Today's Message Index:
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1. 08:16 AM - Re: Re: AC current reading for Revmaster engine (Paul Eckenroth)
2. 09:39 AM - Re: Re: AC current reading for Revmaster engine (C&K)
3. 10:20 AM - Re: AC current reading for Revmaster engine (user9253)
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| Subject: | Re: 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@gmail.com> wrote:
>
> 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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| Subject: | Re: 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:
> Joe
>
> The Revmaster engine has a definiteproblem 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 damagingheat. Checking the DC
> current after the voltage regulator would not be as indicativesince
> 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 circuitryexisted that would make the AC current readable by
> a DC meter.
>
> Paul
>
> On Mon, Sep 19, 2022 at 8:18 PM user9253 <fransew@gmail.com> wrote:
>
> <fransew@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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Message 3
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| 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?
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=507924#507924
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