And this website may be useful for calculating generator size and power calculations on line.

http://www.macgen.com/calcul.html

If your total load requirement is 14Kw. Then 14Kw = 80% of 17.5Kw (22Kva rounded up) so a 22Kva generator would be the optimum size... It doesnt appear however, that your 14Kw load requirement was calculated using the starting wattage for all of your a/c units; if the 14Kw load was for your 19 a/c units alone (not including your other electrical appliances), it would mean an average starting wattage of just over 700watts per unit... this can't be correct, can it...?

of course i did not consider all aircon units for a rational but still comfortable solution all aircons together draw 28 kilowatts = >120 amps = minimum starting amps exceeding 250 amps! they would even overload my present three-pase connection of 3x30 amps even though i was told that in (amazing) Thailand i can overload by 100% continuously and 150% for "short time" but that is academic only but it happens 3-4 times a year when 14 or 15 aircons are running full blast from evening till next morning after i receive a message saying "tomollow no power flom 08.00 till 16.00 hrs because habb lepair erectricity our area".

what i considered is

kitchen: two huge fridges/freezers each 800 watts, one microwave 1200 watts and 250 watts lighting

my study: one aircon 13,000 btu 1100 watts and miscellaneous electronics 600 watts

wife's study: one aircon 13,000 btu 1100 watts and miscellaneous electronics plus TV 1000 watts

TV-room: one aircon 13,000 btu 1100 watts plus TV, sat-receivers, harddrive recorders 100 watts

master bedroom: one aircon 13,000 btu 1100 watts

pressurised water supply: two pumps each 800 watts

starting amps apply only to the fridges and one aircon as the aircons are switched on manually one by one

total: max 10 kilowatts

This post has been edited by genset: 2009-10-30 08:25:04

The KDE20SS3 is a Super Silent, 17Kva (13.6Kw) 3 phase set, same specs as the KDE16SS, but the former is 3 phase, rated current is 24.5amps per phase. For your information, I'll paste the specs and price tomorrow if I get a chance.

thanks Genset. i think that unit would be perfect for my demands. the higher price for a three-phase unit might be compensated by the big advantage that power is not limited to certain areas. but i still have a problem understanding the calculation "3x24.5 amps = 13.6 kW".

24.5 amps @ 220 volts = 5390 kW x 3 = 16170 kW. do i miss something?

This post has been edited by Naam: 2009-10-30 15:06:46

Hi Naam,

I should have given you the formula for calculating amps from Kw when using a 3 phase generator, my apologies.

Amps = (Kw x 1000) / (Voltage x Power Factor x 1.73 (the square root of 3 for a three phase supply)), therefore;

Amps = (13.6 x 1000) 13600 / (400 x 0.8 x 1.73) 553.6

Thus, 13600 / 553.6 = 24.5 amps per phase

Thanks for picking me up on this Naam, hope this clears up the confusion..

Genset




This post has been edited by genset: 2009-10-31 20:17:45

Dont want to dissapoint you,you seem to know what your talking about, but i purchased 1 off these generators not from you and had problems with it so changed it for another 1 and again had problems got refund in the the end had a different control panel on though,now purchased a kyoto bright orange genny run for 150 hrs so far no problems,

It would be useful to all if you could briefly detail the issue you had with this unit, was it related to the control panel which you have now replaced?

Hi RobM,

Not dissapointed, I appreciate your comments, there is no point in ignoring maintenance or reliability issues if they have occured. As with any product, there will always be occasions when defective units or operational/reliability issues are raised. I appreciate the opportunity to discuss it.

I dont know how long ago you purchased the generator, but the first generation KDE6700TA featured a different control panel as you mentioned, there were also problems with the fuel pump on some units. Prior to and in anticipation of CE Conformity Certification, both faulty aspects (the digital control panel and pump) of these machines were upgraded and that seems to have remedied the issues. I would hazard a guess that the machine you purchased was indeed a first generation model (perhaps old stock), it seems to fit the profile.

As you can see from the CE certificate for the KDE6700TA, it received certification in December 2007, units manufactured prior to that date, did not meet the EU low voltage and machinery directives. I am sorry to hear that you had a problem with the unit you purchased, but I do not feel that it reflects on the standard of the model KDE6700TA currently being manufactured by Kipor.

I am happy to hear that you were able to exchange the unit and subsequently get a refund. The distributor I have aligned with in Bangkok offers a 12 month warranty on all generators and are very attentive to requests by customers for warranty repairs or replacement of parts.

Genset



This post has been edited by genset: 2009-10-31 01:08:58

In simple terms, a leading power factor will cause a synchronous generator internal voltage to increase. The electronic AVR will sense this increase in internal voltage and decrease the generator excitation. At some point the AVR will tend to loose control of the generator output voltage due to low excitation. This can be a huge problem when working with paralleled, load sharing generators. The generator kvar capacity curves will indicate a design leading power factor limit. A lagging power factor will reverse this tendency of the AVR to loose control.

UPS and electronic loads present a different problem, one of harmonics and waveform distortion from non-linear power supplies. Most cheap electronic AVRs use average sensing and the zero crossing point as a control reference. Since the voltage waveform is distorted, the reference point is not stable, the SCR gating signal is not stable, and the AVR output tends to fluctuate. A true rms sensing (digital) AVR may be required if this becomes a significant problem.

Residential electrical systems usually operate at a lagging power factor without significant UPS loads. If you have a leading power factor, then you usually have harmonic (waveform distortion) problems associated with a lot of non-linear loads.

This post has been edited by genset: 2009-10-31 15:31:02

Here is an example of a standby generator system in a hospital ( Australia)

Main Switchboards were divided into essential and non essential loads.

2 x 875KVA 4 pole 50hz generators. Auto start on mains failure or undervoltage.
Generators connected to an ATS. Generators run in parallel (auto synronisation)

On line within 20 secs of mains failure, 20min run on time.

One of the areas supplied was the IT centre and it was equipped with a 20KVA
3 phase UPS which was designed to carry a fixed load for 30mins. This of course
was when the batteries were new and depended on the actual load being supplied.

There were numerous small UPS units supplying computers and medical monitoring
equipment.

Airconditioning was sequence started. There were numerous VSDs within the HVAC
system.

System PF was generally between 0.85 an 0.9

And there was never any problem with harmonics or voltage stability.

The UPS used on medical equipment did not have split mode power supplies as these
tended to bring up alarms on LIM units due to their high standing leakage current.

Hi David96,

I appreciate your input and understand your point. I dont want this issue to become contentious, I see you have mentioned this in another previous post and would like to draw a line under it if I may.

Nobody is suggesting that you do not have experience of UPS systems (possibly numerous systems) that work faultlessly with a standby generator supply, or that your point is not valid. In post No9 I wrote; 'Some UPS sytems operate ok with generators I have installed, and others experience problems.' I further wrote in response to your comments, post No18; 'My experience is that it is not a major issue in general, but the PDF document is an interesting read regardless'.

That is to say, that not every UPS system operating on a generator supply will experience problems (I dont think that anybody is knocking the value of UPS systems here or suggesting that the problem is widespread and inhibitive...), but under certain conditions, leading power factor can be an issue, and when it is, harmonics and waveform (according to my techy friends at MeccAlte who manufacture good quality electronic and digital AVRs) can be attributed to the problem. Further evidence of how generators can be affected, under certain conditions are highlighted by Mr. Gary Olson, the Director of Power Systems Development at Cummins Power Generation in page two of his white paper, who I believe, is uniquely placed to offer an opinion on this subject.

This from his white paper attached to post No's 9 and 10:

'Over the past years, generator set manufacturers have evolved their equipment designs to include use of digital automatic voltage regulator (AVR) equipment, separate excitation systems, and PWM-type control architecture to enable the generator set to produce and stable output voltage and successfully operate non-linear loads.

At the same time, manufacturers of equipment that has non-linear load characteristics have begun to commonly employ filters to limit harmonic current distortion induced on the power supply. Capacitive elements are also applied in facilities to improve the power factor when operating on the utility source to avoid higher energy charges. While filters provide positive impacts on the overall power system, they can be very disruptive to generator operation.

The generator set AVR monitors generator output voltage and controls alternator field strength to maintain constant output voltage. Relatively low AVR output is required to maintain generator voltage at no load. In the figure shown, the no load exciter field current required is less than half the full load level.

Filter equipment is often sized for operation at the expected maximum load on the UPS or motor load. At light loads there may be excess filter capacitance, causing a leading power factor. Since rectifiers are commonly designed to ramp on from zero load to minimize load transients, leading power factor loads may be imposed on the system until inductive loads are added to the system or the load factor of the nonlinear load increases.

A utility supply simply absorbs the reactive power output because it is extremely large relative to the filter system and it has many loads that can consume this energy. With a generator set, however, the rising voltage from the leading power factor causes the voltage regulator to turn down and reduce alternator field strength. If the AVR turns all the way off it looses control of system voltage, which can result in sudden large increases in system voltage. The increase in voltage can result in damage to loads, or can cause the loads to fail to operate on the generator set.

A UPS is designed to recognize high voltage as an abnormal and undesirable condition, so it can immediately switch off its rectifier. When it does that, the high voltage condition is immediately relieved (because the filter is disconnected from the generator set) and voltage returns to normal. To the observer, the generator will seem to be unable to pick up the system loads.'

Taken from 'Impact of leading power factor loads on synchronous alternators' by Mr. Gary Olson, the Director of Power Systems Development at Cummins Power Generation.

To summarize, a UPS system may operate without fault, appear not to operate and/or potentially cause problems with the operation of AVRs, but the 'real life' default, in my experience, is that this is really something of a non-issue.

Genset


This post has been edited by genset: 2009-10-31 15:32:47

having spoke to op turns out i had a first generation genny (old one) he seems to be well informed on all types off genny .....

thanks for help and info .....

A 20KVA UPS on 2 x 875KVA generators is not a significant part of the total load, hardly worth mentioning as indicated by the system power factor. Any harmonics (waveform distortion) associated with the UPS would be completely overwhelmed by the other generator loads, hence the stable AVR operation.

no need for apologies i didn't know that there is a difference in calculation.

[(400 volts)(24.5 amps)(0.8 power factor)(1.732 constant)]/1000 = 13.6 KW 3-phase power

Hi Naam,

These are the specs for the KDE20SS3 I mentioned in my earlier post to you.

KDE20SS3 – 17Kva Rated as a PRP Generator (Prime Power).

• Significant step up in performance and reliability. Static set, in Super Silent canopy, on skids, weighs 790Kg.
• Manufactured to CE standards (EU Machinery Directive 98/37EC and EU Low Voltage Directive 2006/95/ EEC).
• 17Kva (13.6Kw) as a PRP set and 20Kva (16Kw) as an LRP set. This set will easily power a large home, with AC's, and numerous electronic appliances.
• This is a Super Silent Generator set, enclosed in a well constructed soundproof canopy;The unique air handling system reduces the bulk of the engine noise. A double muffler and the use of high quality acoustic absorbing material result in maximum silencing. Unit operates at 51db/7m on a full load, very quiet.
• Electronic AVR voltage regulation.
• Brushless, 3-phase, self exciting, 4 pole alternator.
• In-line 4 cylinder, four-stroke, water cooled, direct injection diesel engine.
• KDE20SS3 operates at 1500rpm, producing three phase, 400v p-p @ 50Hz, and delivering approx 24.5 amps per phase of useable power as a PRP set and 28.9 amps per phase of useable power as an LRP set.
• Electric start, the unit also features a digital control panel with a remote start facility and additional features such as a periodical exerciser function.
• Unit features ATS connections and is compatible for use with an automatic transfer switch. This enables completely automated operation in the event of a power failure or deep brown out.
• 12 hours runtime when loaded and fully fuelled.
• Access points for fuelling, adding coolant etc are conveniently located on the exterior of the generator canopy. Taps to drain and refill engine oil are conveniently located along the skid for ease of maintenance.
• Unit must be grounded.
• 12 months warranty.

Price including VAT from distributor;

KDE20SS3 – 220,000 Thb

These generators can also be seen on my website at http://www.generatorsolutions.org/#/need-a...ator/4534282010

This post has been edited by genset: 2009-11-08 03:03:58

Hi Naam,

Please disregard, the information I gave you in an earlier post regarding recalculation of the KDE20SS3 amp rating for use in Thailand.

The rated amperage per phase for this set is 24.5amps @ 400v p-p, 50hz. I have been reminded by InterestedObserver (who I would like to thank for keeping me on my toes), that my amended calculation (using 220v and thereby increasing the amperage rating) can only be made if these alternators are dual rated (a dual rated aternator is wound with copper wire of a sufficient thickness and thermal insulation of a sufficient grade to withstand the increased temperature associated with increased amperage for dual voltage use. Amp ratings will normally be stamped on a data plate for available voltage configurations). The alternators I work with on a daily basis are indeed dual rated, but 3 phase Kipor alternator on the KDE20SS3 is rated to produce a maximum 24.5amps per phase at 230/400v period.

I have made a point of stressing the need to size alternators correctly (suggesting maximum load requirement at 70-80% of the alternators maximum load rating) precisely to avoid the potential for thermal damage to the alternator windings, so I would like to apologize for dropping a boll*ck on this one.

It is still possible to adjust the AVR to produce 220/380v for use in Thailand, but the rating of 24.5amps per phase will remain the maximum rated output when used as an LRP set and 19.5amps per phase as a PRP set.

Apologies for the confusion and happy to see that these posts are actually being read and scrutinized... I'll try not to let it happen again...

Genset

This post has been edited by genset: 2009-11-01 02:22:57

here's the formula provided by genset:


Amps = (Kw x 1000) / (Voltage x Power Factor x 1.73 (the square root of 3 for a three phase supply)), therefore;

Amps = (13.6 x 1000) 13600 / (400 x 0.8 x 1.73) 553.6

Thus, 13600 / 553.6 = 24.5 amps per phase

This post has been edited by Naam: 2009-11-01 04:30:42

I am waiting for the distributor to get back to me with the latest price, I will add it to the post when I receive it and PM you to let you know.

can't you shoot from the hip?

weighs 790Kg

big crane needed. distance from roadside to projected installation site straight 15-16m plus must be lifted over servants quarter 4.5m high

Electric start, the unit also features a digital control panel with a remote start facility and additional features such as a periodical exerciser function.

remote start facility a must. what's an "exerciser function"?

Unit features ATS connections and is compatible for use with an automatic transfer switch. This enables completely automated operation in the event of a power failure or deep brown out.

automatic transfer (unfortunately) not possible as most probably too many consumers online when brown out or complete black out happens. have to re-evaluate my situation as rewiring of mandatory consumers to one phase should make it possible to use automatic transfer. anything wrong in my thinking?

additional information: brown outs of one or two phases happen quite often. i spent a fortune on replacing burned pump and compressor relays till i had a gadget installed which shuts off a phase completely if voltage drops below a certain value (value can be adjusted, settings are presently at 200 volts).

I am in the process of calculating all my equipment i have to opperate a large selection of fish tanks, all the pumps and various items are marked in w, i have a chiller that has the following info Electrical current 4.2A, Power 1 1/4 HP. Can someone please inform me what this amounts to in W.

Genset-- I know the Cummins document very well; the challenge is finding reliable capability curves for any system. Specific to Cummins, even their MW class machines choke on a few hundred kVAR... and don't get me started on their dam_n MCRS system.

But specific to readers needs, computers and UPS systems do create enough of a leading power factor to cause a problem for a generator designed for 0.8PF lagging loads. Inverter-based AC systems don't help things either.

So, my question remains-- do you have a capability curve for the generators you are representing?

Electrical Horsepower: 1HP = 746 Watts, so 1.25HP = 933 Watts. That's the best answer you can get without getting into all sorts of electrical stuff such as motor efficiency, power factor, rated voltage etc.

[quote name='genset' date='2009-10-28 09:11:28' post='3102616']

Genset,

I plan to use a combination of solar power and a genset. What is your opinion of this. Also I have considered using propane in my home and had thought with a larger propane tank, I could power a genset with it also. What do you know of Propane powered gensets. I realize there could be a conversion from Gas to Propane but is that common in Thailand?

Do you mean they choke on a few hundred kVAR with a leading PF? The capacity curves will indicate the limit, but the reactive power control system (AVR or kVAR/PF controller) is another subject. Knowledgeable power system professionals avoid leading PFs like the plague.