What about line drop, voltage variations, electrical noise and wire sizes?

The current in a wire causes heating in proportion to the square of the current times the voltage (known as I2R heating). Also the voltage available at the start of the wire is not quite the same as the voltage available at the end of the wire. In rural location where a single-phase line supplies a couple of farms the voltage can drop as low as 200 V at times at the end of the line (such a large line drop is excessive but instances of this do exist where the utility companies are being parsimonious to the extreme). Also the utility company is permitted to vary the line voltage over a given range - the range was recently widened as part of the European harmonisation process and will reduce over the course of the decade as the nominal supply voltage is reduced from 240 V to 230 V. So what you get at your house's fuse board might not be the steady 240 V you expected - at Boost's premises we tend to get about 242-243 V but with a slightly clipped waveform. The easiest thing is simply to measure what you have a few times a day over the course of a week and make a note of the likely supply voltage. Good quality phase converters are provided with a range of tappings on their transformers and you can then shift the tapping in use as appropriate when you install your converter. The reason that the phase converter manufacturer cannot do this in advance is that there is a legal obligation to despatch newly constructed electrical equipment with the 230 V tapping selected.

The same line drop phenomenon can occur on a smaller scale at your premises. Typically the consumer unit is towards the front of the premises whereas most workshops tend to be tucked away at the back of the garage or down the garden. So there can easily be a hundred feet or so of cable that might not be of sufficient size (i.e. cross sectional area) to transport the required current. However you must not shift the transformer tapping to compensate for any steady state line drop within your premises, instead you should install a larger cable !! Remember that an overloaded cable is a long electrical heater and at some point it is doing the heating in your house and can act as an ignition source.

In any case it is in your machinery's best interests to install an adequately sized cable (a cable is the term for something with more than one wire in it). This is because whereas the line drops discussed above are steady state affairs, a similar thing occurs over a much shorter timescale when starting a motor. If there is a constraint in the electrical system, when current increases voltage will fall - and your motor will not accelerate to full speed as rapidly as it ought to. We have observed the voltage fall to 180 V or so when conducting tests at a client's premises where the cable to the workshop was simply inadequate.

Sizing wires to ensure that you don't have too much voltage drop is most important in the longer cable runs. A good on-line calculator for this has been written by Jeff Lucius and is at www.stealth316.com/2-wire-resistance.asp together with explanations.
To a certain extent a rotary phase converter is better than a static in locations where the electrical supply is weak. This is because the motor or rotary transformer acts as an energy storage device (both because of the mechanical flywheel effect and the equivalent magnetic field storage), which is available for release during start-up of the driven load. Automatic line drop compensation is possible but to date has not been economic to provide.

Low frequency voltage / current variations can be transmitted via the phase converter. These occur because the machine tool is a pulsating load and, if the electrical supply is constrained, then either the voltage or current will vary in sympathy. The worst case of this that I observed was a 15-hp hydraulic blacksmiths hammer with a reciprocating motion at about two cycles per second. Even though the highly geared motor turned at about 1200 rpm the torque variations were sufficient to cause a noticeable flicker in the lights at a rather annoying 2 Hz or so which affected the nearby houses. This was at the end of a very long electrical supply line in a rural location. It is possible to insert filters to overcome these effects but they tend to be expensive and it might be cheaper to buy your neighbours a bottle of wine - and you can be pretty sure that everyone's lights flicker when a washing machine starts. Converting your machine tool to single phase motors would actually exacerbate such a situation as it is the machine tool that is the source of the flicker rather than the phase converter, and a single phase motor has a less constant torque delivery characteristic than a three phase motor.

The only high frequency voltage components a static or rotary phase converter is associated with originate from switching the capacitor banks (for boosting or to adjust power levels). This is an infrequent exercise unless a fully automatic control system is installed and the load is varying a lot (or the automatic circuit is failing), or unless a boost circuit is chattering. If this is the case then the phase converter will probably cause radio frequency interference, as the electromechanical contactors that are used are terrible in this respect, but this switching is not a normal operation. In fact in normal operation a phase converter cannot cause radio frequency interference (again, unless something is failing) and in this respect they are superior to inverter drives.