[RE-wrenches] Power Factor
boB Gudgel
boB at midnitesolar.com
Thu Jul 30 17:16:29 PDT 2009
jay peltz wrote:
> Hi Matt,
>
> I would try a few things, but its very curious to me that the inverter
> won't even get a try out of the motor.
> I've seen plenty of motors not work, but they tried to start.
>
> And given the 7k genny starts it, the 4k inverter should start it too.
> I would check the current under load and surge if possible.
> Check the battery voltage.
> Could be a bad cap on the motor too.
>
> I've got a new meter that measures PF on the way, just for problems
> like this.
>
> jay
>
> peltz power
Shall we try for 4 out of a million plus ?? Maybe it's another
dreaded CBI breaker ?
boB
>
>
>
> On Jul 30, 2009, at 4:03 PM, Matt wrote:
>
>> Unh - hunh, but it will run on the generator. If it didn't, I would
>> go for the bad starter or motor, but it "seems" like the PF could be
>> an issue??
>>
>> Matt T
>> ---- boB Gudgel <boB at midnitesolar.com> wrote:
>>> Matt wrote:
>>>> 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.
>>>>
>>> Sounds kind of like a "pump is broken or worn out" problem, doesn't
>>> it ?
>>>
>>> If there is enough ac voltage applied to the pump, the it should do
>>> ~something~, or lights should dim or some
>>> kind of sign should show itself, wouldn't you think ? Otherwise, I
>>> would suspect it might be a surge problem.
>>>
>>> Is there a pilot light or something ? Maybe a fuse blew or breaker
>>> tripped somewhere ? (when the pump went off?)
>>>
>>> Doesn't sound like a PF problem though... However, since you mention
>>> it, with loads that are not a 1.0 power factor,
>>> at least for displacement power factor, when reactive phase shift is
>>> involved, the inverter must be able to "sink" current
>>> from the stored reactive energy as well as be a source to the motor.
>>> The Magnum does that just fine, as does any other
>>> decent inverter.
>>>
>>> Maybe Tony, Eldon or Gary at Magnum has seen this before ?
>>> 425-353-8833
>>>
>>> boB
>>>
>>>
>>>
>>>
>>>
>>>
>>>> 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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