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Author Topic: Inverters Magnum or Xantrex  (Read 5377 times)
scanzel
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« on: June 29, 2007, 08:38:19 AM »

Are the Xantrex 4024 and Magnum MS 4024 made by the same company even though they show different addresses in Washington? Also opinions on each are appreciated. Is anybody using any of the Magnum inverters? Huh
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Steve Canzellarini
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« Reply #1 on: June 29, 2007, 08:53:54 AM »

Xantrex bought out Heart, Trace, and a few other inverter manufacturers.

Magnum is a seperate company formed by folks who used to work at Trace or one of the other companies Xantrex bought out.  Magnum inverters are supposed to be real good, but they are hard to find.  Some of the RV makers are starting to use them.
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Jerry Liebler
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« Reply #2 on: June 29, 2007, 09:01:31 AM »

If you are looking at the 4024 versions from both companies, be careful.  The Xantrex has a full 60 amp transfer capability while the Magnum has 2 x 30 amp transfer relays. And most important to me is ONLY the Xantrex will supplement, with battery power, a small shorecord to start heavy loads.  This allows, for example, starting an air conditioner on a 15 amp shore cord.  Also the Magnum 4024 has a pretty poor efficiency.
Regards
Jerry 4107 1120   
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« Reply #3 on: June 29, 2007, 03:18:30 PM »

Hi Scanzel,

The Xantrax has a much better control panel then the Magnum too.

In comparason, the xantrax has a fully digital readout of all your parameters like volts, amps, and charge rate both in and out of your batts and land lines.

Magnum has a little more then idiot lights to give you information.  No contest!

Good Luck
Nick-
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« Reply #4 on: June 29, 2007, 03:46:24 PM »

I bought the Magnum MS 4024, Magnum, has over 1100 steps in the sign wave, cant see them on an Oscope.   
Xantrex has around 50 and has to go through 3 transformers to make a clean sign wave. 
Xantrex twice as heavy as Magnum due to extra transformers. 
The bells and whistles of the Xantrex I didnt need and for almost $1k less the Magnum MS4024 was for me.   
I use a Link 10 (E-Meter) on dash to look at batteries, much easier then the control panel of the Xantrex.
   
Its all in what you need for features.
I dont plan on needing the inverter to help if Im on a 15 amp shore cord, cause sooner or later the inverter needs to charge the batteries and A/C and battery charger cant work on a 15 amp service.

My 2 cents,

Mrbill4108
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« Reply #5 on: June 29, 2007, 05:00:26 PM »

Mrbill4108,
    It all depends on the AC.  My 18,000 BTU/h ductlees split uses 13 amps running in 95 degree weather.
Regards
Jerry 4107 1120
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Mrbill4108
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« Reply #6 on: June 30, 2007, 07:10:55 AM »

Jerry,

That still only gives the charger 2 amp and it will take more then that for it to start the charge cycle.  So how is the Xantrex going to charge the batteries?  Which it will try once it uses them.   

Big thing is how often is this really an issue? 
Most parks even the older ones have 30 amp service, granted some say 30 but you may only really have about a 20 amp service. 

As for the transfer relay 2x30 is 60, just tie the 2- 30s together if you don't want to transfer a 50 amp service, Magnum also transfers the neutral in that relay.   One less transfer relay needed. 

Another deciding factor that I didn't mention is when I called both companies only Magnum had someone answer the phone and was willing to answer all my questions before and now after the sale.  Great customer support with Magnum.   

Like I said to me saving $s and not having a few bells and whistles that I most likely didn't really need was my final decision. 

The history of Outback & Magnum, both where started when the engineers that worked for Trace didn't like the way Xantrex was headed.   So they went off and started these two companies.  Both companies where very helpful in giving knowledge of inverters so that I could make up my mind as to what I really needed. 

True the control panel of the Magnum does not give you a lot of info, it gives you the charge mode it's in when charging along with volts and amps of charge. Lets you set incoming line amps from 5-50amps, also lets you set battery charge rate.   That's all I've used so far.  It also has setup and tech modes to run diagnostics on the inverter. 

I have an analog AC volt meter that we've had for years that stays plugged in the kitchen area, that way anyone can see if we are using too much power.  Have the wife & kids trained on that little item.   

Anyway one must figure out what you need the inverter for before you get one.  I wanted one to run an A/C down the road instead of always running the generator. I've had it run both roof A/C's for up to an hour without any problems.  Mostly we use it to run one A/C and when we need two we start the generator.    Also if space is a consideration and the Xantrex is bigger and heavier then the Magnum. 

No matter which one you decide to get Steve, Magnum, Outback or Xantrex, make sure it will do what you want it to do,  that's the bottom line. 
They all seem to make a quality product.

Good Luck,
Mrbill4108
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« Reply #7 on: June 30, 2007, 09:07:03 AM »


I have an analog AC volt meter that we've had for years that stays plugged in the kitchen area, that way anyone can see if we are using too much power.  Have the wife & kids trained on that little item.   
I also prefer an analog meter for troubleshooting, but I do not understand how you can see if you are using too much power with it. Can you explain.
Richard
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« Reply #8 on: June 30, 2007, 09:28:23 AM »

Anyone use TrippLite inverters?  How do they stack up against the Magnum and Xantrex?
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« Reply #9 on: June 30, 2007, 09:32:32 AM »

If you do decide on the Magnum, I have a brand new one in the box that I will sell for $1,875.00 plus shipping. I also have one installed in my coach and am very happy with it.
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« Reply #10 on: June 30, 2007, 10:47:23 AM »

We watch the voltage when we turn things on, if it goes down with say, just the A/C on then we know the power supplied is poor.  We then use power management (watch what we turn).  If you are at a place that has good power, you will not be able to tell if you are using too many amps until you trip a breaker.  The voltage meter just lets you know when the amp draw is too much for the supplied power.   

The meter is just a simple way to watch the incoming power for low voltage.   Remember when voltage goes down amp draw goes up.  So if youre A/C draws 15 amps at 120vac then at 110vac it will be drawing around 16.5 amps or more and the compressor starts to heat up because of the higher amp draw. 
Thats why you should watch the incoming voltage.

We limit our A/C run time when voltage goes below 105vac.  Give the compressor time to cool between cycles.

Mrbill4108
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« Reply #11 on: June 30, 2007, 12:17:50 PM »

Fair enough. Thanks. Sounds like a good idea.
Richard


We watch the voltage when we turn things on, if it goes down with say, just the A/C on then we know the power supplied is poor.  We then use power management (watch what we turn).  If you are at a place that has good power, you will not be able to tell if you are using too many amps until you trip a breaker.  The voltage meter just lets you know when the amp draw is too much for the supplied power.   

The meter is just a simple way to watch the incoming power for low voltage.   Remember when voltage goes down amp draw goes up.  So if youre A/C draws 15 amps at 120vac then at 110vac it will be drawing around 16.5 amps or more and the compressor starts to heat up because of the higher amp draw. 
Thats why you should watch the incoming voltage.

We limit our A/C run time when voltage goes below 105vac.  Give the compressor time to cool between cycles.

Mrbill4108
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« Reply #12 on: June 30, 2007, 05:50:47 PM »

...   Remember when voltage goes down amp draw goes up...


This is not true in a general sense.  It is true only for constant-power loads such as synchronous motors.

Most loads in a coach (air conditioners are the notable exception) are resistive loads.  So when voltage goes down, so does current, in a direct 1-1 relationship.

The formula, Ohm's law, is E=IR (or V=IR if you prefer) where "E" is voltage in volts (RMS volts will suffice for AC loads), "I" is current in amperes, and "R" is resistance in ohms.  When resistance is constant, current varies directly with voltage.

Where the confusion often comes in is when comparing current needs in electrical systems of different voltage.  A 24-volt system will need only half the current of a 12-volt system for a given amount of power.  But that's because you need all different devices for those two systems.  A 10-watt light bulb for a 12-volt system is different than a 10-watt light bulb for a 24-volt system.  They both use the same amount of power, but have different internal resistance.  The formula is P=EI, or P=E^2/R.  When the input voltage on your shore cord drops from 120VAC to 110VAC, the resistance of your light bulbs (or your coffeemaker, toaster, etc.) does not change -- so they draw less current, not more.  Of course, you also get less light (or it takes longer to make toast).

FWIW.

-Sean
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« Reply #13 on: June 30, 2007, 07:00:35 PM »

Hi Sean,

I was wondering about that theory..

In dealing with alot of refrigeration compressors, I often wondered about when voltage drops, why does the amp draw increase.

That only happens with compressors and motors but, not other appliances like light bulbs and so fourth..

How do theese motors know to try and keep a certain rpm?

Thanks
Nick-
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« Reply #14 on: June 30, 2007, 07:06:09 PM »

Are the Xantrex 4024 and Magnum MS 4024 made by the same company ...?

No, they are not.

Quote
Also opinions on each are appreciated.


I have a Xantrex, and, like Jerry, I am very happy with it.  That being said, Xantrex has spiraled into a customer-service quagmire, and it is getting harder and harder to recommend their products.

Other than the customer service issue, well addressed by mrbill, there are several other factors you need to consider:

First off, Xantrex actually now makes two very different 4024 products, the SW4024-MC2, and the SW+4024.  So it's important to know which one you are comparing.  The SW4024-MC2 is actually an older product, but is the one currently marketed (and approved) for mobile installations.  It is, IMO, a better product than the newer SW+4024, as it includes several features as standard that are extra-cost options on the SW+.  Also, the SW+ does not carry the approvals for mobile use, if that matters to you.

Neither of these units includes a ground-to-neutral bonding relay, which complicates the installation, as you will need to add that yourself externally.  The Magnum includes an automatic bond relay internally.

Both of the Xantrex units were designed for grid-tie applications (although the SW4024-MC2 has had the controls for grid-tie removed from the menus).  This means they have the capability to synchronize their output waveforms to that of the input power, which is what enables them to operate in "load support" mode that Jerry mentioned earlier.  They also both have the capability to support both input and output currents of 60A.  The combination of these two features means that you can, for example, run three air conditioners while connected to a 30-amp shore service.  You will be drawing power from your batteries while you do this, but we find it an important and useful feature -- we often run an air conditioner when connected to only a 15A shore service, for example, where that same service then charges the batteries overnight when, perhaps, A/C is not needed.  But we're weird.

The Xantrex units also have separate inputs for grid and generator, and an internal transfer switch.  You might just ignore this, though, because the single-leg/no-neutral design of these switches makes them incredibly difficult to use in a motorcoach application (you can see what we had to go through on this issue here: http://ourodyssey.us/bus-e-ats.html).

In contrast, the Magnum has no internal transfer switch, other than between its own output and AC input.  And that transfer switch is limited to 30 amps of output power.  That being said, it does have a two-pole switch, so you can run a 4-wire, 240/120VAC service through it, but you will be limited to a total of 30 amps per leg.  If you can live with this limitation, it makes installation a snap, and the only external component you will need to add for a generator installation is an external automatic or manual 30 amp three-pole transfer switch.  (BTW, it does not have a neutral-switching transfer switch as someone suggested earlier -- the neutral is hard-wired straight through.  The only neutral switching involves ground bonding.)

The limitations in switches and indicator lights that have been mentioned are easily surmounted by purchasing Magnum's remote control panel, which includes a multi-function knob and a display.

The Xantrex is more efficient (94% vs. 86%), and has a larger battery charger (150 amps vs. 105 amps).  The Magnum is quite a bit smaller and lighter (48lbs vs. 105lbs).

In short, as has already been said, it really comes down to which features are important to you.  Or, if you want the best of both worlds and don't mind spending a bit extra for it, get an Outback.

HTH.

-Sean
http://OurOdyssey.BlogSpot.com
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« Reply #15 on: June 30, 2007, 08:43:23 PM »

If you do decide on the Magnum, I have a brand new one in the box that I will sell for $1,875.00 plus shipping.

I paid a little less than that for a new Xantrex RS3000, Control Panel , and Auto Gen Start Module. Shipped.
All works as advertised nearly two years after install.

Jay
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« Reply #16 on: June 30, 2007, 09:00:14 PM »

I'm going to post the spec charts on some brands.
I also have the RS3000, and the 3 year warranty tops most others.
Nick-


   
RS3000 Sine Wave Inverter/Charger
Designed for RVs to power advanced onboard electronics. The RS3000 features 3000 watts of sine wave output and an advanced three-stage battery charger together with industry-standard networking capability.




Model
RS3000 SW Inverter/Charger 


 
   
 Product Info | Specifications | Document Downloads | Compare 
 
 Specifications

 
 Electrical Specifications - Inverter
 
 
 Output power (continuous)
 
 3000 watts
 
 
 Surge rating (5 seconds)
 
 7500 watts (60 A)
 
 
 Output voltage
 
 120 VAC
 
 
 Output frequency
 
 60 Hz +/- 0.05% (crystal controlled)
 
 
 Output waveform
 
 Sine wave (< 5% THD)
 
 
 Peak Efficiency
 
 > 90%
 
 
 Efficiency (full load)
 
 > 85%
 
 
 No load power draw (search mode)
 
 < 20 W
 
 
 AC connections
 
 Split phase in / dual out, Dual in / dual out
 
 
 AC transfer capability
 
 2 legs at 50 A (split phase in),
2 legs at 30 A (dual in)
 
 
 Transfer time
 
 20 ms (typical)
 
 
 Electrical Specifications - Charger
 
 
 Output current
 
 150 A DC
 
 
 Battery voltage (nominal)
 
 12 VDC
 
 
 Battery voltage range
 
 10.0 - 15.5 VDC
 
 
 Charge control
 
 3 stage with manual equalize
 
 
 Charge temperature compensation
 
 Remote battery sensor (included)
 
 
 Efficiency
 
 85% typical
 
 
 AC input power factor
 
 0.95
 
 
 Input current (for 150 A charging)
 
 22 A RMS nominal
 
 
 AC input voltage
 
 120 VAC nominal
 
 
 AC input voltage range
 
 90 - 135 VAC
 
 
 Compatible battery types
 
 Wet/Gel/AGM
 
 
 General Specifications
 
 
 Operating temperature range
 
 -4F - 122F (-20C - 50C)
 
 
 Storage temperature range
 
 -40F - 122F (-40C - 50C)
 
 
 Dimensions (HxWxD)
 
 8.17 x 13.25 x 16" (208 x 336 x 406 mm)
 
 
 Weight
 
 75.0 lb (34.0 kg)
 
 
 Warranty
 
 3 years
 
 
 Part number
 
 809-3000 (Split phase in / Dual out)
 
 
 Accessories
 
 System Control Panel

Automatic Generator Start

 
 Regulatory Approvals
 CSA/NRTL certified to CSA 107.1, UL 458
 FCC Class B/Industry Canada Class
 

 
« Last Edit: June 30, 2007, 09:12:15 PM by Nick Badame Refrig. Co. » Logged

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« Reply #17 on: June 30, 2007, 09:03:48 PM »

Here's the 4024


SW2512MC & SW4024MC2
Widely used throughout the world as a primary source of AC electricity, the SW offers sine wave, utility grade output power, high capacity battery charger, high surge current ability (inrush current), and easy installation.


 
   
 Product Info | Specifications | Document Downloads | Compare 
 
 Specifications Available
SW2512MC
SW4024MC2


SW2512MC

 
 Electrical Specifications
 
 
 AC input voltage
 
 120 VAC
 
 
 AC input voltage range
 
 80 - 149 VAC
 
 
 AC input current
 
 60 amps AC pass thru 30 amps AC charging (Required for full pass through and full charging)
 
 
 Continuous Power @ 25C
 
 2500 VA
 
 
 Efficiency (Peak)
 
 90%
 
 
 AC output voltage (RMS)
 
 120 VAC
 
 
 AC output voltage regulation
 
 +/- 5%
 
 
 Frequency
 
 60 Hz
 
 
 Waveform
 
 Sine wave, 34 - 52 steps per cycle
 
 
 Total harmonic distortion
 
 < 5%
 
 
 Continuous output @ 25C
 
 21 amps AC
 
 
 Surge capability:
 
 
 
 
 5 sec rating (resistive)
 
 4000 watts
 
 
 1 mSec
 
 65 amps AC
 
 
 100 mSec
 
 46 amps AC
 
 
 Automatic transfer relay
 
 60 amps
 
 
 DC input voltage (Nominal)
 
 12 VDC
 
 
 DC input voltage range
 
 11.8 - 16.5 VDC
 
 
 DC current at rated power
 
 275 amps
 
 
 Idle consumption
 
 < 16 watts Typical at Full Voltage
 
 
 Search mode consumption
 
 < 1 watt
 
 
 Max. charge rate (adjustable)
 
 150 amps DC at 12 V nom.
 
 
 General Specifications
 
 
 Specified temperature range
 
 32F - 77F (0C - 25C) Power derated about 25C
 
 
 Enclosure type
 
 Indoor, ventilated, steel chassis with powdercoat finish
 
 
 Unit weight
 
 90 lb (41 kg)
 
 
 Shipping
 
 96 lb (45 kg)
 
 
 Inverter dimensions (H x W x D)
 
 15 x 22.5 x 9" (38 x 57 x 23 cm)
 
 
 Shipping dimensions (H x W x D)
 
 15 x 27 x 21" (38 x 69 x 53 cm)
 
 
 Mounting
 
 Bulkhead mount
 
 
 Warranty
 
 Two years
 
 
 Part numbers
 
 SW2512MC
 
 
 
 
 SW4024MC2
 
 
 
 
 SWRC (SW remote control panel with LCD and 25' cable for SW4024MC2 and SW2512MC)
 
 
 
 
 SWRC/50FT (same as above but with 50' cable)
 
 
 Regulatory Approvals
 
 
 cETL approved to UL 1741, UL 458, and CSA 107.1
 



SW4024MC2

 
 Electrical Specifications
 
 
 AC input voltage
 
 120 VAC
 
 
 AC input voltage range
 
 80 - 149 VAC
 
 
 AC input current
 
 60 amps AC pass thru 30 amps AC charging (Required for full pass through and full charging)
 
 
 Continuous Power @ 25C
 
 4000 VA
 
 
 Efficiency (Peak)
 
 94%
 
 
 AC output voltage (RMS)
 
 120 VAC
 
 
 AC output voltage regulation
 
 +/- 5%
 
 
 Frequency
 
 60 Hz
 
 
 Waveform
 
 Sine wave, 34 - 52 steps per cycle
 
 
 Total harmonic distortion
 
 < 5%
 
 
 Continuous output @ 25C
 
 33 amps AC
 
 
 Surge capability:
 
 
 
 
 5 sec rating (resistive)
 
 8000 watts
 
 
 1 mSec
 
 110 amps AC
 
 
 100 mSec
 
 78 amps AC
 
 
 Automatic transfer relay
 
 60 amps
 
 
 DC input voltage (Nominal)
 
 24 VDC
 
 
 DC input voltage range
 
 22 - 33 VDC
 
 
 DC current at rated power
 
 200 amps DC
 
 
 Idle consumption
 
 < 16 watts Typical at Full Voltage
 
 
 Search mode consumption
 
 < 1 watt
 
 
 Max. charge rate (adjustable)
 
 120 amps DC at 24 V nom.
 
 
 General Specifications
 
 
 Specified temperature range
 
 32F - 77F (0C - 25C) Power derated about 25C
 
 
 Enclosure type
 
 Indoor, ventilated, steel chassis with powdercoat finish
 
 
 Unit weight
 
 105 lb (48 kg)
 
 
 Shipping
 
 111 lb (50 kg)
 
 
 Inverter dimensions (H x W x D)
 
 15 x 22.5 x 9" (38 x 57 x 23 cm)
 
 
 Shipping dimensions (H x W x D)
 
 15 x 27 x 21" (38 x 69 x 53 cm)
 
 
 Mounting
 
 Bulkhead mount
 
 
 Warranty
 
 Two years
 
 
 Part numbers
 
 SW2512MC
 
 
 
 
 SW4024MC2
 
 
 
 
 SWRC (SW remote control panel with LCD and 25' cable for SW4024MC2 and SW2512MC)
 
 
 
 
 SWRC/50FT (same as above but with 50' cable)
 
 
 Regulatory Approvals
 
 
 ETL approved under standard UL458
 



 
« Last Edit: June 30, 2007, 09:20:20 PM by Nick Badame Refrig. Co. » Logged

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« Reply #18 on: June 30, 2007, 09:10:33 PM »

Magnum/Outback don't let you copy/print their specs so, here is the link
Nick-


http://www.magnumteknologies.com/
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« Reply #19 on: June 30, 2007, 09:32:02 PM »

In dealing with alot of refrigeration compressors, ... when voltage drops, why does the amp draw increase.
...
How do theese motors know to try and keep a certain rpm?


Nick,

There are two basic types of AC motors (OK, I know electrical-engineer types can dispute this, as there are many variations on these today).

The first type, which is common in, for example, electric drills, is called a universal motor and is wound just like a DC motor, with slip-rings and commutators.  These motors behave more or less like a resistive load -- if you reduce the voltage, you will reduce the power and speed of the motor.  The advantage is that it is easy to control the speed, as it is a direct function of voltage, and it's not sensitive to line frequency.  Also, it can be used on AC or DC.

The second major type is the synchronous motor.  This motor will turn at a speed that is a direct function of the AC line frequency.  Almost all three-phase motors are synchronous, and it is very easy to build a synchronous motor when you have three phases available.  Basically, the motor has three (or multiples thereof) windings that are offset from each other by 120 degrees, and as each phase voltage peaks in its respective winding it will attract the corresponding pole of the rotor (overly simplistic, but that's the basic idea).

A single-phase synchronous motor presents special challenges.  Something must be done to create a "phase offset" to set up a moving magnetic field for the rotor to follow in order to get the rotor moving.  There are several techniques... low torque motors such as table fans use what is known as a "shaded pole" and high torque motors such as your compressors generally use a technique involving a start-up winding called "split phase."  The start-up winding gets cut out of the circuit once the motor has reached synchronous speed by a centrifugal switch.  Starting torque can be increased and/or starting current reduced in a split-phase motor through use of a "start  capacitor".

In any case, one thing all synchronous motors have in common is that once running, the nature of electromagnetic force causes the motor to resist any force that would cause the rotor to fall out of synch with the AC current frequency.  The further out of synch you try to push the rotor, the greater the motor will try to resist, and the current in the windings will increase to achieve this.

Any load on the motor is a force trying to drag the rotor out of synch, so current in the windings will increase to compensate.  And, as we discussed, if the load on the motor is constant, and the AC frequency is constant, but the voltage drops, then current will also increase to compensate.

Here are a couple of sites that go into much more detail on how AC motors work:
http://www.coolmagnetman.com/magacmot.htm
http://en.wikipedia.org/wiki/AC_motor

Incidentally, one thing that helps tremendously in a situation where you need to run an A/C on perhaps marginal park power, is to use a bigger cord.  Every wire has a voltage drop across it that is related to length, but larger gauges have less drop.  So when we are someplace where we have access only to, for example, a 15-amp circuit, but we need to run one A/C (running load of about 13 amps, once started), we forgo our 50', 10-gauge shore cord and haul out the big guns -- our 25' 6-gauge shore cord, with a dogbone on the end to connect to the 15-amp outlet.  If we need more length, we add our 40' 6-gauge extension cord.  Even though it's only carrying 15 amps, having the 6-gauge really cuts down on the voltage drop.

-Sean
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« Reply #20 on: June 30, 2007, 09:35:28 PM »

Magnum/Outback don't let you copy/print their specs so, here is the link

http://http://www.magnumteknologies.com/


Actually, that's (confusingly) a different "Magnum."  Who also sells inverters, but not the sine-wave model we have been discussing.  The correct link is:

http://www.magnumenergy.com

-Sean
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« Reply #21 on: July 01, 2007, 09:43:10 AM »

I am just moving this topic to the top so I do not lose it. I am going to have to take exception to Shawn's description of motors and I want to really think about it long and hard before I do so. LOL
Richrd

Magnum/Outback don't let you copy/print their specs so, here is the link

http://http://www.magnumteknologies.com/


Actually, that's (confusingly) a different "Magnum."  Who also sells inverters, but not the sine-wave model we have been discussing.  The correct link is:

http://http://www.magnumenergy.com

-Sean
http://http://OurOdyssey.BlogSpot.com

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« Reply #22 on: July 01, 2007, 10:02:30 AM »

I am just moving this topic to the top so I do not lose it. I am going to have to take exception to Shawn's description of motors and I want to really think about it long and hard before I do so. LOL


See, I told you the electrical-engineer types would dispute it  Smiley

Richard, I did say that I was glossing over a lot of stuff...  I did not want to launch into a full-scale discussion of inductance, reluctance, magnetic flux, and the phase of the moon  Grin.  Which is why I put the links in to basic motor technology sites.

But if I really got something wrong (as opposed to just really oversimplified), do let me know....

-Sean
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« Reply #23 on: July 01, 2007, 12:44:23 PM »

I am just moving this topic to the top so I do not lose it. I am going to have to take exception to Shawn's description of motors and I want to really think about it long and hard before I do so. LOL
Richrd

Magnum/Outback don't let you copy/print their specs so, here is the link

http://http://www.magnumteknologies.com/


Actually, that's (confusingly) a different "Magnum."  Who also sells inverters, but not the sine-wave model we have been discussing.  The correct link is:

http://http://www.magnumenergy.com

-Sean
http://http://OurOdyssey.BlogSpot.com


Couldn't ya look at how his name is spelled correctly while ya contemplating picking his post apart!
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« Reply #24 on: July 01, 2007, 02:37:53 PM »

Hi Sean,

Thanks for all the information.

I'm a little more clear on the split phase and shaded pole motors now...  Maybe thats why I find terminals burnt up on compressors

that have either locked rotar or lost it's start windings. I'm gonna read thoose links you posted some more.

Thanks Again
Nick-

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« Reply #25 on: July 01, 2007, 05:32:44 PM »

I also advise to use adequate wire size but your example is a little extreme. Using the calculator on this link, shows a voltage drop of .66 volts on 50' of #10 at 13 amps. I don't think this will have significant effect on motor current.

http://www.stealth316.com/2-wire-resistance.htm
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« Reply #26 on: July 01, 2007, 06:04:25 PM »

I am just moving this topic to the top so I do not lose it. I am going to have to take exception to Shawn's description of motors and I want to really think about it long and hard before I do so. LOL
Richrd

Magnum/Outback don't let you copy/print their specs so, here is the link

http://http://www.magnumteknologies.com/


Actually, that's (confusingly) a different "Magnum."  Who also sells inverters, but not the sine-wave model we have been discussing.  The correct link is:

http://http://www.magnumenergy.com

-Sean
http://http://OurOdyssey.BlogSpot.com


Couldn't ya look at how his name is spelled correctly while ya contemplating picking his post apart!


If you look close BK, you will note that I misspelled my name also. Since today is my 52nd wedding anniversary I will blame the errors on that. LOL
Richard
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« Reply #27 on: July 01, 2007, 09:53:53 PM »

...your example is a little extreme. Using the calculator on this link, shows a voltage drop of .66 volts on 50' of #10 at 13 amps...
http://http://www.stealth316.com/2-wire-resistance.htm


Umm, I think the calculator on that link is for 12VDC.  That's not the right formula for 120VAC.  Also, while the A/C has a running load of 13A, the coach will be drawing 15A, the rated capacity of the circuit.  When I run the numbers, I get a drop of 1.6%.

That is within acceptable tolerance, however, I was talking about a situation where the park voltage was marginal to begin with.  So if you had only, say, 110 volts at the pedestal, now you'll have 108 (or maybe much, much less -- see below).  You are right, that won't have too much effect on compressor running current (an extra .2 amp from the draw at the nominal rating of 120 volts), but it is, in my experience, a noticeable difference.  And, with only ~2 amps left over to run everything in the coach, including the battery charger, that .2 amp represents 10% of the available capacity.

By contrast, 25' of 6-gauge is a drop of only 0.3%, less than a fifth the drop of my 10-gauge cord.

The numbers get much more definitive at higher currents.  I can use the 10-gauge cord set on a 30-amp circuit as well, and I often do (although I also often dial the draw back down to 20 amps).  At a 30-amp draw, the drop on 50' of #10 rises to 3.1%, considered just out of the acceptable range.  If I have a solid 120VAC at the pole, I don't worry too much that I'll be getting only 116 in the coach.  But if I have only 110 coming in, that will drop to 106.6, again a noticeable difference.

Remember, also, that voltage drop is current dependent.  So when you take your (almost zero current) DVM to the pedestal and measure, say, 115VAC, you may not realize that the 30-A circuit on that pedestal runs back to the main panel on perhaps 100' or more of #10.  So now my 50' cord is making a run of 150' on #10 wire, for a whopping 9.3% voltage drop (104 volts at the coach) on a 30-amp draw, or 4.7% on a 15-amp draw (109.6 volts).  There is not much you can do about the gauge and length of the wire from the main to the pedestal, but you can at least minimize the additional drop in your additional cord.

YMMV.

-Sean
http://OurOdyssey.BlogSpot.com
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« Reply #28 on: July 02, 2007, 07:28:57 PM »

Sean and all, In my experience, the majority of motors (excluding the hand tool motors) are asynchronous as opposed to synchronous.

Three phase Synchronous motors are designed to run at a specific speed (rpm) regardless of input voltage or the connected load, as long as these items are within the operating parameters of the motor.

For example, a four pole synchronous motor, connected to a 60 hertz power source will rotate at exactly 1800 rpm +-0 from no load to full load. Typically it will stay locked in up to 150% load and with input voltage varying as much as 20% or more. With a properly adjusted exciter, the power factor will be 1.0 pf. This means that every amp going into the motor is being converted to watts. If the excitation is increased the pf will go leading and the motor will began acting as a synchronous condenser and this phenomenon is utilized by many large companies to try and correct their normal lagging power factor, since the utility company penalizes companies for having a poor (lagging) power factor.

In my experience, less than 1% of all the 3 phase motors in existence are of the synchronous type. In fact they were so scarce that in the 70s I had to develop (invent) a method of converting a synchronous alternator into a synchronous motor in order to have a supply of motors to build the power converters I was manufacturing for the main frame computer market place.

Many years ago these motors were used in large conveyor systems to maintain  the synchronous speed of various production lines but I believe the advent of the easily controlled Variable Frequency Drive Systems driving asynchronous motors  have replaced  the synchronous motor.

The only other place that I am aware of this type motor being used is in the electric wall clock. Did anyone ever wonder why they keep such accurate time?

It is because the driving motor is a synchronous motor which is locked to the frequency of the utility power grid it is connected to.  Additionally the entire power grid in the US is tied together so that phase A of the power in California is exactly in step with phase A in Maine.

Even further, the grid is so regulated that every night just before midnight the overall US grid is tweaked up or down, as necessary to make sure that the correct  number of cycles have occurred within the past twenty four hours. And that boys and girls is why our wall clocks are so accurate. 

The asynchronous motor is the workhorse of the industrial world and is more commonly referred to as an induction or squirrel cage motor. Its RPM is always less than the synchronous speed would be.

For example, a four pole induction motor, connected to a 60 hertz power line will operate at approximately 1790 rpm at no load and 1750 rpm at full load. The actual rpm depends on the quality of the motor and the design. Some are designed to be low slip, and some are designed to be high slip.

I could probably continue on for many pages, but have tried to limit this to the minimum that would get my opinion across.
Richard
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« Reply #29 on: July 03, 2007, 03:01:30 PM »

Richard,

My brain must be addled -- of course you are right, I left out the third and most common type of AC motor, the induction motor.  And, of course, the compressor motors Nick was asking about are likely induction motors.  Always good to have a real heavy-duty-power guy around to set me straight.

The answer about the current is still the same -- any effort to resist the magnetic force trying to pull the rotor forward will be met with increased current in the windings.

Squirrel-cage rotors are also one of the possible mechanisms for starting synchronous motors until they reach synchronous speed.

-Sean
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« Reply #30 on: July 03, 2007, 05:13:00 PM »

Sean, (see I can spell it right) I think you are absolutely correct. There is so much information available about any given subject and it is extremely easy to overlook something, especially when posting to a board. These items would not be missed during a personal conversation. I strongly suspect that either of us could produce pages of information about motors, but very few people would be interested, so we try and hit the high points. Unfortunately we sometimes miss one of the points, and I think that is exactly what happened to you. That is why I was so hesitant in calling it to your attention as I did not want to create any hard feelings. Hopefully out of all of this all of us have learned a little more and I believe Nick's question got answered.
Richard
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