[RE-wrenches] Power Factor
boB Gudgel
boB at midnitesolar.com
Sat Aug 1 11:24:17 PDT 2009
Chris Worcester wrote:
> Has he checked the torque on all the battery connections?
>
> Sincerely,
>
> Chris Worcester
> Solar Wind Works
> NABCEP Certified PV Installer
> Phone: 530-582-4503
> Fax: 530-582-4603
> www.solarwindworks.com
> chris at solarwindworks.com
> "Proven Energy Solutions"
>
>
Also, Evidence of a bad battery connection (or bad inverter) should be
obvious if the house lights dim
when the pump tries to start.
boB
> -----Original Message-----
> From: re-wrenches-bounces at lists.re-wrenches.org
> [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Matt
> Sent: Thursday, July 30, 2009 3:25 PM
> To: RE-wrenches
> Subject: Re: [RE-wrenches] Power Factor
>
> Possibly a PF question, or maybe one for Magnum - boB,
>
> One of the guys at work is (almost) running a 3/4 hp sub pump with a Magna
> AE 48. Or rather, he isn't. According to him when he first fired it up, it
> operated the pump just fine. The next time he tried, though. he couldn't
> even get a buzz out of the starter. No workee.
>
> The inverter runs all the other loads in the house fine, just not the pump.
> He can run the pump directly from a 7 kW generator with no issues.
> So, do you think we're looking at a power factor deficit,(I think not), a
> motor starter problem or an inverter issue? I have to admit to being
> somewhat baffled by this one because it ran the pump once, but not after.
>
> Matt T
>
>
> ---- boB Gudgel <boB at midnitesolar.com> wrote:
>
>> boB Gudgel wrote:
>>
>> >>So, because of the different ways of specifying PF, it is always best
>> to think of Power Factor as being the ratio of real (in phase) power, or
>> VA to reactive power >>(VARS or "Volt Ampere Reactive"). That will
>> work in all cases.
>>
>>
>> OOOps ! See, this can get confusing. Reverse what I just said Power
>> Factor... " Definition: The ratio of true power to apparent power" as
>> David Brearley had just posted. Otherwise, that calculation can give
>> you an answer that is GREATER than 1.0 and you don't want that !
>>
>> Had to eat some of my words. I just wanted to point out that the phase
>> shift method was called DPF. Didn't Ian Woodenden do an article on PF
>> recently too ? If not, he or someone probably should in one of the two
>> HP magazines.
>>
>> boB
>>
>>
>>> R. Walters wrote:
>>>
>>>> Power factor expresses the time difference between voltage peak and
>>>> current peak on each of their sine waves. If both current and voltage
>>>> waves are "in time", (their wave peaks match up) power factor is 1.
>>>> If one is ahead or behind the other, it's not. Think about an
>>>> electric motor: we hit it with a voltage wave, and a fraction of a
>>>> second later, it actually moves, and the current wave happens. There
>>>> is a little lag there. Resistive loads like lights have very little
>>>> lag, and big electric motors coming up to speed can have horrible PF.
>>>>
>>> This definition of power factor only applies for linear loads with
>>> only inductance or capacitance (with resistance) and is called
>>> "Displacement Power Factor (DPF) and you will see that on some power
>>> meters.
>>>
>>> For non-linear loads, like battery chargers or computer power supplies
>>> without PF Correction, the current waveform (on an O-scope) looks
>>> nothing like a sine or cosine wave. The current "spikes up" at the
>>> AC voltage peaks. It actually *looks like* it might be in phase, BUT
>>> the current and the voltage do NOT look the same. It's non-linear.
>>> Lower than 1.0 power factor for sure.
>>>
>>> For a grid tie inverter, resistive heater or any load that has a PF of
>>> 1.0, the current and voltage waveform will both look exactly the same
>>> AND there will be no phase shift. They are both linear and all
>>> current and voltage is in phase at every point in the AC cycle.
>>>
>>> So, because of the different ways of specifying PF, it is always best
>>> to think of Power Factor as being the ratio of real (in phase) power,
>>> or VA to reactive power (VARS or "Volt Ampere Reactive"). That will
>>> work in all cases. (Real Vs. Apparent power is the same thing).
>>> Apparent power is what you get when you multiply
>>> your RMS meter's Voltage by the RMS current and is called VA Volt
>>> Amperes) V x A will be the highest measured number, that is unless
>>> the PF = 1.0 in which
>>> case both will measure the same.
>>>
>>> Some of that measured VA, or apparent power will be "in phase" and is
>>> the "real" or "true" power. Some of that VA may be reactive,
>>> (inductive or capacitive that is) and is the "out of phase" portion.
>>> Capacitive and inductive reactance is ALWAYS 90 degrees out of phase
>>> in current and voltage.... It's just a matter of how MUCH of your
>>> power is 0 degrees phase shift and how MUCH of that VA is + or - 90
>>> degrees out of phase. If ALL of the current is in phase with the
>>> voltage, then
>>> the power factor is 1.0. That is, if you lay them on top of each
>>> other, they will look the same on an oscilloscope if power factor = 1.0
>>>
>>> It can get way more complicated that this too, but that's basically
>>> it. Feel free to add to this.
>>>
>>> boB
>>>
>>>
>>>
>>> power meters.
>>>
>>>
>>>
>>>> There is much more to it, with reactance, "real" and "imaginary"
>>>> numbers?!, etc. but basically, we wrenches need to know that
>>>> everybody wants Power factor to be close to 1.
>>>> Obviously there isn't PF on DC, and it is my understanding that most
>>>> inverters can operate at most power factors. Not 100% sure, but I
>>>> think GT inverters would help not hurt the PF problem in most
>>>> situations.
>>>>
>>>> Correct me on any and all of this, Oh fellow wrenches,
>>>>
>>>> R. Walters
>>>> Solarray.com
>>>> NABCEP # 04170442
>>>>
>>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>> On Jul 30, 2009, at 9:19 AM, boB Gudgel wrote:
>>>>
>>>>
>>>>> Ron Young wrote:
>>>>>
>>>>>> Ok, so all seem to be in agreement more or less. How do I break it
>>>>>> to British Columbia Hydro? :-|
>>>>>>
>>>>>> I think they must be misunderstanding what they are asking for but
>>>>>> the question is in the section for PV and on the same line as the
>>>>>> total output in Kwh of the PV. Power Factor %
>>>>>>
>>>>> It was most likely just a trick question.
>>>>>
>>>>> You're gonna fool them, though ! :)
>>>>>
>>>>>
>>>>> boB
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>> I'll contact them and see where this goes but I don't fully
>>>>>> understand what power factor is which will make it hard to argue my
>>>>>> case. My understanding is that it is the difference between what
>>>>>> the utility supplies to a residence vs. the actual loads being used
>>>>>> by that residence expressed as a percentage. I came across the
>>>>>> following course offering by SEI that discusses Power Factor with
>>>>>> reference to PV:
>>>>>>
>>>>>> POWER FACTOR AS IT RELATES TO SOLAR INSTALLATIONS Presented By:
>>>>>> Michael Smith of Alpine Management Systems
>>>>>> This session will deal with power factor: What is power factor?
>>>>>> What causes low power factor? Why improve your power factor? This
>>>>>> session will explain the role of power factor correction as it
>>>>>> applies to solar installations. There are currently over 67,000
>>>>>> KVAR installations in 26 countries resulting in phenomenal energy
>>>>>> savings with a corresponding reduction in greenhouse gas emissions.
>>>>>> Session includes several KVAR installations and the resultant
>>>>>> savings.
>>>>>>
>>>>>>
> http://www.solarenergy.org/workshops/docs/industry08_trainingdetails.pdf
>
>>>>>> Ron
>>>>>>
>>>>>> On 30-Jul-09, at 7:43 AM, Wind-sun.com wrote:
>>>>>>
>>>>>>
>>>>>>> There is no such thing as a power factor for DC or for panels.
>>>>>>>
>>>>>>>
> ............................................................................
> ......................
>
>>>>>>> Northern Arizona Wind & Sun - Electricity From The Sun Since 1979
>>>>>>> Solar Discussion Forum: http://www.wind-sun.com/ForumVB/
>>>>>>>
>>>>>>>
> ............................................................................
> ......................
>
>>>>>>> ----- Original Message -----
>>>>>>> *From:* Ron Young <mailto:solareagle at solareagle.com>
>>>>>>> *To:* RE-wrenches <mailto:re-wrenches at lists.re-wrenches.org>
>>>>>>> *Sent:* Wednesday, July 29, 2009 5:45 PM
>>>>>>> *Subject:* [RE-wrenches] Power Factor
>>>>>>>
>>>>>>> Can anyone point me in the direction to find the power factor
>>>>>>>
> for
>
>>>>>>> Sanyo HIT N 205 panels? The utility is requesting it on a net
>>>>>>> metering interconnection application. Ron Young
>>>>>>> earthRight Products - Solareagle.com
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
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