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The complete guide to running your 3 phase 415V machines on a single phase 240V supply by Drives Direct(Inverters) LTD

This guide will assist anyone looking at purchasing any type of 3 phase converter equipment in deciding on the best option for their particular application, there are a number of types of phase converters available and deciding on the best option is often not an easy task as there is a lot of confusion over the different types out there and the options available,

If you find the information in this guide useful please let us know by clicking YES to the question "Was this guide helpful?" at the end of the guide,

Many people will at some time come across a 3 phase machine they would like to power up in the home, 3 phase machines often come up at fantastic prices in auctions from companies closing down and they often go at a very low price because they are three phase,

One thing that often happens is that people look round at auctions and see a machine they like and they will look at the motors rating plate and see 220V and then assume they can run the machine on a normal household supply and its not until the electrician turns up to install the machine that they realise the machine is in fact a 3 phase machine and will not run on a normal domestic 240 Volt single phase supply,

Often getting a three phase supply installed from the national grid can be an expensive and time consuming task and it can lead to other complications as well, when you get a quotation its likely to be prohibitively expensive and even if you were to go down that route the quote will normally only cover groundwork's from the nearest 3 phase cable to the boundary of your property, you are then responsible for the excavation and making good of the trench on your side of the property, it can take months before they start the work and then when you get your supply the chances are the commercial rate tariff they offer you will be far more expensive than a domestic tariff and often there will be a daily standing charge to be paid even if you use no 3 phase at all that day !, also if you are in a domestic situation you can end up with the council contacting you to find out why you have had an industrial supply fitted to say your home garage and seeing if they can now charge you for business rates then the council get involved and start asking for a planning application for change of use to a business !, not a great start and not ideal even if you are looking to set up a small business from home, if you are renting a small industrial unit that does not have 3 phase then often 3 phase will be on site already and so the cost of getting it connected will be far lower than in the domestic situation BUT if you think about it having 3 phase installed even at a reduced cost is not always the best solution as in effect you are paying for something that you can not take with you, the landlord will have the benefit of the three phase if you decide to leave, its is often much better to spend the money you were going to spend on having the 3 phase installed on a phase converter then if you leave you can simply take your phase converter with you, if you end up moving to a place with no three phase you can use the phase converter again and if you close down or move to a premises with 3 phase installed already then you have a valuable asset you can sell on,

For small 3 phase machines and in cases where you only have one 3 phase machine and especially if that machine is fitted with the DUAL VOLTAGE motor then fitting an inverter will be the cheapest way to get your machine up and running, basic inverters are only small units and they need to be wired into your machine BUT once fitted you then have in effect a SINGLE PHASE machine and if you ever resell it you will be able to get a much better price for it as a single phase machine than you could hope for in its 3 phase format,

You will find that 90% of the motors out there that are under 5 HP and were made in the last 30 years will be fitted with DUAL VOLTAGE motors, basically a dual voltage motor is one where you can select the voltage it runs from simply by exchanging the links in the motors terminal box, this connection is called STAR and DELTA mode, in STAR mode the motors running voltage will be 415V where as in DELTA mode it will be 220V, for the manufacturer of the machine having a dual voltage motor is an advantage if they ever export the machine as in some countries their 3 phase voltage is 220V so if they had a drill for example and wanted to sell it in the USA then simply by changing the links in the motor to DELTA and replacing the coil in the starter switch box from a 415V coil to a 220V coil the machine would run just as well on American 220V three phase as it would here in the UK on 415V three phase, this is also an advantage for you if you want to run the machine here in the UK, this is because if you were to swap the links over to DELTA mode you would then be able to run your motor from single phase simply by using a BASIC 240V INVERTER, for the 240V inverter this is an easy task as all the inverter has to do is take your 220V single phase input and change it to 3 phase, the voltage is not changed and as its a comparatively low voltage this range of inverters are not at all expensive and they are physically very small, in fact for motors up to 5HP you can hold them in than palm of your hand at arms length !,



The linking method shown above is the most popular method used BUT there are other methods in use so if your motors rating plate says it's a DUAL VOLTAGE motor BUT the configuration in the motors connection box does not look the pictures above then please contact us and we will talk you through the required connections.

If you have a machine that is NOT fitted with a DUAL VOLTAGE motor then you can still use inverter technology but as the motor requires 415V 3 phase then you will require a DUAL STAGE inverter, this is very similar to the 240V inverter product in that it changes your 220V single phase in to three phase BUT it also boost's the voltage up from 220V to 415V, On the downside of this because the DUAL STAGE inverters are twice as complex as the SINGLE STAGE 220V output units and working at higher voltages they tend to be far more expensive than the BASIC 240V versions and if its practical to change the motor to a modern DUAL VOLTAGE type then often you can get a package of motor and inverter for less than the cost of the DUAL STAGE 415V output inverter, where these DUAL STAGE inverters often prove most useful are in cases where its not practical for whatever reason to change the motor for example a power feed motor where the case of the motor is part of the machines casting, 

Both of these inverter options will offer you other benefits as well, they have a built in SOFT START, this function will allow you to set the time it takes for the motor to reach full speed after switch on, this is good for your machine as it reduces the shock loading on the machines power train at start-up as well as reducing the surge on your incoming supply, inverters also offer you FULL SPEED CONTROL of your motor, this is very useful on some machine applications as where you would normally need to change belts to alter the chuck speed now you can simply turn a knob and the inverter will change the speed for you, these inverters also feature a brake function to slow down the motor after you stop it, this is great for say woodwork machines where having this function enabled will allow the machine to comply with HSE regulations by stopping the blade within the 10 seconds as required,

If you are looking to power a whole workshop or if you machines contain electronics like welders or CNC machines then you need to look at either the modern DIGITAL PHASE CONVERTER option or the old fashioned ROTARY PHASE CONVERTER for those on a tight budget with a less demanding application,

A ROTARY CONVERTER is not the perfect phase converter but its one step up from the STATIC, the term ROTARY comes from the fact that these have an internal motor running and this is used to assist the unit produce the third "PHANTOM" phase, this phase if often not at the ideal voltage or even the correct phase shift that TRUE 3 phase requires BUT its close enough for a large range of less demanding applications and its cheaper to purchase than the DIGITAL PHASE CONVERTER systems, on the down side the unit is noisy because of the internal motor running and that motor is using power all the time even if you are not running any machines from the converter, the amount of power wasted gets worse the bigger the converter due to the larger motor being powered, also due to the miss matched phase and voltage output from the rotary phase converter you will loose a small amount power and the motors wont be running as smooth as if they were running from a true 3 phase supply like the DIGITAL PHASE CONVERTER will give you,

For small hobby applications on a tight budget this may well be acceptable as the converter will often be at the lower end of the power range for converters so the constant power waste will be smaller AND its often not a problem for a hobby user to turn the converter off when its not in use and then switch it on again when they need to use one of the machines, in this case the machine being powered will often be making more noise than the converter so the noise aspect of the rotary converter will not be a problem,

Rotary converters are NOT recommended for applications requiring 3 phase power 24 hours a day

For any demanding applications where the quality of the power is important such as CNC machines, precision equipment or equipment with electronics or for industrial use where the unit may be switched on 8 hours a day or more running a workshop for example or on an application that requires a 24 hour 3 phase supply for example with ground source heating systems, pool filtration, HVAC systems, water pumping, passenger lifts etc then you should look at our DIGITAL PHASE CONVERTER systems, these DIGITAL converters have perfect phase output voltage and phase angle and they run without any pilot motor so they are very economical on power and they produce very little noise and are rated for 24/7 operation,

Types of phase converter :-


A DIGITAL PHASE CONVERTER is basically the MODERN VERSION OF THE ROTARY CONVERTER and is the best solution for today's demanding power conversion applications,
These units will convert a single phase 240 Volt supply into a 415 Volts 3 phase regulated output,  these digital converters are truly versatile and they are available in variants that can work from almost any supply, 210-250V is the normal input voltage range and they will give a constant output voltage over this range, you can opt for 440v or 480v BI PHASE as often found on farms and the units will work from a 50Hz or 60Hz supply and are totally happy running from a generator,
The output is also adjustable, in standard form it will be 415V 50Hz 3 phase but you can have anywhere between 200V and 480V 3 phase at 50Hz or 60Hz and even 400Hz is available as an option to enable the powering of for example military equipment or high frequency grinding tools as often found in a founders fettling shop and woodworking routers and spindle moulders are another example where often a DIGITAL PHASE CONVERTER can replace a noisy, inefficient and unreliable motorized frequency changer, in its basic form as long as your machine requires a 3 phase + earth supply and consists of just motors and control gear you can simply plug in your machine to the converters output and run it hence the term PLUG & PLAY often applied to a DIGITAL PHASE CONVERTER,
For powering machines with electronics as part of the control system you will also require a SINE WAVE FILTER, once you have this option fitted its possible power machines such as welders, plasma cutters and even running a CNC machine is possible, you can take the DIGITAL PHASE CONVERTERS output and run a main around your workshop and plug in and run your machines in any combination as long as you don't exceed the total power rating of the converter,
You have to take into account the STARTING SURGE required by your machines when sizing up your converter, at START UP a 3 phase motor wired for DIRECT ON LINE(DOL) starting will draw between 3 & 8 times the normal running power, how far up this scale the surge will be all depends on the inertia of the load that the motor is driving so for example a milling machine like a Bridgeport with a 2HP spindle motor will be at the lower end on the scale and require a starting surge of approx 6 HP where as a 5 HP planer machines with an 18" cutter block may well require 5 times the normal load so will need approx 25 HP to get it running, the DIGITAL PHASE CONVERTER has a built in overload capability so whatever size converter you go for it can handle a 150% overload for 30 seconds,
The converter has an inbuilt OUTPUT VOLTAGE REGULATOR, this system monitors the output and will adjust the internal power stages to compensate for the load applied to the system as well as compensating for power input fluctuations, in fact this unit will take from 210 Volts up to 250 Volts and still give you a regulated 415 Volts per phase output so its happy to run on generators or sites where the mains supply is not very well regulated, 
Should you have a machine that as well as three phase also requires a NEUTRAL line then that's also possible with the addition of a NEUTRAL GENERATOR but as a N line is simply a way that a machine can get 240 Volts back from the 415 Volts 3 phase to power some low voltage item within the machine we will often be able to talk you through feeding an external 240 Volts supply to whatever requires it thus saving on the cost of the NEUTRAL OUTPUT option,
DIGITAL PHASE CONVERTER units are also fitted with a BOOST option, this is an ENERGY STORE rather like a short term battery, it charges up when your machines are either OFF or running at normal power, this takes less than two seconds to do BUT when ever you start your machine and it requires the STARTING SURGE rather than drawing the required power to get the motor up and running from your mains supply it is taken from the BOOST PACK, this helps you to get large machines up and running BUT is also buffers your incoming supply from these surges so you don't get your lights flickering each time you start a machine  this way you wont annoy the wife in the house while you are out in the workshop welding for example, the level of boost can be extended at the time of purchase for applications that require more than the STANDARD BOOST capacity,
All in all the DIGITAL PHASE CONVERTER is the perfect system, its reliable, quiet, uses very little power and its highly efficient and can be adapted to suit a wide range of applications,


These are an electronic device that can take a 240V single phase input and give you a three phase 240V output, because the output voltage is 240V rather than the normal 415V people associate with three phase your motor needs to be a DUAL VOLTAGE TYPE for them to run from this type of inverter, you can check to see if your motor is compatible by looking at the motors rating plate, if it has 220V as well as 415V  on there then it will be able to run from this type of converter, you have to have a direct connection between the output of the inverter and the motor you are powering, this is very easy to set up and if offers a number of advantages as once the motor is connected the inverter then has full control of the motor and it can then give you the extra functions like SOFT START, electronic brake and SPEED CONTROL, you are also able to add a remote control pendent to this converter to allow remote switching/speed control while the converter can be tucked away out of harms reach, these come in power ranges from ¼ HP up to 5HP


These offer all the functions of the basic unit BUT they are what's known as an ADVANCED VECTOR INVERTER, this has the advantage of allowing control of your motors speed without loosing power, on the basic inverter the power of the motor will reduce as you reduce the speed but with the vector version this does not happen and that's fantastic for application like lathes etc where you can do away with the belt step change and use one of these units to give speed control, the advanced unit is also able to link up to the advanced pushbutton remote station as well as the basic remote control box, these ADVANCED INVERTERS can do a whole load more than described here like interfacing to a computer for remote control on applications like CNC machines and these are available in power levels from ½ HP up to 5HP  and they are also available with a 240V single phase input and a 415V 3 phase output.

240V to 415V INVERTERS

This range of converters offer the same functions as the basic and advanced units BUT these give out a 415 Volts 3 phase power supply from your 240V single phase input, because of this you do not need to have a dual voltage motor for these to be able to power it and they can run 415V motors at full power,

This is fantastic for applications like on the Bridgeport mill where the motor requires 415V and its not practical to replace the motor as its case is part of the head casting, DUAL SPEED motors are another example of applications where these inverters are useful as you can still have the two electrically selected speeds on your machine,

This range of DUAL STAGE inverters range in power from 1HP up to 5HP in the BASIC model and 1HP up to 30HP in the advanced version and there is a version with a 440V BI PHASE input, this is a supply oftern found on farms and inverter units that can power motors up to 50HP are avaliable on a BI PHASE supply.


These are the most basic type of phase converter unit and they have been around for years, they often take the form of a large and heavy blue box with a few switches and often a meter, this type of converter is in fact a very simple device,
a typical unit will contain a 240V to 415V transformer, a relay switch connected to a bank of capacitors and some form of voltage sensor to control the relay switch, basically the 415V output from the transformer will become 2 of the output phases and the capacitors are placed between one of these phases and the third phase line to create the PHANTOM PHASE, how many capacitors are connected is controlled by the relay and also the power level selector switch, the relay will switch more capacitors in circuit to help get the motor started, it will disconnect them once the motor is up and running leaving just RUN capacitors in circuit, the power switch will then select how many RUN capacitors are left in circuit once this start boost has ended, the idea is to TUNE the converter to match the motor you are powering by selecting the number of RUN capacitors in the PHANTOM PHASE circuit, 

This is all well and good BUT there are a number of problems, its very hard to get the match of capacitors correct and a mismatched set-up will cause the motor to run rough, run hot and run with reduced power, even if you were to get the match the best theoretically possible the PHASE SHIFT of the PHANTOM PHASE can never be the 120 degrees it need to be as you would get on a true three phase system so you will always find the motor will be running down on power and often the running will be rough when compared to running on a true three phase supply, in precision machines like for example metalwork lathes this rough running can often be noticed in the quality of the work produced and people have often commented on this problem to me,

The next problem that we have experienced is people burning out motors when using a STATIC type phase converter, you will notice that there will be a MINIMUM size motor listed on the specification of a typical STATIC converter, the bigger the MAXIMUM size of motor the converter can run the bigger the MINIMUM motor will be, as an example a 5½ HP STATIC will have a minimum load of ¾ HP, this is because of the size of the capacitors in the RUN circuit when the power switch is at the minimum setting, there would be too much capacitance in the system to run any motor less than ¾ HP, as often the suds pumps on a typical lathe or milling machine are often around the ¼ HP range if you try to run that motor on its own it would be far from happy as the PHANTOM phase would be being overrun and with time the motor would be burnt out, the solution here is to only run the SUDS PUMP when the MAIN MOTOR is running, you do need to be very careful about this, take for example the case of a lathe being run with the main motor on and the suds pump, because the main motor is larger than the suds pump you may have the converter power setting up to the level required for say a 3HP motor, if you were then to turn off your main motor  BUT leave on your ¼ HP SUDS PUMP it would be subject to the PHANTOM PHASE power required for the 3 HP main motor as its life would be over in a very short time !,

Often because of the nature of the PHANTOM PHASE a STATIC CONVERTER can have a problem running some motor types, DUAL SPEED motors are one example as often one of the speeds on your motor will not run at all !, some aluminium motors will not run correctly, its often a trial and see situation, this interaction between the motor and the PHANTOM PHASE can cause other problems with machines control gear and you need to be sure that any control circuits are wired to the MAIN POWER phases that come direct from the transformer and NEVER connect them to the PHANTOM PHASE or you will run into problems for sure and this has in some cases I know of resulted in the demise of machines DRO for example, for this reason a STATIC PHASE CONVERTER can not be used to run machines that are none motorized or machines with electronics in them for example WELDING EQUIPMENT etc,   

So as far as STATIC PHASE Converter's go we can conclude that for running basic motorized machines in a hobby "ONE MACHINE AT A TIME" environment and with careful use in applications where power level and smoothness of power delivery are not important the STATIC CONVERTER will enable you to run your machine,

As far as purchase price goes the STATIC Converter's price is low in comparison to other converter types and there are even guides on eBay that tell you how to make your own at a fraction of the cost of purchasing a ready made unit(search for phase converter guide) BUT if you only have one machine to power and its fitted with DUAL VOLTAGE MOTORS then an INVERTER will be the cheapest option and offer many advantages.



A ROTARY converter is basically one step ahead from the STATIC CONVERTER, in most cases it the same basic design as a static BUT with the addition of a large PILOT MOTOR and no power boost switch, the unit has been set up to match the PILOT motor fitted and because there is a motor running all the time you can run more items from this type of converter, other methods are out there, some dispense with the input transformer and use a special motor that acts as a transformer as well as being the ROTARY element of the converter, on other designs there are automatic power switches to help balance the PHANTOM PHASE as it comes under load, even with these extra gadgets fitted a rotary converter is still not the perfect phase converter by any means, the third "PHANTOM" phase is often not at the ideal voltage or even the correct phase shift that TRUE 3 phase requires BUT its close enough for a large range of less demanding applications and its cheaper to purchase than the DIGITAL PHASE CONVERTER systems, on the down side the unit is noisy because of the internal motor running and that motor is using power all the time even if you are not running any machines from the converter, on larger size converter this power loss can equate to the equivalent power of 2-3 electric kettles !, also due to the miss matched phase and voltage output you will loose a small amount power and the motors wont be running as smooth as if they were running from a true 3 phase supply like the DIGITAL PHASE CONVERTER will give you, reliability can be a problem as well with a rotary due to the mechanical element and the high stresses the capacitors are subjected to, if you were to contact the manufacturers of these unit and ask them if you can run one 24H/day you will most likely be told to get two units and have a time switch to run one for 12 hours and then switch over to the second, YES you do get a three year warranty BUT you have to ask yourself if the manufacturer is not happy for the converter to run 24 hours a day then there is a good chance they suspect that it may well fail within the three year guarantee period if subjected to this type of use, whilst on the subject of warranty's please do check the small print as you will see that with some manufacturers the warranty will only be valid if the run capacitors are replaced every year !, make what you will of these facts but if 24/7 operation is required again look at the DIGITAL PHASE CONVERTER,
For small hobby applications on a tight budget the rotary converter may well be acceptable as the converter will often be at the lower end of the power range for converters so the constant power waste will be smaller AND its often not a problem for a hobby user to turn the converter off when its not in use and then switch it on again when they need to use one of the machines but constant switching on and off does put great strain on the starting circuits and so doing this may well reduce the units life expectancy, if you are going to do this switching on and off then the machine being powered from the converter will often be making more noise than the rotary's motor so this aspect of the rotary converters design will not be a problem,
Rotary converters are NOT recommended for applications requiring 24 hours a day running.

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