Guide / Voltage, phase and frequency
Will it run on South African power?
This is the question that decides whether a machine works on day one or sits in the yard waiting for an electrician. The answer is usually yes — but for a reason worth understanding, and with four things to check first.
Frequency is the thing that matters
Voltage differences are an inconvenience. Frequency differences are a real problem, and they are the reason machinery from one part of the world suits us and machinery from another does not.
| Supply | Single phase | Three phase | Frequency |
|---|---|---|---|
| South Africa | 230 V | 400 V | 50 Hz |
| China | 220 V | 380 V | 50 Hz |
| Europe | 230 V | 400 V | 50 Hz |
| United States | 120 V | 208 / 480 V | 60 Hz |
An induction motor's speed is set by the supply frequency. Run a 60 Hz motor on our 50 Hz supply and it turns roughly a sixth slower, cools itself less effectively and produces less than it was rated for. The 20 V difference between 380 and 400 is trivial by comparison — industrial equipment is normally specified to cover both.
Four things to confirm about your supply
Compatibility is rarely the thing that goes wrong. Capacity is.
Do you actually have three phase?
Many workshops and small production units do not, and getting it installed is a utility application with a cost and a lead time attached — sometimes a long one. Check the distribution board and your bill before you order a machine that needs it, not after.
How many amps, not just how many phases
Having three phase is not the same as having enough of it. A rack oven or a large compressor can want more than the whole premises is rated for. The number you need is the main breaker rating per phase, and it is worth knowing what else runs at the same time.
The moment of switch-on decides the sizing
An electric motor draws several times its running current for the instant it starts. Supplies and generators sized on nameplate running figures trip the first time the largest motor kicks in under load. Where starting draw is a problem, a soft starter or a variable-speed drive is usually cheaper than upgrading the supply.
Someone registered has to certify the installation
Connecting a fixed machine is electrical installation work, and a certificate of compliance is issued by a registered person. Your insurer will ask for it after any incident. That work happens here, by a local electrician, and it is not part of a landed machine price — budget for it separately.
Three-phase motors can run backwards
If two of the three phases are swapped at connection, the motor turns the wrong way. On a fan or a pump that is merely useless; on some machines it causes damage. It is a two-minute check at commissioning and a trivial fix — swapping any two phases reverses it — but only if someone thinks to look.
Rural supply is not always clean supply
Voltage dips, phase loss and interruptions are harder on motors and electronics than most people expect, and machines with sensitive controls suffer first. If your supply is unreliable, that is an argument for simpler machines, and for protection on the ones you cannot afford to lose.
What buyers ask about power
Is imported machinery compatible with South African power?
Generally yes, and the reason is frequency. South Africa runs at 50 Hz, as does most of the manufacturing world outside the Americas, so motors turn at the speed they were designed for. Voltages are close enough — 380 V there against 400 V here on three phase — that industrial equipment is normally specified to cover both.
What about American or Canadian machinery?
That is where it gets expensive. North America runs at 60 Hz. Put a 60 Hz motor on our 50 Hz supply and it turns roughly 20% slower, with less cooling and reduced output. Some machines tolerate it, many do not, and conversion is rarely worth what it costs.
How do I know if I have three-phase?
Look at your distribution board and your utility bill. A three-phase supply has three live conductors and a main breaker rated in amps per phase. If you are not sure, an electrician can confirm it in minutes — and it is worth knowing the available amps, not just that it exists.
Why does starting current matter more than running current?
Because an electric motor draws several times its running current for the moment it starts. Size a supply or a generator on nameplate running figures and the biggest motor on site will trip it. The number that matters is the starting draw of your largest motor.