I found a Hunter DSP 9000 wheel balancer I would like to have for my home shop. The problem is it is 230 volt three phase. I only have single phase available to me.
Can anyone tell me if a static converter would work for this application or what is the cheapest esiest way to make something like this work?
I appreciate it!
The first question would be: how much power do you need to operate and
what is nameplate information on the motor? Then, what does this motor
doe? Are there any specific requirements on speed control or torque?
While not up on the actual technology available, such conversion is very
feasible using modern electronics. If I were starting from scratch, I
think I would rectify the line voltage and use pulse width modulation to
convert the dc to 3-phase. The electronics could be fairly complicated,
but I would not be surprised if there is a relatively low cost chip to
do all the complex job that could be connected to suitable transistors
Your best bet is to Google for vendors supplying frequency conversion
You can use a single phase to 3 phase converter but they may be more
than you want to spend. I would check with the manufacturer and see if
they had that unit with a single phase motor and could you buy the motor.
The cheapest way I know of is to get a surplus 3 phase motor larger than
the one in the balancer and some trivial components (like a motor starter
capacitor). The surplus motor is powered by the single phase 240V
feed and acts as a generator, generating three phase. You just connect the
A B C phases of the load to the A B C phases of the motor.
I don't remember any further details, but Google is your friend.
Static converters work for all but hard to start motors such as 3450 RPM
or higher speed motors, motors with direct coupled high inertia loads, or
motor designs with inherently low starting torque. Most 1725 RPM 3 phase
motors will start easily with an appropriately rated static converter,
but the wheel spin motor on a balancer might be an exception as the ones
I have seen start fairly slowly due to the wheel inertia. Since these
motors are fairly small a single phase input Variable Frequency Drive
might be a better alternative, but this requires rewiring the motor
contactor to the VFD RUN control terminals and direct wiring the VFD to
the motor. Either way you will need to be sure the single phase loads in
the machine are powered from your single phase line, with only the motor
connected to the derived phase of a static converter or the output of the
A quick check on eBay turned up a couple of single phase Hunter DSP
9000's for around $800, which might be more economical than getting a
converter for the 3 phase machine unless you are getting a really good
deal on it.
A rotary converter would also work, but with additional size and expense.
VFDs were mentioned, and yes in general that can be done. Normally, one
sizes the VFD at double the rating of the load if using it in this fashion
(single phase in, and three phase load on the VFD output). E.g., if the
load is rated 10A, 230V, 3 phase, then the VFD should be rated 20A, 230V.
The VFD will pull in a lot more than 10A on each of the two energized input
phases, in order to deliver 10A out on each of the three energized output
phases, and therefore needs to be rated higher than 10A to handle that
higher input current.
The VFD input current distortion will be very high. If this load is a fair
portion of your total load then this can become problematic.
VFD output voltages are kind of tough on motor insulation. The VFD output
is a PWM waveform with pulses that have a very fast rise time, which travel
down the wire and reflect, leaving the motor insulation subject to voltage
transients up to about 3x the nominal motor voltage. Over time this can
break down the winding insulation and cause the motor to fail. Where I am,
it is madatory that a motor that is connected to a VFD be rated and labeled
as 'inverter duty rated' (NEMA MG part 31) for this reason. I do not know
whether that is the case where you are. I have heard it said that motors
with Class F insulation and SF 1.15 are generally able to handle being
powered by VFDs fairly well. But, caveat emptor.
shop. The problem is it is 230 volt three phase. I only have single phase
available to me.
or what is the cheapest esiest way to make something like this work?
The balancer is 300 dollars. I would prefer a single phase unit, however I
live in a small area in Kentucky and not alot nearby. And of course shippin
g on such an item would be very expensive if purchased online.
I called the manufacturer and he said he would get me a price of the compon
ets needed to convert it but that it would probably be more thna I would wa
nt to spend. It would require a single phase motor, a new board, as well as
of course the plug.
I have read conflicting things on using a converter on a balancer. Some say
only the motor should be 3 phase and everything else within the unit shoul
d be single. Others have said everythign within is three phase. I have read
that you cant use a vfd or static converter. I read rotary converters have
very unplanced voltages on each of the legs so I wonder if this would affe
ct the accuracy of the balancer.
Kind of frustrating...
Without having either the balancer or it's schematic available the
questions you posed are unanswerable. You need to provide more
information to get anything other than suggestions of things you can look
into as already provided.
It is highly unlikely that the balancer computer/controler runs on 3
phase power. Most likely it will be powered from only 2 of the 3 input
leads, possibly through a single phase 230/120 control transformer. You
need to find or create (from inspection of the machine) a schematic for
power input to the machine controls including the rating of any
transformers, fuses or circuit breakers.
The motor nameplate will have the information required for specific motor
power recommendations. Essentially all info on the label is required,
including any design designation, insulation class, service factor,
voltage, full load current, or pretty much anything else on the label
could be significant.
Existing motor control means (contactor? - rating, overload element size,
source of control power, auxiliary contacts used/available) will also
influence your options.
All of your options could easily be botched, but one or more are
certainly viable if done correctly.
Although I am a bit rusty on the subject, I believe this will not work
with induction motors. An induction generator requires a source of (what
I think is leading) reactive power that it normally gets from the grid
it is connected to.
The torque on a 3-phase motor driven from a clean source is rather
steady. For a sing;e phase motor, the torque will pulsate. The inertia
of the load will smooth out the effects. Even a capacitor run motor will
not provide uniform torque. I suppose that might be a problem for some
delicate balancing tasks. I presume you know that there can be
instabilities in spinning devices that balancing cannot cure.
If you only had to run very light loads, a three phase motor will run
(inefficiently) on single phase if you can get it started.
Rotary converters based on standard induction motors should include
capacitors between the single phase line connected motor terminals and
the derived phase motor terminals, also sometimes a power factor
correction cap across the single phase line. One design I have seen
posted on the rec.crafts.metalworking newsgroup used a 5 HP motor with 60
uF and 50 uF capacitors to the derived phase, with an additional ~300 uF
motor start capacitor temporarily connected across the 60 uF run cap for
starting. and a 50 uF power factor cap across the line. Current and
voltage balance will never be perfect with a rotary converter based on an
induction motor with capacitors, but it is good enough to power 3-phase
motors in a home shop where the motors are not generally run continuously
at full power.
There are a number of variations on the rotary converter in use including
use of fixed capacitors large enough to start the load without a starting
capacitor, and the rope-start converter where a rope wrapped around the
motor shaft is used instead of the starting capacitor. The rope-start
version will even run and power a smaller load with poorly balanced power
without any capacitors at all; the single phase line provides enough
reactive power to keep a lightly loaded 3 phase induction motor running
once it has been started.
Better rotary converters use a special multi-tapped single phase
transformer with a non-standard induction motor winding to produce very
well balanced 3-phase power using no capacitors. This design was once
widely used in electric locomotives, and is described in detail in
"Principles of Alternating-Current Machinery" by Lawrence and Richard,
4th ed 1953 (the classic book on the subject). I don't know if these are
still made but I have seen them show up at auctions occasionally.
The static converter is a box of capacitors only, using your motor(s) for
the other half of the converter, suitable for powering motor loads only
and typically even more imbalanced that a homemade rotary converter - but
also cheaper to build yourself and often well suited for the home shop.
The VFD is also designed for driving motor loads only, and some care must
be exercised when using them with standard (not inverter rated) motors,
however if mounted very close to a 240 volt motor (short wire from
inverter to motor) or if the optional output filter is purchased with the
VFD (or better yet use the output filter and a very short cable for
minimum chance of EMI problems, possibly also use the optional VFD input
filter if sharing a power feed with sensitive loads), and the motor is
never run at reduced speeds except during ramp up to 60 Hz on start and
ramp down on stop, and good wiring practices are followed to keep VFD
noise out of the control system, then the VFD will provide the motor with
well balanced 3 phase power and operation as good as with a utility 3-
phase feed can be expected.
Can you find a surplus 3 phase motor of a larger HP size. drive it with
a smaller single phase motor (the idea is simply to run it near
synchronous speed) and supply single phase to two of the phases- and
connect all 3 phases to the balancer. This is an old farmer's trick in
rural areas where only single phase is available.
Essentially it will work- even without the capacitors -in which case an
external drive is needed to get it up to near synchronous speed. Surplus
induction motors are more readily available than synchronous machines.