Hyster A099, Troubleshooting Manual

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Group 10
Principles of Operation
Traction Motor
PRINCIPLES OF OPERATION
All electric forklift trucks covered by this manual use
three-phase alternating current (AC) induction traction
motors. AC motors are all very similar motors used
across the product line, but do vary in some ways.
This Principles of Operation will identify the significant
differences.
The AC induction motor is an electrical device which
uses an AC current provided to a wire wound stator
supplied by a DC to AC inverter to induce north and
south magnetic poles to an internal rotating device in
a controlled environment. The reaction between the
internal rotor and stator creates a push-pull effect on
the rotor causing the rotor to turn, creating a force to
do mechanical work.
In lift trucks the DC current is provided by the lead
acid battery. The DC (direct current) voltage is
changed to AC (alternating current) by the traction
motor controller. By changing the frequency of the AC
power to the motor, the motor speed can be control-
led. This job is done by the traction motor controller.
The controller also manages the direction of the motor
and thus the lift truck. It works in conjunction with the
VSM.
A speed sensor is used to detect and communicate
the speed and direction of the rotor to the controller.
This is done by sending electric pulses on two sepa-
rate channels to the controller. The controller knows
the direction of the motor by which channel’s signal it
receives first. It knows the speed by the frequency of
the pulses. The controller’s software continually moni-
tors this information. Using this feedback, the AC mo-
tor control system can provide regenerative braking,
controlled acceleration and deceleration. By changing
the frequency of the AC power to the motor, which is
also managed by the motor controller, the motor
speed can be controlled.
These AC motors have a temperature sensor built
into the stator to monitor motor temperature and pro-
vide continual temperature feedback to the thermal
management system. That system is designed to pro-
tect components from failure due to overheating. If the
motor winding temperature reaches its specified limit,
the VSM signals the traction controller to reduce the
motor performance or may even disable traction to
protect the motor. When the traction system compo-
nents are in thermal management, there is no affect
on the hydraulic system performance. The connector
for this temperature sensor is serviceable, but the
sensor itself is not.
The rotor shaft extends out each side of the traction
motor. The drive end head interfaces to the drive unit
or drive axle, depending upon configuration. For lift
trucks A935, A268, A269, and A099 a short, round
section of the shaft protrudes from the non-drive end
head of the motor. This end supports the parking
brake hub using a woodruff key and a snap ring.
There is a bearing between the motor and the parking
brake. The parking brake is replaceable.
UL safety rated EE traction motors are available as an
option on these forklifts. These motors have covered
vent holes and are only a part of the necessary equip-
ment required for the EE safety rating.
Traction motors are long life components and very
low maintenance. They have no motor brushes. The
motor bearings, rotor, stator and speed sensor are
serviceable.
Traction Motor Principles of Operation
Check the Service Manual section in Hypass Online for possible updates and check pertinent Grams
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