[RE-wrenches] Power Factor

jay peltz jay at asis.com
Thu Jul 30 16:28:13 PDT 2009


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



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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