12v dc water pump connection

Thread Starter

Joshfourie

Joined Nov 21, 2020
4
Hi am trying to connect a 12v dc water pump to 220v power supply though a AC220v/DC12v 150w inverter. The pump was working but with a clear rhythmic tempo and not continuous. I checked pump with a 12v battery and it works perfectly and pumps strong and continuous . I checked the inverter and it states for led only. Clearly the LED part that causes the issue but not sure why. Could someone explain?
 

Tonyr1084

Joined Sep 24, 2015
5,956
Welcome to AAC.

Your comment is a little confusing. An inverter is typically used to convert 12 volts DC to 110 or 220 volts AC. You can not put 220 VAC into an inverter and get 12 VDC out. Perhaps you've confused it with a power supply, which operates at 220 VAC input and has 12 VDC output. If your pump is surging then it's quite possible the power supply isn't strong enough to run the pump.

The supply will be rated by Input Voltage, Output Voltage and either Output Current or Output Wattage. If your motor needs (just as an example) 6 amps and your supply is rated for 5 amps then it's not strong enough to carry the load.

Please post a picture of what you have and how it's hooked up. The experts here will be able to direct you from there.
 

SamR

Joined Mar 19, 2019
3,399
It's likely a buck power supply and may be using cheaper switch mode instead of a more expensive transformer and the motor may be having problems with the chopped output. But without knowing exactly what you have... A model number or picture of the nameplate specs would help.
 

Tonyr1084

Joined Sep 24, 2015
5,956
1605990852113.png 1605990925372.png1605990744518.pngConstant Voltage for LED module only. My guess is that it can't handle the sudden inrush of current the motor needs. While 12.5 amps seems sufficient, a lot depends on how they're controlling the voltage in order to maintain the current. LED's are current controlled devices. Either they're controlled by a constant current or they're controlled by a resistor limiting the amount of current they draw. When you change the load (resistance or inductance) the voltage has to change to keep a constant current OR the current is changed to keep a constant voltage.

You may be better served by getting a different power supply. Or build one. A simple transformer of sufficient capacity and either a single diode or a full wave bridge rectifier to power the motor.
 

SamR

Joined Mar 19, 2019
3,399
Couldn't find a schematic for it but with 200mV of ripple and the "for LED us only" presumably it is a Switch Mode Power Supply. Doesn't have an inrush stat but it does say that it has "hiccup-mode recovery" from short circuit and overvoltage. This is probably why the motor is surging. Also, the 150W rating on chinesium devices is probably wishful thinking on their part.
 

Thread Starter

Joshfourie

Joined Nov 21, 2020
4
Looking for a 150w 12vDc rated output power power supply with ip67 rating as the pump is outside and so will the power supply be. The only damn thing I can find is for led. Might be better to build one? Anyone have schematics on this?
 

Thread Starter

Joshfourie

Joined Nov 21, 2020
4
Couldn't find a schematic for it but with 200mV of ripple and the "for LED us only" presumably it is a Switch Mode Power Supply. Doesn't have an inrush stat but it does say that it has "hiccup-mode recovery" from short circuit and overvoltage. This is probably why the motor is surging. Also, the 150W rating on chinesium devices is probably wishful thinking on their part.
Thanks, the power supply ran the motor once on the first test perfectly. Then when I connected all the wires more permanently and tested it gave this intermittent activity. Very strange but it is obvious it is not going to suffice. Could lowering water inlet head affect the start amps and then it will run better?
 

Tonyr1084

Joined Sep 24, 2015
5,956
Either of these should work as long as the transformer is of sufficient rating for the motor. I would advise the transformer be 1.3 times to 1.5 times the motor stall current rating. Twice the current rating is overkill and wasted space. The diodes will also need to be of sufficient size to handle the current (wattage). Too small a diode and it will burn up.
1606061302249.png
 

Qualflow

Joined Aug 12, 2020
1
Thanks, the power supply ran the motor once on the first test perfectly. Then when I connected all the wires more permanently and tested it gave this intermittent activity. Very strange but it is obvious it is not going to suffice. Could lowering water inlet head affect the start amps and then it will run better?
As others have said your going to need a bigger power supply. Typically with these LED supplies they don't have enough ballast to deal with inductive loads so you need to allow a lot of overhead when sizing them for this type of motor and the type of start stop loads it puts on the supply. These type of power supplies also typically have an over current protection that will derate the voltage and then shut off (short circuit protection/tick mode) if the load goes above the limits set on the power supply. The inrush will also be different if there is any back pressure/head of water when the pump is turned on (it takes longer to spin up). This type of pump is switched on/off with a pressure activated switch and usually this is the thing that goes at high currents after any prolonged use due to arcing at turn off.
You are usually better going for the 24V ones for that reason. Another thing to note is that this is a diaphragm pump so it what is classified as a positive displacement pump. It is possible to stall the motor if the pump switch isn't set correctly.

From experience you should typically have something with at least 50% overhead when using a LED power supply in this application. So for your pump you would want to go for something at least 200W. Be wary of cheap LED power supplies as some of them have horrible amounts of ripple on them.

Meanwell do a range of IP66/67 LED power supplies that we have used on bigger pumps that this (MWH series I think) though we usually go for the larger 350W one on a nominally 150W motor (there isn't anything smaller that is suitable).
 

Subpilot

Joined Feb 26, 2020
1
I want to just add that this may be a plumbing rather than electrical issue. RV water systems often oscillate and the cure is to add a pressure accumulator in line to dampen the pressure spikes. This will also reduce the peak current as the pump will not be dead headed. It is a very worthwhile upgrade and will reduce the annoying pump racket overall.
 
The term "inverter" is something that has been incorrectly utilized after the technology changed from CCFL (thin fluorescent tubes) to LED backlights for the flat-panel LCD displays used in HDTVs.
Originally these LCD TVs used high-voltage AC from the inverters to strike and control these CCFL backlights. After they changed to LED strips the new current controlled DC supplies continued to be incorrectly called inverters. Many have adopted this terminology when it comes to driving LEDs.
 
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