(TITLE)
Magnetic Levitation
(INTRODUCTION)
Exploring design points for suspending
heavy loads when permanent magnets are suspended in the air by the attractive
force of electromagnets.
(METHODS)
(1) Fig.1 shows the overall configuration.
F1 (attractive force) and F2 (gravity
force) are
When F1=F2, the permanent magnet floats in
the air.
Electromagnet is an iron core with windings.
A power supply Vc and a switch SW1 are connected in series. When SW1 is ON, the pole is
magnetized to the south pole and F1 becomes large.
Also, F2 increases because the iron core is
not magnetized when SW1 is OFF.
The position at which the permanent magnet
floats in the air at only one point is when the distance shown is D. When
F2>F1, the distance becomes D+ΔD ,and the permanent magnet falls.
When F2<F1, the distance becomes D-ΔD ,and
the permanent magnet is attracted to the electromagnet. The control is such
that a magnetic sensor detects the magnetic flux density and an electronic
circuit (not shown) turns SW1 on and off at high speed to keep the distance D ,and
the permanent magnet floats in the air.
Fig.1
(2) Fig.2 shows the data related to the magnetic sensor.
①
B(mT):
The magnetic flux density B (mT) is shown when the probe of tesla meter is placed at the position of the magnetic sensor and a permanent magnet (φ20 x 10, 2 pieces) is placed at a distance D (mm). Regarding the sensitivity, the closer the permanent magnet and the iron core are, the more non-linear the B(mT) increases.
②Vh (mV) AH3503:
LINIEAR HALL-EFFECT SENSOR
Built-in amplifier
Manufacturer: NANJING AH ELECTRONICS
CO.,LTD
Sensitivity : 7.5~17.5(mV/mT)
It can be seen that the sensor output is
magnetically saturated at D=20 (mm).
That is, when B > 100 (mT), it becomes
uncontrollable.
③Vh (mV) HG-166A:
GaAs Hall-ELEMENT
no amplifier
Manufacturer: ASAHI KASEI MICRODEVICES
Vh=78~102(mV) (Conditions) B=50(mT), Vc=6V
Magnetic saturation does not occur even
when D=2 (mm).
④Vh (mV) HG-166A (Av=5)
Characteristics when amplification = 5
At D=2 (mm), magnetic saturation does not
occur, so control is possible.
Fig.2
(RESULTS)
In order to suspend a heavy load in the
air, it is important that the magnetic sensor does not become magnetically
saturated at high magnetic flux densities.
Commercially available Hall ICs that have
an amplifier built into the Hall IC have about twice the sensitivity due to
manufacturing variations, so even if ICs with the same product name are used,
magnetic saturation may or may not occur, so use is not recommended.
Recommended magnetic sensor does not magnetically saturate even at B = 300 (mT) .
(DEMO)
The globe weighs 358g.
