Inverters for submersible pumps.

highway-equipment

I watched a video on power bright inverters that said they were different than other modified sine wave inverters and that they can run inductive loads. What are your ideas on that? Is it all hype or designed differently? I also wondered if anyone had seen or used the Samlex 3024 inverter charger.

http://www.powerbright.com/video.html

http://www.samlexamerica.com/products/productdescription.asp?ProductsID=17840

BB.

Re: Inverters for submersible pumps.

If you have not yet read the inverter faqs--you should take a look at them now:

All About Inverters
Choosing an inverter for water pumping

The video is playing fast and loose with the facts... There may very well be MSW inverters that don't like inductive loads--but there are plenty out there that will drive inductive loads just fine. And they started an unloaded compressor--much easier to do than starting one with 100+ PSI in the tank.

The bigger issue is that they don't "fix" the problem with MSW (Modified Square/Sine Wave) inverters where the MSW wave form can cause motors and other devices to draw upwards of 20% additional power because of the square wave shape of the AC power--which is wasted as heat in the devices loads.

And some of these devices (maybe 10-20%) will have early failures because of the MSW wave form.

I have no idea about the company or their products... If you like them and/or their price--go ahead... If, however, you are expecting TSW (true sine wave) performance from an MSW inverter--not going to happen.

-Bill

highway-equipment

Re: Inverters for submersible pumps.

Thanks I had tried to read the one for inverters for pumps but it will not load for me. The info on inverters tells alot. The samlex said it was new and was sine wave. I was trying to find something for a camp I am building. It is not going to be continuous use but I dont want to skimp and burn up something right out of the gate. Thanks again

BB.

Re: Inverters for submersible pumps.

The second link still loads OK for me...

If you have a PC, try right mouse clicking and click on "Save Link As" and see if you can download the PDF, then open the file. It is a nice article from Home Power Magazine.

-Bill

highway-equipment

Re: Inverters for submersible pumps.

Thanks that worked and it was a good article

blackswan555

Re: Inverters for submersible pumps.

Also keep in mind that with those type of pumps, the longer and thinner it is the more the peak start up load will be, 10 times its run load on some of them,
Think short spanner to turn bolt or long spanner, long takes a lot less force, small vs larger diameter rotor, less amps to start larger, (LRA locked rotor amps)

Have a good one
Tim

highway-equipment

Re: Inverters for submersible pumps.

thanks for the info

GreenPowerManiac

Re: Inverters for submersible pumps.

What does the pump draw in current when starting ? & what is your battery/electric source(s) ?

By saying inductive loads, are you referring to a "Soft Start" ?

The PDF file was an interesting read, however, there was one issue left out. This is coming from an expert electrician, not myself. The file describes a heat increase from using MSW inverters. Could be called a Pulse Inverter. What happens are the pulses that go into a pump have to be converted to Pure Sine Wave for it to work. The pump can't tell the difference. The extra heat is created by conversion into PSW. The pump windings naturally convert it for use, as with many larger electrical motors. This is that (whining) wind up & down sound we hear when CNC machinery spins a tool up to speed.

Sounds like to me that your load is too great for the inverter to handle. Depending on the size of the pump, could be drawing too much on start up. If the wires have not burned up or get hot when you try to start the pump, then they're good and properly sized. If the inverter is stopping the start up, it can't take the load.

Example: I have a 5hp air compressor in my Garage. When turned on, it'll draw too much current and the 4500 watt inverter shuts down the system. The compressor will try to start, however, fails then the lights go out.

Cariboocoot

Re: Inverters for submersible pumps.

GreenPowerManiac wrote: »

Example: I have a 5hp air compressor in my Garage. When turned on, it'll draw too much current and the 4500 watt inverter shuts down the system. The compressor will try to start, however, fails then the lights go out.

This is not surprising, as 5 electrical horsepower is 3730 Watts. The start-up draw of a motor that size would be way over the inverter's 4500 rating, especially if it's having to start against a partially pressurized tank of air (extra resistance).

Never rely on an inverter's "surge rating" for anything. If you want to be able to run big loads like that and don't know the exact start-up current, the best plan is to rate the inverter for the "outlet" (at least to begin with). In other words, something that's meant to be connected to a 30 Amp/240 VAC outlet should work off a 8kW inverter. Ooh, not so easy to get, eh? That's the problem.

Never run any equipment 'close to the limit' - either high or low - whether it be in terms of Voltage, Amperage, Wattage, or temperature.

BB.

Re: Inverters for submersible pumps.

GreenPowerManiac wrote: »

By saying inductive loads, are you referring to a "Soft Start" ?

Soft Start is just anything that limits the inrush current when a device is turned on... That that can be anything from a NTC Resistor (cold, high resistance; hot, low resistance) to "undersized/small" starting caps, etc...

The PDF file was an interesting read, however, there was one issue left out. This is coming from an expert electrician, not myself. The file describes a heat increase from using MSW inverters. Could be called a Pulse Inverter. What happens are the pulses that go into a pump have to be converted to Pure Sine Wave for it to work. The pump can't tell the difference. The extra heat is created by conversion into PSW. The pump windings naturally convert it for use, as with many larger electrical motors. This is that (whining) wind up & down sound we hear when CNC machinery spins a tool up to speed.

The MSW inverter output is very close to a square wave--you can call it a pulse train (there may be a delay from the "negative" to "positive" transmission--so it is not a "pure" square wave either).

There is no "conversion" of MSW into PSW inside the motor... At best, if you want to look at it this way--a "Square Wave" is really a bunch of overlapping sine wave with the 60 Hz fundamental and a bunch more higher frequency sine waves that, when all added together, look like a "square wave"... Look for websites about Fourier Series and Transforms (waring--very heavy duty math).

Only the fundamental frequency Sine Wave of 60Hz does any work... All of the rest go through the motor windings, creating changing changing magnetic fields in the windings and steel of the motor, etc... But--since these higher frequencies are not used to "turn the motor"--this extra energy (~20% of the power in the MSW spectrum) has to go somewhere--and that is wasted heat (pretty much ends up as I^2*R losses).

Regarding the "whine" you hear when a CNC (Computer Numerically Controlled) machine--You are hearing two effects... One is the (typical) "cogging action" that DC "Stepper/brushless" motors tend to have (motion is not a smooth rotation, but a series of steps).

The second is that the "driver circuity" for these DC drives is a variable speed inverter... Basically, the inverter starts at low frequency (motor stopped, starting rotation) then increases the frequency as the motor increases to final speed. If you output the final frequency (operating speed) right from the start--the motor would just sit there an buzz--the controller/inverter needs to stay in sync with the DC motor to bring it up to speed. When the "step pulses" are out of sync with the motor, there is no torque developed (big difference between "synchronous" motors and and non-synchronous motors like Induction Motors).

Has nothing to do with a normal "induction" motor coming up to speed on a pump. (wiki on various types of motors)

Induction motors work by first creating a "rotating field" (commonly a main winding and a starting winding that is offset physically and electrically--by a series capacitor--needed for single phase power). The center part of the induction motor is just a bunch of laminated steel. When placed in a rotating field, the changing magnetic orientation causes electricity to flow inside the rotor. This electrical current creates a North/South magnetic pole that is then "dragged" around by the rotating field created by the Stator. Induction motors always spin slower than the rotating magnetic field (i.e., 1,750 RPM vs 1,800 RPM) because they need the "slip" to keep the North/South field in the rotor energized. If the rotor and the field went at the same speed, there is no magnetic change in the rotor, no current flow, no N/S field generated, nothing to "drag" to generate torque.

The harmonics of a MSW inverter are not "in phase" with the rotation of the motor. Also, the only noise that a MSW inverter may create in motors/devices that a PSW may not--Is that the "shape" edge of the MSW wave form is an "Impulse" like kick to the device. This edge has a wide range of frequencies (from fundamental on up). Typically devices are designed so that the 60 Hz fundamental does not case noise (who wants their home full of 120 Hz buzz--old florescent fixtures are bad enough). However the higher frequencies can cause other components in the device to buzz.

-Bill