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Forum Index : Solar : soft starting single phase motor
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| Godoh Guru  Joined: 26/09/2020 Location: AustraliaPosts: 620 |
I have just bought a new log splitter. It has a 2kw motor with a hydraulic pump attached. My inverters won't start the motor, so I am wondering if anyone here has experience with using soft starters on single phase motors. The motor is a capacitor motor so i am wondering if a soft starter will work on it. I have tried a 3kw Latronics inverter on it and it just goes out on overload straight away. My home made inverter with a 5kw board and home made transformer tries to start it but it will not get up to speed.It goes out on overcurrent too before the motor gets to full speed So I am thinking that a soft starter may help it get running. Or alternately maybe some sort of off loader valve on the hydraulic pump, if there is such a thing. Any help appreciated Pete |
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Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1225 |
Hi Pete, I haven't tried any of those cheap sort start modules myself, I had thought someone would have by now, be interesting to find out as its not that much to them. Would like to convert my block splitter to electric as well this like most others open-center systems always have oil flow so no much point adding any unloader valve. Closed-center systems are always under pressure, but oil does not flow until you activate a lever asking the system to perform, I have this on one tractor and in a PITA, when other parts of the tractor are open center valve.  Cheers Aaron Off The Grid |
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| Godoh Guru Joined: 26/09/2020 Location: AustraliaPosts: 620 |
Hi Aaron, thanks for the reply. I have ordered a cheap soft starter to see it that will work. I will see how that goes. My inverter has no problems with my air compressor but it is only 1600 watts from memory. So if the soft starter doesn't work I may have to go to a smaller motor. Cheers Pete |
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KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 2075 |
On the home made inverter, how did you calibrate over current trip? Is it possible that you may have OC set a tad low. Depending on the design and DC operating voltage, a 5kW inverter with transformer output should start a 2kW motor. NANO:Inverter V 8.2ks - Linux AvrDude GUI script V4.0 |
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| Godoh Guru Joined: 26/09/2020 Location: AustraliaPosts: 620 |
Hi KeepIS. The home made inverter has an aliexpress board, there is a current adjustment but it is one of those multi turn pots. It has no instructions on how to calibrate it at all. I have set the voltage settings by adjusting the pots while using a benchtop power supply, so the high and low voltage settings work fine. But current adjustment doesn't really seem to do much. The aliexpress board is a 5kw board, it runs my other stuff fine. But with the new splitter it just spits the dummy. Honestly I have no ideas on how to load the inverter up to set current settings, I don't have a big enough dummy load to use. My battery bank is a 24 volt 660 ampere hour VRLA bank. Pete |
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| KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 2075 |
The current settings don't appear to do much because of the limited adjustment range some of these inverters have, it mainly changes the upper trip limit. Running at 24 volts DC places a higher limit on how much short-term peak current the FETS can handle, so in this case, I think it best to just let sleeping dogs lie. It was just a thought, wish I could be of more help. Mike. NANO:Inverter V 8.2ks - Linux AvrDude GUI script V4.0 |
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phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 3083 |
If the soft-starter is a 2 wire type it is best to wire it in series with the motor main winding only. You want full volts across the start winding and its series capacitor to get enough phase shift for the required starting torque. The capacitor limits the start current in that winding to little more than its normal running current. If the soft-starter is only wired in the supply to the motor there may not be enough starting torque to turn it at all. |
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Bryan1 Guru Joined: 22/02/2006 Location: AustraliaPosts: 1779 |
G'Day Pete I do have a couple of soft starters here and below is a picture of one   Regards Bryan |
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| Godoh Guru Joined: 26/09/2020 Location: AustraliaPosts: 620 |
Thanks phil, I will have a look at the motor tomorrow. I think it only has one capacitor, so it must stay in circuit all the time. Sounds like a good plan to put the starter only in with the run winding. Bryan have you tried using one of those starters you have? That looks like it is for an air conditioner. I can't quite figure out what they are doing with that starter, but it looks like they are switching the start winding out of circuit after it starts. Doesn't quite make sense to call the capacitor the run capacitor in that case. Most motors with only one capacitor and no starting switch just leave the cap and start winding in circuit all the time. Thanks for the input Mike. I have ordered a two wire soft starter, and will give it a try wired into the run winding only. I did think that I may be able to use a drill and run the motor up to speed a bit then hit the start button. I may try that tomorrow. Once it gets going the inverter should have no problems, I hope. Thanks Pete |
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| Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1225 |
A changed the air compressor over too electric a month or 2 a go, it had a 8Hp ICE on it now 2Hp Electric motor 1400RPM and it has centrifugal start and 1 capacitor, with the start switch its 36A starting, when the switch failed and rotor locked I measured about 30A, the inverter in the shed starts this motor on the Air compressor quite well, even turned it off just before full pressure then back on again, it will pull a lot from the 48v battery banks, (a few old 4WD FLA batts and some old (secondhand) used and abused 200Ah LiFePO4) The other motor I might use for the block splitter is 2.2Kw 2900Rpm (capacitor start no centrifugal switch) but much easier to start, compared to the lower power motor on the compressor. Pete, Do you have a clamp meter with inrush measurement? It would be nice to find how much difference it makes using a soft starter, on the other hand if the motor starts and runs after putting in the soft starter, well that's good enough.  Yep done that a few times with some rewired 3phase motors. Edited 2026-03-19 19:23 by Revlac Cheers Aaron Off The Grid |
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| Godoh Guru Joined: 26/09/2020 Location: AustraliaPosts: 620 |
Hi Aaron, I have a clamp meter, I don't think it does instantaneous measurements, but I do have an old analog one that I can check the inrush current with. I will have a look at what the motor is drawing. Good to know that you have used the drill method, I also have an air gun that I could use, so may try that as it has heaps more torque. The motor on the splitter is a 2 pole jobby too, 2800rpm. I have to go to town today but will play about this afternoon and see if I can get some measurements. cheers Pete |
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