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I have a plastic crusher with a three phase motor and I will like to operate it using single phase 220v.

Can anyone please help me out with instructions on how to connect it?

Also, I want to know if I will be using two capacitors? (start capacitor and a run capacitor)

Can I also know the exact capacitor(s) value which I will require?

I have attached a picture of the label of the motor, a picture of the motor contactor and a picture of the motor wiring.

Thanks in advance.

enter image description here enter image description here enter image description here

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  • \$\begingroup\$ Something is wrong with that label. Either the speed should be less than 1500r/min or the frequency should be 60Hz, but a motor that big should not have that much slip. The only countries I know of with 220V 60Hz are some of those South American countries with a mixture of American & European standards. If it is designed for 60Hz, the speed should be about 1750r/min \$\endgroup\$ Commented Dec 24, 2020 at 2:43

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If your budget allows it you should get a VFD (Variable Frequency Drive). It can create three phase signals with different phase shifts and frequencies, giving you the ability to cintrol speed, direction, power etc. of your motor. These can be found on eBay for moderate prices, the more powerful they are the more expensive. There are probably other options, but considering the 3 phases are kinda crucial for the motor to work, I don´t think you can just connect it to a single phase without some kind of motor controller.

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There are basically three approaches to running a 3-phase motor from single phase power. None of them is as convenient as buying a single phase motor in the first place.

  1. Static phase converter. This involves a bespoke arrangment of capacitors to shift the phase. Here is a commercial supplier. It does not give you full torque and has relatively low efficiency so I think it would be unsuitable for a crusher that has high peak loads. There are plenty of DIY approaches you can google if you like to tinker. There will be two run caps plus a starting cap. Image below is from this website, which has detailed info on how to calculate the capacitor values.

enter image description here

  1. Rotary phase converter. This involves running a (often larger) 3-phase idler motor as a kind of generator from the single phase power. Here is a commercial supplier. It's not as crazy as it sounds, as (used) 3-phase motors can often be purchased for close to scrap price. Again, there are plenty of DIY approaches you can google- this used to be the popular way of powering an industrial Bridgeport milling machine in a hobbyist's garage. Sometimes the motor is fitted with a proper starter, sometimes a rope on the (otherwise unloaded) motor shaft is used (sounds a bit dangerous to me). The schematic is similar to the static phase converter, except there's an idler motor in parallel with the motor and usually a starter contactor and timer.

  2. VFD (Variable Frequency Drive). This is a box that converts incoming power (single or three phase, depending on design) to DC and then uses IGBTs or MOSFETs to convert the DC back into 3-phase AC at variable frequency. This has the advantage that it allows you to change the motor RPM. They have dropped quite a bit in recent years, and very inexpensive ones are available from Asia. Above relatively low HP range they generally require 3-phase input power to get the DC. Your motor is about 7.5 HP, so if you go this way make sure you specify one that allows single-phase input power. Some will allow either single-phase or 3-phase input power but significantly derate the maximum HP when single phase is used. The electronics is too complex (and commercial products are relatively cheap) for DIY approaches to be practical. The schematic is just power in and power out, plus grounds.

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  • \$\begingroup\$ did anyone explain to the user this method 1,2 cannot economically supply 18.9A rated current per phase? I know I mentioned it. \$\endgroup\$ Commented Jul 5, 2019 at 17:31
  • \$\begingroup\$ OPTION 1 IS NOT RECOMMENDED FOR HEAVY CRUSHER APPLICATIONS DUE TO THE LOSS ED >50% OF NAMEPLATE HP. (1) Read your 1st link . Not only is a VFD very convenient 3 phase generator , it is practical for not exceeding breaker rating on startup. (-2) \$\endgroup\$ Commented Jul 7, 2019 at 10:53
  • \$\begingroup\$ Yeah, I already said that in the original answer. Probably the motor isn't generously sized either, knowing those guys. \$\endgroup\$ Commented Jul 7, 2019 at 10:55
  • \$\begingroup\$ I read not full torque . when < 50% is a way of saying do not use this method for heavy applicaitons \$\endgroup\$ Commented Jul 7, 2019 at 10:57
  • \$\begingroup\$ The cap labelled Caps L1-L3 will be trying to make it go forward. The starting cap and Caps L2-L3 will be trying to make it go in reverse. Remove L1-L3 and put them where it was. \$\endgroup\$ Commented Dec 24, 2020 at 2:31
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The old-fashioned alternative to a modern VFD, as mentioned in another answer, would be a "rotary inverter". A rotary inverter is really just an electric motor driving an alternator. Using a single phase motor and a three-phase alternator would give the required result.

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The motor is already connected in DELTA, so, if the name plate says 380V, it is now 220V. Connect the capacitor as shown. The value depends on the current drawn. The current through the capacitor will be less (about 1/2) on startup rather than more, so if you are starting it on load, you will need a larger capacitor while starting (maybe up to 10x). The torque characteristic won't be as good as on 3 Phase. Use the rated current at 220V on the nameplate as a guide to calculate the capacitor value, then you can adjust the value to make the current equal to the other phases. Use a capacitor rated for motor run use, or power factor correction capacitor(s). I don't know what combination of ratings that motor has. Even the manufacturer doesn't know. A motor rated at 50Hz doesn't go at 1680r/min & a 60Hz motor isn't normally rated at 220V (unless it's from South America somewhere). Also, a motor that size doesn't have that much slip. On 60Hz, it would run at about 1750r/min. enter image description here

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Due to the cost of matching PU plastic grid rated cap Impedances to motor impedances are greater than VFD, look only for the best match to your needs in current in a VFD solution. the costs in your range are ~< $10/A for 3 phase VFD’s. Up to $25/A. e.g. https://www.ato.com/single-phase-to-three-phase-vfd. Which is not to say it is a preferred source , but just an example of a good one.

THere are two individuals who have down-voted this correct answer. -2 are incorrect and silent. Readers be warned.

Static Capacitive PHase converters ARE NOT RECOMMENDED for HEAVY APPLICATIONS such as this PLASTIC CRUSHER. The reason is YOU ONLY GET < 50% of the NAMEPLATE HORSEPOWER. ANswers which suggest STATIC CONVERTERS for about the same PRice as a good VFD are thus NOT RECOMMENDED.

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  • \$\begingroup\$ Sorry you two -2, but I have experience in these matters. Passive cap bridging has poor performance. \$\endgroup\$ Commented Jul 8, 2019 at 16:21

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