1. Why do some of your PMG models
output a at higher voltages which is not compatible for
direct battery charging?
Ans: This is due to the fact that operating at higher
voltages result in lower currents. This in turn results
in lower resistive losses which is an unavoidable fact
at the moment. Components and wires all become cheaper
for both the PMG and any connected equipment (especially
for higher powered units). With reduced losses, the units
can operate with higher efficiency. In fact, our grid
tie inverters and PMGs have been designed to complement
each other in terms of power and output voltage range.
2. Is PMG the only thing to
consider for a wind turbine?
Ans: No, all the major components of the wind turbine
has to be considered when designing or buying a good
system. The blades set has to be of a good design to
maximise the capture of wind energy. The yaw has to
be designed properly to protect the system while still
maximising energy capture. The overall system has to
be strong enough and yet light enough. The electronics
have to be of a smart design if possible to maximise
the energy conversion / transfer / storage. However,
the PMG is a major link in the chain and any weak link
in the chain would mean a reduced efficiency of the
unit.
3. Why the pmg for wind is different
from the traditional pmg?
Ans: The important issues are that PMGs for wind turbines
are used in a different location and used in a different
way. Wind turbines are driven by wind driving a set
of blades not by a machine which has a reasonable amount
of torque. Thus, the starting torque of the PMG has
to be low in order for the blades to turn at a reasonably
low wind speed. Otherwise the turbine will miss out
on all the energy at low winds which is present most
of the time. It is also working in a harsh environment
at heights which is not easily accessbily. Thus, the
design has to be reliable and robust enough to withstand
what the environment has to throw at it, wide temperature
range, humidity, UV exposure etc. If the components
used are sub-standard, this will result in down time
(worse if the turbine is remotely located which means
no one will know about the failure) and maintenance.
Use of good components, will result is less frequent
down time and less frenquent maintenance which is a
cost savings at the end of the day for both the end-user
and the wind turbine manufacturer.
4. Why does the PMG need to
be strong?
Ans: In most wind turbine designs, the PMG is an integral
part of the wind turbine structure. which means that
the PMG has to support the weight and all the forces
that are experienced by the turbines in strong winds,
turbulant winds and high yaw rates. If the PMG is not
strong enough to withstand these forces, the PMG might
easily break apart and part of the wind turbine might
fall off and hurt people, lifestock or damage surrounding
properties. For example if the shaft used is not strong
thick or strong enough to withstand the yaw forces,
it might snap in strong turbulent winds and the blades
might fly off and hurt someone as a result.
5. Why does a slightly little
higher initial investment benefits in terms of future
maintenence cost of wind turbine?
Ans: An slightly higher investment into a better product
right at the start of the project will bring about lower
down time (as explained above), reduce costs in terms
of calling out an engineer to replace or service parts,
lower risks, better energy capture etc. If the PMG fails,
the turbine will have to be brought down, tested, replaced
(which is expensive) or repaired (also expensive) and
re-commissioned again. If this is happening because
of the manufacturer using a cheap component, then the
costs to the end-user does not make sense. A wind turbine
is an investment to last a long time. Not like a CD
player to be thrown away when a part fails because it
is cheaper to buy a new one than to repair it. The cost
of a PMG is not significatn when compared to the costs
of other parts, installation, electronics, etc.
6. How do you reduce the starting
torque?
Ans: This is a complicated technical question which
has no simple answer. Part of the solution lies with
the internal design of the PMG, the windings and the
magnets. Part of the answer lies with the mechanical
design of the PMG covers and bearings. A major contributing
factor is the high quality control employed during the
manufacture of the unit. A design is only as good as
the quality control behind the manufacturing process.
Some of the design to reduce starting torque needs high
tolerance and precision during manufacture in order
to reduce the starting torque and maximum performance.
Therefore, this is a problem that is usually difficult
to solve unless the manufacturer has a good knowledge
and experience in this field.
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