wire to see if that annoying dip in speed stops.
Our Federal Signal 2t22A tornado siren sounds wonderful in its gradual windown. When one gets close, the vibrations can be felt in one’s lungs.
Could be a treatment for cystic fibrosis!
Some set off professionalooking fireworks. Must bexpen$ive, probably purchased in ?oming.
The best wever do is July Fourth sparklers with some neighbors.
Driving to the mountaihospital, I saw some big fireworks.
The worst situation was telling my wife sheard gunshots because six evenly-spaced reports. In.donesia and the Philippines, usually several people die from falling projectiles,he said.
A Los Angeles police car had a hole through the hood from a falling projectile.