competent licensed electrician, following national and local codes
should always perform the installation of a phase converter.
Unless the converter comes complete and is straightforward to
install, what appeared to be a bargain can turn out otherwise.
Static converters are low in initial cost and are
easy to install. Since they can only power motors and in
particular, single-motor loads, installation is straightforward.
Usually a disconnect will be required on the line side of the
converter, and a motor starter on the load side if the load does not
have its own controls.
Since the rotary converter is in essence a motor,
code requires the installation of a motor starter to start and
protect the rotary converter. Most rotary phase converters are
sold without the motor starter required on the single-phase line
side. The three elements required in a motor starter are a
disconnect, a magnetic starter and motor overload relay.
purchase and installation of this equipment can be a significant
hidden cost if the purchaser is not aware of the requirement.
On the load side of the converter, a three-phase motor starter will
be required to operate a single-motor load that does not have its
own controls. When used as a power supply, a three-phase load
center with breakers to protect wire on the circuits to the various
loads is essential.
Installing a VFD as a phase converter is relatively
simple and does not usually require much additional equipment.
They are a solid state device, so no starter panel is required on
the line side. All that should be needed is some kind of
disconnect. Since the VFD is designed to be a motor
controller, its output should be wired directly to the leads of the
motor load. It will both start and protect the motor load.
A VFD should be used only to power motor loads, and only single
motor loads. It should not be used as a power supply.
Sometimes the most difficult part of a VFD is programming the
parameters of the device. Simple start and stop
sequences are usually already set by the
manufacturer. More involved motor control schemes will usually
involve some programming.
Digital phase converters can function as a motor
starter to control a single motor load or as a power supply for
multiple loads or equipment with its own controls. Since it is
a solid state device connection to the single-phase line is made by
inserting the wires into labeled terminal blocks. A disconnect
should be installed on the line side. When configured as a
motor starter, the motor leads can be inserted into the converter
output terminal blocks. When the converter is turned on, it
will then start the motor load. The converter comes with a
control circuit that accepts input from a light duty remote switch
which allows the converter and the load to be turned on and off
automatically. This is especially useful in pumping
applications. When configured as a power supply for multiple
loads or equipment with its own controls, a three-phase load center
with breakers for multiple circuits should be installed to protect
the wire feeding the various loads.