What would you like to do?
Can you replace a 480-240V 3-phase motor with a single phase motor as a temporary replacement or will it burn it out?
Yes, you can, and it won't burn out IF>>> the horsepower rating is the SAME. Pay attention to wiring and motor rotation.
Also check the voltage: the motor voltage must be the same as the voltage between two hots of your 3 phase system. You will only use two hots as this is a single phase motor.
Was this answer useful?
Thanks for the feedback!
The load of the motor itself is constant and it will try to achieve it's running RPM. If the supply voltage decreases the amperage needed increases to where the motor wi…ndings cannot sustain the current flow without producing excessive heat. Hence, SMOKE!
Yes, each of the 3 phases can be it's own single-phase supply. So only one of the phases would be used for a single phase motor. As long as the voltage is correct and the wiri…ng can handle the current requirements, then it should work fine. Answer To obtain a single-phase supply, you need to be able to connect your motor either between any two line conductors (three-wire systems), or between a line conductor and a neutral conductor (four-wire systems). Of course, its VERY important the voltages obtained in this way match that of the motor.
Use only one of the legs (L1-L3), and the neutral. Some three phase circuits don't have a neutral. If that is the case, then you cannot run single phase. Comment You don'…t need a neutral, providing the voltage is appropriate, you can get a single-phase supply by connecting the load between any two lines.
Yes. Simply connect the motor across any two of the lines. Make sure, however that the line-to-line voltage is the same as the rated voltage of the motor. The reverse does not… apply. Do not connect a 3-phase motor to a single phase supply. Yes, and be aware of a possible "high" leg in your 3ph supply. Some pole transformer conections for 3ph have a high leg delta connection(wild-leg). For instance, 240v 3ph line to ground voltages could read 120v, 208v,120v for the 3 consectutive lines. Of course you want the outer two lines from your panel as the center line should be your "High" leg. For 3ph to 1ph, use a phase converter or build one yourself.
Three-phase motors will run on single-phase power. What they WON'T do is start. There is no easy way to re-wire such a large motor to run on a single phase. Properly sized c…apacitors and a special relay is sometimes used on sewage lift stations (poopie stations is what we call them) to run the 3-phase pumps on single phase. I've seen 10 hp motors used. Sometimes a lift station is needed where 3-phase power is not available The motor will not develop it's full horsepower, only about 2 thirds. A push-button can be used in place of the relay, but you will have to push the button until the motor starts then let go. If the motor stops you will need to push the button again. Usually expect several hundred micro-farads to be needed. I have used old A/C motor-run capacitors in parallel to experimentally determine the actual size (capacitance) needed. Be sure to use correct working voltage capacitors. DANGER!!! Electricity can EASILY kill you and capacitors can blow up in your face!!! I've seen crazy people attempt to rope-start three-phase motors (it works), connect phase converters, all sorts of weird stuff. In reality, single-phase 5hp motors are available, so the a good recommendation is to trade-in the 3-phase motor for a 1-phase motor of the size you need. To run a three phase equipment from a single phase source, you will need something called a "phase converter". Before you go out and buy one, find out if a single phase motor is available to match your requirements. It will probably be an easier solution for you if you can do that. Depending on your application, another option with such a large motor is to get a "Variable Frequency Drive". These are somewhat expensive but will take in a single-phase input and output 3-phase. As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed. Before you do any work yourself, on electrical circuits, equipment or appliances, always use a test meter to ensure the circuit is, in fact, de-energized. IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB SAFELY AND COMPETENTLY REFER THIS WORK TO QUALIFIED PROFESSIONALS.
A 3 phase 5 hp motor is a fair size motor and I must say up front that if you don't know how to, you might not should be doing so without a licensed Journeyman electrici…an. If you make one wiring mistake, the motor may burn up and they aren't cheap! With that said, a 3 phase motor has different wiring hook ups for low voltage, (208-240 volt) and high voltage ( 480 volt). A 3 phase motor has nine wire leads inside the "make up" cover. They will all have a number tag on them from 1 through 9. Your incoming three phase power of course has three "hot" legs which from left to right in the panel are A,B and C phase. These wires should be color coded for 208-240 as: Black (A phase) Red (B phase) and Blue (C phase). For 480 volt these colors will be Brown(A) Orange(B) and Yellow (C). The A,B & C phases are the line voltage conductors and are to be considered as L1,L2 and L3 when connecting to the motor. The correct connection for a low voltage (208-240V) 3 phase motor which is "Y" or "star" connected internally is: Connect The L1 (A phase) to wires # 1&7 on the motor (wire nut or split bolt all three)Connect the L2 (B phase) to wires # 2&8 Connect the L3 (C phase) to wires #3&9 Then connect motor wires # 4, 5 & 6 together Make certain you ground the motor properly!! The correct connection for a high voltage (480 V) 3 phase motor which is "Y" or star connected internally is: L1 to motor lead#1, L2 to 2, L3 to 3, then: connect motor leads 4&7 together, 5&8, and 6&9. Again, these connections are for Y connected motors. Almost all are these days as powers companies have gone to a standard delta to Y step down in voltage transforming. Again, if you're not clear on this or haven't wired large motors before, I highly recommend you hire a licensed Journeyman electician to do it. Remember, the physical wiring connections are critical and must be done well. They should be made with a brass split bolt, rubberized electrical tape and then high temp electrical tape. Motors vibrate and bad connections will come loose, causing an open or short circuit, or worst case for the motor to single phase and burn up.
The winding design of the motor will not economically allow this to work. You would have to drive a 3 phase generator to supply it.
A three-phase motor will not start if one or two phases aren't connected. If while running one or two phases "drop out", it will continue to run for awhile, but will eventuall…y burn out, unless connected to a motor saver.
The sine waves of a 3 phase power supply are 120 degrees apart, in a single phase supply they are 180 degrees apart. Three phase motors also consume almost half the amperage o…f the same HP single phase. Simply put, there are three "power" wires for the 3ph compared to the two for 1ph. 3ph induction motors do not use capacitors or separate windings to get them turning as 1ph motors do, therefore less separate/moving parts to contend with.
A single phase induction motor has two sets of coils and a centrifugal start switch. The start winding is in series with the start switch. The start winding provides a rotatin…g magnetic field in one direction enabling the motor to start. The motor can be reversed by reversing the connections of either the start winding or the run winding but not both.
To run any three phase equipment from a single phase source you will need something called a "phase converter" that can handle the full power of the motor. Phase convertors …are very expensive so, before you go out and buy one, find out if a single phase motor is available to match your requirements. It will probably be an easier and cheaper solution for you if you can do that. If you already have a three phase motor that is in good condition, you may be able to find a local dealer who would part-exchange it - or even swap it - it for a good quality used single phase motor with a warranty. It is simply not worth destroying a perfectly good three phase motor! Converting or rewiring a three phase motor to run on single phase is not a simple job to do, nor is it worth doing, because the work required would cost a lot to do. It is simply not a practical proposition. That fact is true even for a professional electrical engineer who has all the right equipment to be able to do it.
use starting capacitor
You cannot run a three-phase motor on a single-phase supply. You can if you have 1phase to 3 phase inverter The physical internal windings between single phase and three ph…ase motors makes this an impossibility That being said money can make anything happen. Depending on the amount of money you want to spend to make this happen there is a device on the market called a VFD ( Variable Frequency Drive). On the three phase input terminals you apply your single phase voltage. On the output terminals you connect your three phase motor. When run in this configuration there is an internal switch that has to be changed to let the VFD know that it should be looking for only two lines on the input to be hot. Other wise the VFD thinks that there is a line loss on the three phase input terminals and the unit will not start.
If the compressor currently has a 3-phase motor connected to a 3-phase service, then, unless there is also a single phase branch circuit outlet available at the same location,… which already has the right sizes of breakers and wiring to suit the motor's power requirement, it is not a simple matter to change the motor to a single phase type having the correct power output and motor controls. If there is no existing single-phase outlet that is suitable then: either a new single phase service would have to be installed to suit the single phase motor which is being asked about to be used as a possible replacement or it would be necessary to change the circuit breakers, wiring and outlet connections of the present 3-phase service to have the correct parts to make a single phase service that would suit the single phase motor which is being asked about to be used as a possible replacement. As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed. Before you do any work yourself, on electrical circuits, equipment or appliances, always use a test meter to ensure the circuit is, in fact, de-energized. IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB SAFELY AND COMPETENTLY REFER THIS WORK TO QUALIFIED PROFESSIONALS.
Two options: Option 1 is to copy the motor data tag info for FRAME (FR) and HORSEPOWER (HP) and get a motor that matches those two factors in single phase. Option 2 is to get …a variable speed drive (VFD) rated for single phase input and three phase output at the amp rating of the motor you have. This is my personal choice as it gives you the ability to vary the speed of the motor as well.
Use VFD to make 3 phase from single phase source.