Most household power circuits in Australia have circuit breakers that
allow no more than 16A of current on the circuit. It is common for
large transformers to exhibit enough inrush current to trip a 240V 16A
circuit breaker. Electrical appliances as simple as a 115V toaster
will likely require not only a transformer with at least 1500W power
output possible, but the transformer itself may exhibit enough inrush
current to trip the circuit breaker almost every time the transformer
is activated.
There are three solutions to this problem.
- Replace all electrical appliances that use greater than 500W
of power (i.e. sell the appliances in the USA prior to moving, then
purchase new appliances in Australia). Isolation transformers and
autotransformers rated up to 500W generally don't have an inrush
current problem that will consistently trip breakers.
- Have an appropriately licensed Australian electrician install a
115V 50Hz service in your new Australian house. Such a service
would place the transformer on the street side of the breaker box
and the transformer would be permanently energized. The house
would be wired for both a 240V and 115V service.
- Purchase and use an inrush current protection device.
Under no circumstances should a 16A breaker be
replaced with a higher current breaker to solve this problem. High
current breakers can allow hazardous electrical situations to
persist long enough to injure or kill.
An inrush current protector will attempt to regulate
transformer inrush current. An inrush current protector uses an electrical
relay to switch the initial transformer inrush current through a high power
resistor. Once transformer inrush current has subsided to a given low
level the electrical relay switches the active power line to a 0 Ohm
circuit directly to the transformer.
See this page for a link to Ameritron.
This company makes a 240V inrush current protector that is suitable for 2000W
applications. Ameritron publishes a schematic for the device on their
web site.
Some notes about the Ameritron ICP-240 (in addition to the user
manual that comes with the device):
- The ICP-240 comes with a NEMA 6-15P plug and 6-15R receptacle, which
no doubt makes it suitable for 240V 2 pole 3 wire 15 Ampere AC receptacles
in the USA. This plug and socket configuration is not common in Australia
and adapters appear to be non-existent. If you are using a Hammond unwired
170JE 2000W autotransformer (described here)
then the simplest workaround for this
is to chop off the NEMA 6-15P plug and replace it with an Australian
plug (available in many stores). Next replace the 240V input plug
on the transformer with the NEMA 6-15P plug removed
from the ICP-240. Warning: don't cut the NEMA 6-15P too close to the plug
as the cut point determines the distance between the transformer and
the ICP-240. If you do not know how to wire Australian or NEMA 6-15P
plugs then you should not attempt to use the ICP-240 for this
application.
- The transformer should be the only load on the ICP-240 when it is
activated. If other excessive load is on the transformer when it
is energized then the ICP-240 internal relay will be unable to switch
the power resistor out of the circuit. High current will flow through the
power resistor for an extended period of time. This will either cause
a fuse in series with the power resistor to blow, or will cause the power
resistor to burn and fail. The simplest solution for
avoiding this situation is to unplug the transformer output
prior to activating the inrush current protector. Once the transformer
has been energized it is safe to connect appliances to the transformer
output.
- The ICP-240 lists valid input as 240V 60Hz. The device seems to
operate correctly at 240V 50Hz single pole.
- Have Ameritron ship using a trackable shipping service such
as UPS.
- Canford in the UK also
manufacture an
inrush
current protection device. I have not used this device, but its
specifications are suitable for Australia and it uses the more common
IEC connectors for input and output.