STATIC VS. ROTARY PHASE CONVERTERS
Static and rotary phase converters both turn standard single-phase electricity into three-phase power for heavy-duty equipment. The difference is that a static phase converter will start a three-phase load, but run it under lower power, while a rotary phase converter creates continuous, well-balanced three-phase power.
Why would you need to convert single-phase to three-phase power? Single-phase power is the common residential and light-commercial variety supplied by utilities, used in places with smaller electricity loads requiring less power. Three-phase utility service is used in large industries, factories, and in manufacturing units where a large amount of power is required.
But here’s the problem. All kinds of equipment require three-phase power: machines for woodworking, metalworking, CNC machining, foodservice, and farming, just to name a few. A lot of this equipment exists in areas that don’t already have three-phase utility service. And getting it installed is enormously expensive.
So, what do you do? You get a phase converter, that’s what. There are two main types of these helpful devices: static phase converters, and rotary phase converters.
To determine which type you need for your application, you first need to understand the difference between the two. This article will help you understand that, as well as your main considerations so that you can make a smart decision.
STATIC PHASE CONVERTER
So, what is a static phase converter? The straightforward static phase converter will start a three-phase load but run it only under single-phase power, limiting the load to about 2/3 of its rated capacity.
Capacitors help start the three-phase motor, but then are disconnected once the motor is up to speed. At that point, the system is effectively only running lower single-phase power.
A static phase converter, although it is a simple and relatively low-cost way to start a three-phase load with single-phase power, is not usually suitable for heavy-duty three-phase equipment.
Common applications tend to be limited to lighter-duty types of:
- Drills
- Grinders
- Mills
- Lathes
- Saws
- Conveyors
- Ventilation systems
- Various food processing equipment
Many other types of equipment—vacuum pumps and air compressors being two prime examples—cannot be run at all with a static phase converter. If you decide to go with a static phase converter, make sure that it’s compatible with the power needs of your equipment. Feel free to contact American Rotary for help.
POWER DISTRIBUTION
When a static phase converter motor disconnects after starting up your equipment, you’re left with only two “legs” of power distribution. This is the reason the load must be limited to 2/3rds of its rated capacity.
POTENTIAL OF CONTROL
Potential of control refers to what you can power with a phase converter. In the case of a static phase converter, due to the inherent limitations we’ve already cited, only one piece of equipment can be managed at a time.
RELIABILITY
As noted before, with a static phase converter you’re running equipment at limited power. Run up against these limits, and you risk damage due to overheating.
In cases where you only need the higher power for startup of the machine, then you may be able to rely on a static converter for your needs. In other cases, you’ll ensure greater reliability with a rotary phase converter, which we’ll discuss next.
ROTARY PHASE CONVERTER
Unlike a static phase converter, a rotary phase converter is a more sophisticated unit that creates true three-phase power, often more precise than utility-supplied three-phase power.
POWER DISTRIBUTION
A rotary phase converter adds a small idler/generator motor (more on this in a moment) and control panel to the design, which gives you continuous three-phase power. This makes it a cost-effective option to provide three-phase utility to your shop.
POTENTIAL OF CONTROL
One of the biggest differences with a rotary phase converter is that, depending on the size of the system, you can run several pieces of three-phase equipment at a time. Rotary type converters are much better suited to large equipment and shops with multiple machines such as welding equipment, ovens and various woodworking machinery.
RELIABILITY
By supplying continuous three-phase power, a rotary phase converter is a reliable source of balanced power for your equipment. You can safely and reliably run several pieces of equipment at once.
WHAT IS THE IDLER MOTOR?
The idler/generator motor is the key to a successful rotary phase converter. In combination with a control panel, the idler supplies the continuous three-phase power.
You might have heard that an idler tends to draw a huge inrush current upon start-up, which can cause problems such as demand charges and large increases on power bills. But with all American Rotary phase converters, we use a custom-designed induction generator as our idler that solves this problem decisively.
Our VIT Induction Generator is a true soft start idler that uses 1/3 of the inrush current of a comparable three-phase motor—allowing you to run the phase converter 24/7 at little to no load without any negative effects. These idlers run very smoothly, quietly and efficiently.
