© Mitsubishi Forklift Trucks 2013. All
© Mitsubishi Forklift Trucks 2013. All rights reserved.rights reserved. Revision: BRevision: B
Document ID: 615023Document ID: 615023
76 (244)76 (244)
PBV20N2 PBV20N2 Service Service ManualManual
6.56.5 TractionTraction
The movement of the truck is The movement of the truck is controlled by the traction controller. Before the truck cancontrolled by the traction controller. Before the truck can
be driven, the battery must be be driven, the battery must be connected, the main key switch must be closed and theconnected, the main key switch must be closed and the
system must have system must have passed the self-test procedure.passed the self-test procedure.
When the truck is When the truck is powered on and in the standby mode, it can powered on and in the standby mode, it can be driven by turning thebe driven by turning the
accelerator at the end of the accelerator at the end of the tiller arm forward or tiller arm forward or backward. In the electrical schematicbackward. In the electrical schematic
diagram, the accelerator is presented in zones 12 to 15 diagram, the accelerator is presented in zones 12 to 15 on page 3 of the on page 3 of the electricalelectrical
schematic diagram. The acceleratoschematic diagram. The accelerator unit receives its r unit receives its positive 24 volt electrical supplypositive 24 volt electrical supply
from the pin 2 of the connector XA1C. The negative connection is supplied directly fromfrom the pin 2 of the connector XA1C. The negative connection is supplied directly from
- B. - B. When the accelerator is turned forward or backward, it When the accelerator is turned forward or backward, it indicates the direction to theindicates the direction to the
traction controller via the pins 4 traction controller via the pins 4 and 8 of the and 8 of the connector XA1B. It also provides a varyingconnector XA1B. It also provides a varying
voltage to the pin 4 voltage to the pin 4 of the connector XA1C. The voltage varies between 0, 3 of the connector XA1C. The voltage varies between 0, 3 and 4.7and 4.7
volts, depending on the position of the accelerator control. The voltage increases as thevolts, depending on the position of the accelerator control. The voltage increases as the
accelerator is moved to either extreme.accelerator is moved to either extreme.
6.66.6
AC motor operationAC motor operation
In the induction motor (= In the induction motor (= asynchronoasynchronous motor), the stator us motor), the stator is powered with alternatingis powered with alternating
current and designed to create a rotating magnetic field, which rotates in current and designed to create a rotating magnetic field, which rotates in time with thetime with the
AC oscillations. In AC oscillations. In the induction the induction motor, the rotomotor, the rotor rotates at a slower rotates at a slower speed than tr speed than thehe
stator field and therefore the magnetic field through the rotor is stator field and therefore the magnetic field through the rotor is changing (rotating). Thechanging (rotating). The
rotor has windings in the form rotor has windings in the form of closed wire loops. The rotating magnetic flux inducesof closed wire loops. The rotating magnetic flux induces
currents in the rotor windings as currents in the rotor windings as in a transformer. These currents in turn in a transformer. These currents in turn createcreate
magnetic fields in the rotor that magnetic fields in the rotor that interact with the stator field. Due interact with the stator field. Due to Lenz's law, theto Lenz's law, the
direction of the created magnetic field is such direction of the created magnetic field is such as to oppose the change in currentas to oppose the change in current
through the windings. The cause of induced current in the rotor through the windings. The cause of induced current in the rotor is the rotating statoris the rotating stator
magnetic field, so to oppose it, this rotor starts to rotate in the direction of the rotatingmagnetic field, so to oppose it, this rotor starts to rotate in the direction of the rotating
stator magnetic field to make the relative speed between the rotor stator magnetic field to make the relative speed between the rotor and the rotatingand the rotating
stator magnetic field zero.stator magnetic field zero.
For these currents to be For these currents to be induced, the speed of the physical rotor must induced, the speed of the physical rotor must be lower thanbe lower than
that of the stator's that of the stator's rotating magnetic field or the magnetic field would not be movingrotating magnetic field or the magnetic field would not be moving
relative to the rotor relative to the rotor conductors and no currents would be induced. As the speed of theconductors and no currents would be induced. As the speed of the
rotor drops below synchronous speed, the rotation rate of the magnetic field in rotor drops below synchronous speed, the rotation rate of the magnetic field in the rotorthe rotor
increases, inducing more current in the windings and creating more torque. The ratioincreases, inducing more current in the windings and creating more torque. The ratio
between the rotation rate of the magnetic field as between the rotation rate of the magnetic field as seen by the rotor (sseen by the rotor (slip speed) and thelip speed) and the
rotation rate of the stator's rrotation rate of the stator's rotating field is called "slip". Under load, the otating field is called "slip". Under load, the speed drops andspeed drops and
the slip increases enough to create sufficient torque to turn the slip increases enough to create sufficient torque to turn the load. For this reason,the load. For this reason,
induction motors are sometimes referred to induction motors are sometimes referred to as asynchronous motors. An as asynchronous motors. An inductioninduction
motor can be used as motor can be used as an induction generatoan induction generator, or r, or it can be unrolled to form it can be unrolled to form the linearthe linear
induction motor, which can directly induction motor, which can directly generate linear motion.generate linear motion.
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