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Will a soft starter help in reducing thehigh initial current in a Pump??

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  • Will a soft starter help in reducing thehigh initial current in a Pump??

    I am new to the solar industry and have got a assignment to run a AC pump of 1hp at 230V and 3.2A power of 750Watts without using any batteries,I have no idea if it is possible but have started designing it.I am stuck at a point where the initial current required by the motor is very high (upto 15A) i have been searching for alternatives that could reduce the surge and came across Soft starters. Since I am from a Electronics & Telecommunications background and a Undergraduate I don't know much about these soft starters but from what i have read on internet I find that it could serve my purpose. I require your views about the idea and also suggest me if there is any other alternatives that could suffice my need. I am completely open for suggestions. Thank you in advance.

  • #2
    Welcome onBoard

    What about this one:
    Originally posted by Mike90250 View Post
    The other thing that can be done, is to use a Linear Current Booster, which is designed to power a motor directly from PV, and overcome the problems of motor stalling
    http://www.solarpaneltalk.com/showth...urrent+booster


    http://store.yahoo.com/wind-sun/7amplincurbo.html

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    • #3
      That is for DC motors.
      MSEE, PE

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      • #4
        Originally posted by seshu View Post
        I am new to the solar industry and have got a assignment to run a AC pump of 1hp at 230V and 3.2A power of 750Watts without using any batteries
        Just exactly how are you planning on doing that? You will have to use a battery inverter.
        MSEE, PE

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        • #5
          Originally posted by seshu View Post
          I am new to the solar industry and have got a assignment to run a AC pump of 1hp at 230V and 3.2A power of 750Watts without using any batteries,I have no idea if it is possible but have started designing it.......
          Well, the good news, is you appear to be motivated.

          The bad news, is there is no possible way to do this without batteries and /or about 2x the running power in panels.

          PV panels have highly variable output, and even the brief shadow of a sparrow flying overhead, will glitch
          the array output, and possibly stall the motor.

          If you want pure PV powered, you need to look at some of the Grunfos pumps, that have their own solar controller, and fancy DC pump motor.

          You will need to know the lift requirement for the water (how high you are pumping it) and the flow needed at that lift, to size the pump. And you may need an elevated storage tank, since you will have no pump action when you have no bright sun.

          The DC pumps & controllers are expensive, but so is a large array and a large 240VAC inverter & batteries.

          As for [B]1hp at 230V and 3.2A power of 750Watts[/B] That is a classroom figure. Real life, my 1/2 hp pump, draws 970Watts running. While on paper, it's true that 1 hp equals 750 watts, motors and pumps are not 100% efficient. If this is a "classroom assingment" the instructor has failed.
          Last edited by Mike90250; 12-31-2011, 01:36 PM.
          Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
          || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
          || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

          solar: http://tinyurl.com/LMR-Solar
          gen: http://tinyurl.com/LMR-Lister

          Comment


          • #6
            Originally posted by seshu View Post
            I am new to the solar industry and have got a assignment to run a AC pump of 1hp at 230V and 3.2A power of 750Watts without using any batteries,I have no idea if it is possible but have started designing it.I am stuck at a point where the initial current required by the motor is very high (upto 15A) i have been searching for alternatives that could reduce the surge and came across Soft starters. Since I am from a Electronics & Telecommunications background and a Undergraduate I don't know much about these soft starters but from what i have read on internet I find that it could serve my purpose. I require your views about the idea and also suggest me if there is any other alternatives that could suffice my need. I am completely open for suggestions. Thank you in advance.
            I have used the Magnatec soft start controllers on 3 phase motors. They work well and are reliable.
            The only softstart single phase controllers that I have seen are on the 120v ECM blower motors, the ECM controllers are mounted on the back of the motor.
            The only problem may be that the pump may not start at low power because of the resistance of the water on the impellers.
            Grundfoss makes a pump that can be used with 240 A/C or DC voltage.
            The inverter model well pumps have reliability issues with the controllers.

            Comment


            • #7
              Originally posted by Mike90250 View Post
              Well, the good news, is you appear to be motivated.

              The bad news, is there is no possible way to do this without batteries and /or about 2x the running power in panels.

              PV panels have highly variable output, and even the brief shadow of a sparrow flying overhead, will glitch
              the array output, and possibly stall the motor.

              If you want pure PV powered, you need to look at some of the Grunfos pumps, that have their own solar controller, and fancy DC pump motor.

              You will need to know the lift requirement for the water (how high you are pumping it) and the flow needed at that lift, to size the pump. And you may need an elevated storage tank, since you will have no pump action when you have no bright sun.

              The DC pumps & controllers are expensive, but so is a large array and a large 240VAC inverter & batteries.

              As for [B]1hp at 230V and 3.2A power of 750Watts[/B] That is a classroom figure. Real life, my 1/2 hp pump, draws 970Watts running. While on paper, it's true that 1 hp equals 750 watts, motors and pumps are not 100% efficient. If this is a "classroom assingment" the instructor has failed.
              Thank you Mike your post was really helpful. A cousin of mine gave me a different idea of using a Variable Frequency Drive in place of a soft starter which could ramp up the input power and he also told me that if i use a soft starter made of SCR's there are chances of the starter being heated up and breaking down.

              The idea to use a Grunfos pump is good but would be costly, as this design is for irrigation purpose and needs to be cost effective.

              Regarding the power requirement of the 1hp motor as you have pointed out the actual power requirement would be nearly about 25% more than the rated power and also the output power glitch of the PV modules is another issue to be addressed. Considering all the above what if i increase the number of PV modules and incorporate a set of batteries with a effective power of 1KW-1.5KW would the system survive or should i first check the power the motor draws and then go about the design?

              About the dimensions of the well, it is 25-30feet deep and the overhead tank is around 30feet high the motor manufacturer recommended a 1hp pump.Mike if u were in my position what would you recommend would you prefer to increase the number of PV modules or use controllers? which would be durable.

              Regarding the sunlight at the place I live, I minimum have a constant irradiation of about 5hours a day and would like to run the pump for an effective 3hours.

              P.S. I know I have a lot of doubts but I guess its more effective to learn by asking doubts.I really appreciate your help Thank You.

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              • #8
                You have some days with little sun during the monsoon season.
                [SIGPIC][/SIGPIC]

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                • #9
                  Originally posted by russ View Post
                  You have some days with little sun during the monsoon season.
                  Yes i live in southern part of India where more or less we have at least 2-3 hours of Sunlight even in monsoon overall i could say that we have sunlight for say 320 odd days a year.

                  Comment


                  • #10
                    Originally posted by LucMan View Post
                    I have used the Magnatec soft start controllers on 3 phase motors. They work well and are reliable.
                    The only softstart single phase controllers that I have seen are on the 120v ECM blower motors, the ECM controllers are mounted on the back of the motor.
                    The only problem may be that the pump may not start at low power because of the resistance of the water on the impellers.
                    Grundfoss makes a pump that can be used with 240 A/C or DC voltage.
                    The inverter model well pumps have reliability issues with the controllers.
                    Thanks for the information LucMan can you suggest me any idea where i can overcome the problem of not being able to start the pump at low power and do you thing if i use a variable frequency drive there wont be any reliability issues in the inverter problem.Thank you in advance.

                    Comment


                    • #11
                      It looks like you only need to pump 60 ft. How many GPM do you need ? A 1 HP 230v pump seems quite large for that distance.
                      Take a look at SunPumps or Shurflow pumps they are well suited to your application. No VFD or soft start required as they are DC pumps and can be run directly from batteries & PV panels.

                      Comment


                      • #12
                        [QUOTE=seshu;38302]...The idea to use a Grunfos pump is good but would be costly, as this design is for irrigation purpose and needs to be cost effective.
                        ...[QUOTE]

                        Solar, is [B]not [/B]going to be cost effective.

                        You need to list what the actual water pumping needs are, GPM - the more efficent the system can be made, the less the parts cost.

                        A cousin of mine gave me a different idea of using a Variable Frequency Drive in place of a soft starter which could ramp up the input power and he also told me that if i use a soft starter made of SCR's there are chances of the starter being heated up and breaking down.
                        A commercial "VFD" configured for slow start ramp up to rpm, shoudl work fine, they list if they have to be attached to a heat sink, or not. They only heat up during the starting phase, since you only have 1 start per day, it should not be much of an issue.

                        Another thing is to get an electrician, or buy your own, PEAK READING (or sometimes called Peak Hold) AC AMPMETER. You need to measure the motor starting current, with a special meter that can read the half second peak as the motor starts. The meters cost about $300 in the US.
                        Last edited by Mike90250; 01-03-2012, 02:22 PM.
                        Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                        || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                        || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                        solar: http://tinyurl.com/LMR-Solar
                        gen: http://tinyurl.com/LMR-Lister

                        Comment

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