Section 8. Theory of Operation Model 8210/8250 Maintenance Manual
Definitions
8-4 Publication: 1146945/001, Revised: 25 Sep 2018
Short Circuit or “Short”
A short circuit is an unspecified path in a
circuit that provides unwanted full or partial
continuity between two or more locations in an
electrical circuit.
Example 1: Two insulated wires are physically
next to each other and the insulation has worn
off each of the wires. Because the conductors
are now touching each other, there is a short
circuit.
Example 2: A power cable from the battery to a
junction post in the truck has had the
insulation worn away. Because the wire
conductors are touching the tractor frame,
there is a short circuit of the battery cable.
Speed Limiting
The Vehicle Manager limits the maximum
speed. The “Max speed, Walking Mode”
parameter determines the maximum speed
value sent by the VM to the traction amplifier
(max. PWM) for the two directions of travel while
in travel mode. This is a programmable
parameter.
Static Return to Off (SRO)
The SRO feature prevents starting the truck
(direction selected) prior to the release of the
brake. SRO examines sequencing of the brake
(deadman) switch input and key switch input
relative to the direction input. The switch must
be activated before the directional/speed
control is rotated. If a direction is selected
before or simultaneously (within 50 ms) with
the brake input, the TA does not command
travel.
Thermal Cutback (Traction
Amplifier)
Thermal cutback of the traction amplifier is
below –13°F (–25°C) or above 185°F (85°C). At
185 to 203°F (85 to 95°C), the drive current
limit is linearly decreased from full set current
down to zero. At –13 to –40°F (–25 to –40°C), the
current limit is reduced to approximately half
the set current, resulting in reduced travel
speed. Below –40°F (–40°C) or above 203°F
(95°C), the allowed travel speed is zero percent.
This function sets code C43 on the display
when a thermal cutback condition occurs. It
may also be a factor when codes C44 and C46
occur.
Tractor
The body section of the truck that contains the
motors, drive unit, controls, and handle.
Truck Off Delay (Keypad only)
This delay sets the truck OFF delay time (energy
saving feature). If this time delay passes while
the truck is in a brake position and the truck is
idle (no inputs requested), the Vehicle Manager
powers the truck OFF. This is a programmable
Driver parameter setting that ranges from 0 to
20 minutes. When the parameter is set to 0, or
the truck has the key switch, the truck never
powers OFF. See “Programming Truck
Parameters” on page 3-6.
Undervoltage Cutoff
Undervoltage protection automatically occurs
when there is very low voltage (less than 13V) at
the traction amplifier TA B+ connection. Code
C41 is displayed and the truck must be
restarted.
Vehicle Manager
Programmable motor control functions are
performed by the electronic circuitry (VM)
housed within the control handle. See “Vehicle
Manager” on page 8-6.
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