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October 2004 SC2000 Manual – 177/52301 Rev G Page 29
10.1.28 Speed Limit - A traction speed limit in KPH can be set via personality 1.1.28 (0 KPH
disables the feature). As the speed of the vehicle approaches the limit, the maximum motor
voltage is reduced. If the speed limit is exceeded by more than 2 KPH (when the vehicle is
travelling down-hill for example) electrical braking will be used until the speed of the vehicle
falls to below the limit. Speed limit braking may operate in normal drive (as described
above), to increase existing braking torque if the vehicle over-speeds, or if the vehicle is
rolling in neutral.
The actual limit speed of the vehicle is typically ± 2 KPH of the personality setting,
depending on motor loading. When the feature is enabled, a probe “wire-off” feature will
limit the motor voltage if the probe is disconnected.
Calibration of the feature is made via the set menu items “Full Speed” (1.6.13) and “Probe
Frequency” (1.6.14). Full Speed should be set to the maximum speed of the vehicle,
unloaded on level ground. The Probe Frequency setting should be the output frequency of
the sensor at that speed.
The recommended sensor is an active low (i.e. NPN) inductive proximity switch. The output
is connected to connector A, pin 13. A +12V supply on connector A, pin 24 can be used for
most types of sensor. The negative supply of the sensor should be connected to the
controller’s B- terminal. Contact SEVCON for further recommendations if required.
The operation of the speed limit function can be disabled by setting personality 1.6.15 to
ON. In this situation the speed cutback 2 switch is used to enable/disable the speed limit
functionality. i.e. With speed cutback 2 not active then there is no speed limit, with speed
cutback 2 active the speed is limited to the value set in 1.1.28.
10.2 PUMP OPERATION
10.2.1 Pump Operation
- There is no start-up sequence so pulsing will be initiated after a small
delay at power-up if one or more of the pump switches is selected. There are adjustable ramp
up and ramp down delays. A Pump contactor can be specified as an option. There are
facilities for prioritising pump speeds, for having different pump speeds added together and
for having speed compensation for different load conditions.
10.2.2 Pump Speeds and Priorities
- Each of the are 7 pump switch inputs has its own speed
setting. The pump speeds are prioritised in numerical order so that Speed 1 has priority over
all other speeds and Speed 2 has priority over Speeds 3 to 7, etc. Example:- If Speed 1 is set
to 10%, Speed 2 to 20% and Speed 3 to 30% then selecting Speeds 1 and 3 will give 10%
and selecting Speeds 2 and 3 will give 20%.
10.2.3 Additive speeds
- There is also an additive feature available on pump switches 5,6 and 7
which is selected when the personality after the respective pump speed adjustment is set to
“Additive”. When this adjustment is set to “Priority” the pump speeds behave as described in
10.2.2.
The additive feature works by adding a speed selected by either pump switch 5,6 or 7 to
another selected speed to give increased power to handle the simultaneous pump
operations.
Example:- If speed 2 is set to 40% speed 5 is set to 25%, and speed 6 is set to 10%, then
selecting all 3 switches will give a demand of 75%. whilst selecting only speeds 2 and 5
would give 65%.
10.2.4 Pump accelerator input
- The pump accelerator demand is associated with Speed 1. The
pump will operate at the Creep Speed setting when the accelerator is at minimum demand
and change linearly to Speed 1 as the accelerator is increased to the maximum demand. The
pump pot accelerator input can be connected and adjusted as per the previously described
traction accelerator input.(9.1.18).
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