Author Topic: FREQUENCY SENSOR  (Read 6562 times)

Listerational

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FREQUENCY SENSOR
« on: July 22, 2016, 08:57:57 PM »
Hello,

I would like to automatically disconnect the electrical  load on my generator when it senses that I am out of gas or is turning off for some other reason. I am wondering if a frequency sensor would do the trick. Would anyone please recommend a good frequency sensor for my application? My generator is a
POWER LINE, 10-HP, 7.35-KW.

Thank you,

Jim

Jake65mm

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Re: FREQUENCY SENSOR
« Reply #1 on: July 23, 2016, 12:45:23 AM »
So what you need is a Frequency monitoring relay with adjustable hysteresis, I will work on finding a part number that would work and send you the link.

Jake65mm

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BruceM

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Re: FREQUENCY SENSOR
« Reply #3 on: July 23, 2016, 04:07:19 AM »
Warning, some of the frequency (and voltage) monitoring relays can't cope with low speed engines and non smooth sine waves.  Check with the vendor.

I finally went to a Siemans model for my neighbor's propane conversion of the DES 8/1 with an ST-3.  It does true RMS so is completely waveform and is entirely frequency independent for voltage monitoring.   

mike90045

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Re: FREQUENCY SENSOR
« Reply #4 on: July 23, 2016, 07:22:43 AM »
you could also use a beefy relay with 120V coil.  As the RPM's drop, so does the voltage and the coil will drop, cutting off the load and you don't have to reflash the rotor.
This would work with some fiddling to get to coil to let go before the demag happens.

Jake65mm

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Re: FREQUENCY SENSOR
« Reply #5 on: July 23, 2016, 02:12:35 PM »
I would suggest a voltage monitoring relay over a frequency style, in that link there is plenty to chose from. Ive never actually messed with the frequency relay on a slow speed but it makes since how it wouldn't work well with it. I was going to set one up on my small yanmar homemade generator for a two speed throttle using a solenoid.  
« Last Edit: July 23, 2016, 04:40:22 PM by Jake65mm »

Listerational

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Re: FREQUENCY SENSOR
« Reply #6 on: July 25, 2016, 11:50:14 PM »
you could also use a beefy relay with 120V coil.  As the RPM's drop, so does the voltage and the coil will drop, cutting off the load and you don't have to reflash the rotor.
This would work with some fiddling to get to coil to let go before the demag happens.

That sounds like the craziest idea I have ever heard. I love it....
May I ask the definition of 'reflash the motor'?

Thanks,

Listerational

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Re: FREQUENCY SENSOR
« Reply #7 on: July 25, 2016, 11:55:57 PM »
I would suggest a voltage monitoring relay over a frequency style, in that link there is plenty to chose from. Ive never actually messed with the frequency relay on a slow speed but it makes since how it wouldn't work well with it. I was going to set one up on my small yanmar homemade generator for a two speed throttle using a solenoid.  

The reason that it makes sense is it because the ratios are much smaller than in a 3600 rpm?  60hz/3600rpm  vs  60hz/1000rpm.

dieselgman

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Re: FREQUENCY SENSOR
« Reply #8 on: July 26, 2016, 01:54:36 AM »
Reflash is common jargon for re-magnetizing the rotor with a dc battery or similar power source. The generator rotor will sometimes lose its residual magnetism and thus become unable to start up power generation until the rotor is "flashed" or magnetized once again. One way that a generator loses its residual magnetism is when it is improperly shut down under load.

dieselgman
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BruceM

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Re: FREQUENCY SENSOR
« Reply #9 on: July 26, 2016, 02:51:00 AM »
I would expect that you'd get relay chatter trying to use a relay with resistor to coil as a low voltage cutout, due to the low frequency power pulses on a CS.



 

Listerational

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Re: FREQUENCY SENSOR
« Reply #10 on: July 26, 2016, 10:23:10 PM »
Take your pick
http://www.crompton-instruments.com/downloads/2015/EPP-2040-1115_protectors_201115.pdf

Thanks for all of the instructables This is great stuff....

Looking at the link to Crompton Instruments I did not find any plain voltage monitors but phase and voltage monitors. The one that I believe applies best to my  10HP, 7.35KW, SINGLE PHASE LISTEROID is

  PSF/G3-173/240  http://www.crompton-instruments.com/downloads/2015/EPP-2040-1115_protectors_201115.pdf

Do you think this will work with my single phase generator?

Thank you ....

Jake65mm

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Re: FREQUENCY SENSOR
« Reply #11 on: July 26, 2016, 10:32:11 PM »
Check out page 6 they have over voltage , under voltage , and both on there.

Take your pick
http://www.crompton-instruments.com/downloads/2015/EPP-2040-1115_protectors_201115.pdf

Thanks for all of the instructables This is great stuff....

Looking at the link to Crompton Instruments I did not find any plain voltage monitors but phase and voltage monitors. The one that I believe applies best to my  10HP, 7.35KW, SINGLE PHASE LISTEROID is

  PSF/G3-173/240  http://www.crompton-instruments.com/downloads/2015/EPP-2040-1115_protectors_201115.pdf

Do you think this will work with my single phase generator?

Thank you ....

Horsepoor

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Re: FREQUENCY SENSOR
« Reply #12 on: July 27, 2016, 05:53:10 PM »
I use one of these to pull my fuel rack closed is there is a loss of power out if the generator. For example, if a belt broke, the device would shut the engine down due to loss of power. Same for over heat, separate circuit attached. If I had it to do over, I would have the magnet engage and hold a switch on. Thus when the engine lost power or speed, a big spring would pull the switch into the off position due to loss of power and thus the magnet holding it on would disengage. This system could easily pull a relay.

http://www.murcal.com/Catalog/Rack-Pullers/RP2309B-Push-Pull-Solenoid
GTC 20/2 down rated to 850 rpm - ST 15
Metro 6/1 800 rpm on cart - ST 7.5

dieselgman

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Re: FREQUENCY SENSOR
« Reply #13 on: July 27, 2016, 07:35:03 PM »
I concur with the Energized to Run (ETR) methodology. Some manufacturers used an energized to shutdown (ETS) control system, but those were complex and less reliable. Lister has used a simple Energized to Run safety fuel control solenoid for decades.

dieselgman
« Last Edit: July 27, 2016, 10:58:20 PM by dieselgman »
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Jake65mm

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Re: FREQUENCY SENSOR
« Reply #14 on: July 27, 2016, 09:52:12 PM »
The same theory applies to the Emergency stop circuit on a CNC machine,  normally closed. So in the event of a broken wire of faulty switch it alarms the machine out rather then on a normally open circuit with the same issue the machine will never sence it and when the part pulls out of the vise and is working on getting up to spindle speed and you finding out the E stop button doesn't work.
I concur with the Energized to Run methodology. Some manufacturers used an energized shutdown control system, but those were complex and less reliable. Lister has used a simple Energized to Run safety fuel control solenoid for decades.

dieselgman