How to Choose

This guide will assist anyone looking at purchasing any type of 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,

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 realize the machine is in fact a 3
phase machine and will not run on a normal domestic 240 Volt single phase supply,

Example of a Typical Motor Rating Plate

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 !,

Example of a STAR Mode(415V) Connection

Example of a DELTA(220V) Mode Connection

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,

Some manufacturers will offer you a 3 year warranty BUT only if you replace the capacitors every year !,

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 :-

DIGITAL PHASE CONVERTERS

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 molders 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, we can offer up to 5 years warranty options on our Digital Systems

BASIC 240V INVERTERS

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

ADVANCED 240V INVERTERS

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 so because of this you do not
need to have a dual voltage motor for these to be able to power it, 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, these range
from 1HP up to 20HP and there is a version with a 440V BI PHASE input as often
found on farms that will power motors up to 50HP.

STATIC PHASE CONVERTERS

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 aluminum 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.

Drives Direct DO NOT sell STATIC PHASE CONVERTERS

ROTARY PHASE CONVERTERS

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 also be a problem with a rotary due to the mechanical element and the high stresses
the capacitors are subjected to,

Its interesting to note that most of the common manufacturers of the rotary converter sell them with a 3 year warranty BUT if you ask one well known maker of these items if its OK to run one 24 hours a day they will tell you that you need to have 2 rotary converters and a time switch to change them over every 12 hours, basically that tells me they do not expect the converter to last the warranty period !,

Another maker of rotary converters will also offer a you 3 year warranty BUT if you read the small print of the sales terms and conditions you will find a section telling you that the warranty is only valid if you have the capacitors replaced every year !, not good, either send the heavy converter back to them and pay for new parts to be fitted as well as the return carriage or buy the parts yourself and get an electrician to install them, none of these options would appeal to me and both of these facts set alarm bells ringing for me and it should tell you something about the general reliability prospects of the rotary 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,

Still interested in a ROTARY CONVERTER ?,

If so see the ROTARY CONVERTERS section of our EBAY SHOP or take a look at our plans on EBAY where we show you how to make your own converter at home.

All Drives Direct products are CE marked and comply with EMC Regulations, the Low Voltage Directive and BS EN ISO 61000-3-2:2006