Electricity: single generator systems – Automatic control of generator or driving means – Electrical conditions in circuit other than that of...
Reexamination Certificate
2002-02-12
2003-05-27
Lam, Thanh (Department: 2834)
Electricity: single generator systems
Automatic control of generator or driving means
Electrical conditions in circuit other than that of...
C322S046000, C322S029000, C310S06800R
Reexamination Certificate
active
06570365
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a device capable of increasing the rotation speed of a magneto motor and, more particularly, to a plurality of sets of magnetic sensors provided in a magneto motor to sense rotary pole variation of a permanent magnet of the rotor and let exciting coils of the stator have different conduction time differences and torsion coefficients K
T
of different strengths so that the same motor can generate various kinds of different rotation speeds.
BACKGROUND OF THE INVENTION
To manufacture an electromotor of high operational efficiency, an appropriate value of the torsion coefficient K
T
must be designed and matched with the operational range of the electromotor, as illustrated with the following formulas.
E=K
E
·&OHgr;
K
E
=B·D·L·Z/
2
T=K
T
·I
a
K
T
=B·D·L·Z/
2
wherein E is the counter electromotive force voltage (volt), T is the output torsion (N−m), K
E
is the counter electromotive force coefficient, K
T
is the torsion coefficient, &OHgr; is the rotation speed of the armature (rad/sec), I
a
is the armature current (ampere), B is the magnetic flux density of the gap (gauss), D is the outer diameter of the armature (cm), L is the superimposed thickness (cm), and Z is the total number of turns of conductors.
As can be seen from the above formulas, the counter electromotive force coefficient K
E
equals the torsion coefficient K
T
, and the counter electromotive force coefficient K
E
is inversely proportional to the rotation speed of the armature &OHgr;. Therefore, for a fixed counter electromotive force voltage E, if the normal rated rotation speed of the armature &OHgr; is lower, the value of the counter electromotive force coefficient K
E
will be relatively higher, while if the normal rated rotation speed of the armature &OHgr; is higher, the value of the counter electromotive force coefficient K
E
will be relatively lower. If a motor is designed to have a higher normal rated rotation speed of the armature &OHgr;, the value of the torsion coefficient K
T
will be relatively lower so that the torsion T (T=K
T
·I
a
) can only be increased with a higher armature current I
a
if the motor is operated at a lower rotation speed. If a motor is designed to have a higher torsion coefficient K
T
, the motor will not accomplish a higher normal rated rotation speed &OHgr; because K
T
=K
E
and E=K
E
·&OHgr;.
The present invention can let a motor have a higher torsion coefficient K
T
. Moreover, the present invention can switch to magnetic sensors sensing angle in advance to let the armature of the motor generate the effect of weak magnetic control, hence reducing the magnetic flux density of the armature gap. From the above formulas K
E
=B·D·L·Z/2 and E=K
E
·&OHgr;, because the magnetic flux density B of the armature gap decreases, the counter electromotive force coefficient K
E
consequentially decreases. Therefore, the rotation speed of the armature, &OHgr;, will inevitably increase.
The torsion coefficient K
T
of the prior art motor is a single value. For a motor usually operating in the range of lower rotation speeds and sometimes operating in the range of higher rotation speeds (e.g., a light electric vehicle), in order to let the motor operate in the seldom work range of the highest rotation speed when necessary, because K
E
=K
T
, E=K
E
·&OHgr;, and T=K
T
·I
a
, the torsion coefficient K
T
and the counter electromotive force coefficient K
E
must decrease for increasing the rotation speed &OHgr; to the seldom work range of the highest rotation speed if the counter electromotive force voltage E is fixed. Because the torsion coefficient K
T
decreases, and the motor usually operates in the range of lower rotation speeds, the armature current I
a
must increase to increase the torsion T because T=K
T
·I
a
. However, a too large I
a
is not good to the operational efficiency of the motor. This can be known from the following formula.
P=I
2
·R
wherein P is the dissipated power of the coil of an electromotor, I is the armature current, and R is the impedance of the coil. Therefore, if the torsion of a motor is increased by increasing the armature current, the dissipated power of the stator coil will increase squarely, and heat will be generated in the impedance of the coil. The impedance of the coil will correspondingly rise due to the temperature rise of the metallic coil. This vicious circle will let the motor operate in an environment of high temperature, hence resulting in a worse output efficiency.
SUMMARY OF THE INVENTION
A stator portion of a conventional motor is formed by winding a single coil. Therefore, the torsion coefficient K
T
and the counter electromotive force coefficient K
E
thereof are consequentially constant values. If a motor is designed to have higher values of the K
T
and K
E
, the rotation speed of the armature, &OHgr;, will decrease proportionally. In the present invention, a plurality of sets of magnetic sensors are provided in a magneto motor to sense rotary pole variation of a permanent magnet of the rotor. A set of magnetic sensors is provided at the position of the stator portion letting the difference between the conduction time of the stator's exciting coil and the rotary pole variation time of the rotor be zero or lower so that the motor can generate the strongest or stronger torsion coefficient K
T
. Another set of magnetic sensors is provided at the position of the stator portion letting the difference between the conduction time of the stator's exciting coil and the rotary pole variation time of the rotor be longer so that the motor can generate a phenomenon similar to weak magnet control. Detection signals of the magnetic sensors are controlled by a magnetic detection signal selection circuit, and are integrated to output a detection output signal to a motor drive and control circuit, which lets the stator portion and the magneto rotor portion generate armature reactions of different strengths.
The above weak magnetic control device capable of increasing the rotation speed of a motor when necessary can let the motor have a larger torsion coefficient K
T
. When a motor of larger K
T
value operates at lower rotation speeds, because the armature current I
a
can be decreased proportionally (T=K
T
·I
a
), the dissipated power of the stator coil of the motor will also decrease (P=I
2
·R), thereby reducing the working temperature of the motor and increasing the operational efficiency of the motor operating at lower rotation speeds.
The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawing, in which:
REFERENCES:
patent: 5469005 (1995-11-01), Asama et al.
patent: 5550457 (1996-08-01), Kusase et al.
patent: 6114785 (2000-09-01), Horng
patent: 6249067 (2001-06-01), Schob et al.
patent: 6285101 (2001-09-01), Kazama et al.
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