Automationdirect.com Stellar SR44, User Manual

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Chapter 3: Applications
3.5 – Chapter 3 Glossary of Terms
Breakaway Torque The minimum torque required to achieve rotor movement for the motor with
its load.
Current Limit The current at which the ramp is held. For the SR44, current limit is only
active during start-up where it contributes to the motor control function.
This feature is particularly useful when starting high-inertia loads that require
an extended start-up period. (See also Overload Level.)
Direct-On-Line (DOL)The direct connection and disconnection of a motor from the AC main
supply by means of a contactor or switch. Acceleration and operation is at
full mains voltage only.
Inrush Current or Locked Rotor Current
The current that flows at the instant of connection of a motor to the power
source. It is limited by the impedance presented by a de-energized motor
and the applied voltage. Usually expressed as a multiple of motor full-load
current.
Kick-start Voltage The percentage of supply voltage applied before commencing ramp-up
when a load has a high breakaway torque and the standard settings of
pedestal voltage may not allow sufficient torque to be developed by the
motor to cause acceleration.
Overload Level The level of current at which the controller overload begins to integrate. For
the SR44, the overload detector is always active and provides protection
against prolonged over-current operation.
Pedestal Voltage The voltage that the unit applies to the motor at start-up. It is expressed as a
percentage of the rated supply voltage.
Power Factor The ratio, expressed as a trigonometric cosine, of the real power
consumption to the apparent power consumption.
Top of Ramp (TOR) The unit achieves Top of Ramp (TOR) when it completes the start-up stage of
motor control. (This occurs when the voltage applied to the motor first
equals the main supply voltage.)
Soft-start The regulation by electronic means, of the supply voltage from an initial low
value to full voltage during the starting process. This over-comes the
inherent drawbacks of a switched supply. The motor torque is modified in
proportion to the square of the voltage applied.
Trip A trip occurs when the unit removes power to the motor because its
operation equals the limit imposed by one of its self-protection features.
SR44 Series Soft Starter User Manual
1st Ed, Rev B 07/31/2019
3–20