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AC current reading for Revmaster engine

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Paul Eckenroth

Joined: 29 Jun 2010
Posts: 14

Posted: Mon Sep 19, 2022 12:19 pm Post subject: AC current reading for Revmaster engine

I have described previously the problems with my Revmaster engine and the destruction of it's stator.  As I am slowly reassembling my firewall forward I've incorporated a DC current sensor and various temperature sensors trying to create an early warning system to catch a over temp and over current episode before the stator is again burned up.  It occurred to me that rather than focusing on the DC current I should be monitoring AC before it is modified by the voltage regulator.  My GRT current sensor can be used for AC or DC but the GRT EIS cannot process the AC generated signal. So, my question: can I modify the signal from the sensor so that the EIS can give me a reading. Thanks for your help.



Paul

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user9253

Joined: 28 Mar 2008
Posts: 1944
Location: Riley TWP Michigan

Posted: Mon Sep 19, 2022 4:16 pm Post subject: Re: AC current reading for Revmaster engine

Measuring the AC current will only provide an indirect indication of high 

temperature, which can damage the stator windings.  You are better off 

measuring the stator temperature directly using thermocouples or 

thermistors or whatever is compatible with the GRT.  High AC current is not 

necessarily a problem unless it leads to high temperature.

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_________________
Joe Gores

N509RV(at)eckenroth.com
Guest

Posted: Thu Sep 22, 2022 7:16 am Post subject: AC current reading for Revmaster engine

Joe



The Revmaster engine has a definite problem dealing with heat in the stator and since the heat in the stator is varied by the current generated, I figured that the AC current would be a good thing to monitor to try and anticipate the damaging heat.  Checking the DC current after the voltage regulator would not be as indicative since there would be some loss in the regulator and if the regulator is the shunt type DC current would not represent what the stator is actually producing.  I do have thermocouples in the stator but the GRT EIS cannot read a thermocouple except as an EGT or CHT input. I was hoping that some circuitry existed that would make the AC current readable by a DC meter.  

Paul

On Mon, Sep 19, 2022 at 8:18 PM user9253 <fransew(at)gmail.com (fransew(at)gmail.com)> wrote:



 	  Quote: 	
		  --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>

 

 Measuring the AC current will only provide an indirect indication of high 

 temperature, which can damage the stator windings.  You are better off 

 measuring the stator temperature directly using thermocouples or 

 thermistors or whatever is compatible with the GRT.  High AC current is not 

 necessarily a problem unless it leads to high temperature.

 

 --------

 Joe Gores

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=507910#507910

 

 

 

 

 

 

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yellowduckduo(at)gmail.co
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Posted: Thu Sep 22, 2022 8:39 am Post subject: AC current reading for Revmaster engine

I have devised such circuitry for real time vibration monitoring and 

such but it takes a little tinkering.  The signal is 2.5 volts at zero 

current and you use a "perfect" diode to rectify that signal that is 

alternating around the 2.5 level and then add a capacitor and resistor 

to ground to filter it. The tinkering comes from the fact that voltage 

drop through conventional diodes is a deal breaker.  So I use an op amp 

or instrumentation amplifier to essentially be a perfect rectifier.  Add 

a variable resistor to adjust the gain of the circuit for calibration. 

Cost is under $5. You can offset the result by 2.5 volts (with an op 

amp) if you want zero output at zero current but if memory serves I 

think you can adjust the EIS input offset parameter to skip the voltage 

offsetting step.



However do you really have a shunt type regulator?  I have proven that 

some commonly believed shunt regulators are not shunt regulators just be 

monitoring their temperature.  Does it heat up or cool down with higher 

load is a good enough answer for me. If it is not a shunting unit then 

there is little point in measuring the ac current.  Regardless I agree 

that the temperature of the stator combined with dc output current would 

be enough information to satisfy me.



I find that the real value of monitoring such data is to record the 

serial output from my GRT EIS4000.  I use an arduino to record to an sd 

card and look at it later but as I recall a laptop also works for short 

term monitoring.

Ken



On 22-Sep.-22 11:16 a.m., Paul Eckenroth wrote:

 	  Quote: 	
		   Joe



 The Revmaster engine has a definite problem dealing with heat in the 

 stator and since the heat in the stator is varied by the current 

 generated, I figured that the AC current would be a good thing to 

 monitor to try and anticipate the damaging heat.  Checking the DC 

 current after the voltage regulator would not be as indicative since 

 there would be some loss in the regulator and if the regulator is the 

 shunt type DC current would not represent what the stator is actually 

 producing.  I do have thermocouples in the stator but the GRT EIS 

 cannot read a thermocouple except as an EGT or CHT input. I was hoping 

 that some circuitry existed that would make the AC current readable by 

 a DC meter.



 Paul



 On Mon, Sep 19, 2022 at 8:18 PM user9253 <fransew(at)gmail.com> wrote:



     

     <fransew(at)gmail.com>



     Measuring the AC current will only provide an indirect indication

     of high

     temperature, which can damage the stator windings.  You are better

     off

     measuring the stator temperature directly using thermocouples or

     thermistors or whatever is compatible with the GRT.  High AC

     current is not

     necessarily a problem unless it leads to high temperature.



     --------

     Joe Gores





     Read this topic online here:



     http://forums.matronics.com/viewtopic.php?p=507910#507910

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user9253

Joined: 28 Mar 2008
Posts: 1944
Location: Riley TWP Michigan

Posted: Thu Sep 22, 2022 9:19 am Post subject: Re: AC current reading for Revmaster engine

Ken offers good advice about monitoring the voltage regulator temperature 

to determine if the regulator is the shunt type or not.  If the voltage 

regulator is NOT the shunt type (most likely), then there is no sense in going 

to the trouble of measuring the AC current when monitoring the DC current 

will give the same information.  If the voltage regulator temperature goes up 

with increasing load, then the regulator is NOT the shunt type.  Even if the 

regulator IS the shunt type, then it wouldn't do any good to measure the AC 

current because it would always be at maximum regardless of the DC load 

and you couldn't do anything about it anyway.  So the best thing to do is to 

determine if the voltage regulator is the shunt type, and if it is, then replace 

it with a switching type.

  If you are determined to measure the AC current, then the easiest way is to 

temporarily use a multimeter with a current clamp.  It is possible to design 

and build a circuit to measure the AC current and display it on your GRT.  But 

why do that when it is not necessary?

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Joe Gores

dj_theis

Joined: 28 Aug 2017
Posts: 68
Location: Minnesota

Posted: Fri Sep 23, 2022 4:43 am Post subject: Re: AC current reading for Revmaster engine

 	  Quote: 	
		   Checking the DC current after the voltage regulator would not be as indicative since there would be some loss in the regulator and if the regulator is the shunt type DC current would not represent what the stator is actually producing. 	




I’ve measured and analyzed the Revmaster charge system numerous ways.  The OEM regulator is NOT a shunt regulator.  Trying to measure the AC current will provide absolutely no advantage (unless you are replacing the original regulator with a shunt,…). A shunt regulator will effectively double the heating of the worst case charging (the original regulator is a half wave, not a full wave).  I would strongly advocate using the original equipment regulator. And definitely not installing a shunt regulator.



This charge system has (at least) 4 flaws.  1) low air flow/cooling. 2) erroneous stator design with magnetically saturated laminates.  3) no resin coating infusion on the windings 4) low air flow/cooling.



I injected DC current from a lab supply through the stator winding on the bench and measured the rise in temperature of the surface of the stator wire and the center laminate steel.  I’ve concluded that continuous DC at 15 amps with an ambient temperature of 100 F will not create a temperature rise that is damaging (steady state of below 140 F).  I can forward the temperature curves if anyone is interested.



Increasing air flow is job 1, wrt cooling this stator.  Impregnating the wiring is an improvement that I advocate but do not have data on it.  My direct conversation with the stator wire manufacturer, and their recommendation suggests to me it would be an improvement.   I can share the method of impregnating the stator wiring that I’m using with the “web”, but I’m reluctant to advertise this until I can verify there is no damage to the ignition coils.  I’ve tested impregnation on the stator coils but the locally mounted ignition coil wire is different (much smaller and from an unknown supplier).



Hope this helps,



Dan

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_________________
Dan Theis
Scratch building Sonex #1362
Revmaster Alternator problem solved.

N509RV(at)eckenroth.com
Guest

Posted: Sun Sep 25, 2022 5:23 am Post subject: AC current reading for Revmaster engine

Thanks to Joe, Ken, and Dan for your comments.  I will be monitoring the temps of the stator coils and the voltage regulator.  The voltage regulator I will use will be the "John Deere type which I've been told is the switching type.  I have been told by Revmaster that their regulator is the shunt type.  Unfortunately there seems to be no way of knowing for sure beforehand what type of regulator a specific unit is.  That information is not included in any descriptions.  I have enlarged the ventilation areas in the case and will direct blast air directly to the stator.  I'll return the plane to service soon and see what happens.  This is hardly the ideal situation when completing an airplane.  Thanks again.



Paul

On Fri, Sep 23, 2022 at 8:45 AM dj_theis <djtheis58(at)gmail.com (djtheis58(at)gmail.com)> wrote:



 	  Quote: 	
		  --> AeroElectric-List message posted by: "dj_theis" <djtheis58(at)gmail.com (djtheis58(at)gmail.com)>

 

 

 >  Checking the DC current after the voltage regulator would not be as indicative since there would be some loss in the regulator and if the regulator is the shunt type DC current would not represent what the stator is actually producing. 

 

 

 I’ve measured and analyzed the Revmaster charge system numerous ways.  The OEM regulator is NOT a shunt regulator.  Trying to measure the AC current will provide absolutely no advantage (unless you are replacing the original regulator with a shunt,…). A shunt regulator will effectively double the heating of the worst case charging (the original regulator is a half wave, not a full wave).  I would strongly advocate using the original equipment regulator. And definitely not installing a shunt regulator.

 

 This charge system has (at least) 4 flaws.  1) low air flow/cooling. 2) erroneous stator design with magnetically saturated laminates.  3) no resin coating infusion on the windings 4) low air flow/cooling.

 

 I injected DC current from a lab supply through the stator winding on the bench and measured the rise in temperature of the surface of the stator wire and the center laminate steel.  I’ve concluded that continuous DC at 15 amps with an ambient temperature of 100 F will not create a temperature rise that is damaging (steady state of below 140 F).  I can forward the temperature curves if anyone is interested.

 

 Increasing air flow is job 1, wrt cooling this stator.  Impregnating the wiring is an improvement that I advocate but do not have data on it.  My direct conversation with the stator wire manufacturer, and their recommendation suggests to me it would be an improvement.   I can share the method of impregnating the stator wiring that I’m using with the “web”, but I’m reluctant to advertise this until I can verify there is no damage to the ignition coils.  I’ve tested impregnation on the stator coils but the locally mounted ignition coil wire is different (much smaller and from an unknown supplier).

 

 Hope this helps,

 

 Dan

 

 --------

 Dan Theis

 Scratch building Sonex #1362

 Still working on the Revmaster Alternator improvement

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=507925#507925

 

 

 

 

 

 

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