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Basic Installation and Operation
Guide
Removable conduit entry plates are provided in the bottom of the enclosures to facilitate drilling and punching of conduit holes
without exposing the equipment to contamination from metal debris.
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Enclosure Finish: The enclosure is suitable for use in noncorrosive environments. The paint is ANSI 61 gray polyurethane
powder over a zinc phosphate pretreatment with a minimum thickness of 2 mil. 11 gauge steel is used in all enclosures. All
NEMA 1 & 12 units have bottom entrance plates.
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Lifting Provisions: Eyes or angles capable of supporting the maximum weight of each shipping split are provided on the
top of the enclosure.
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Power Bus: Optional main horizontal phase bus bars can be configured to extend the entire length of the starter lineup. Bus
bar material is tin-plated or silver-plated copper. All bus ratings are per UL Standard 347.
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Bracing: Bus bars are braced with non-tracking fire resistant non-hygroscopic insulation supports and have a minimum fault
current rating of 50,000 Amps.
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Connections: All bus connections use 2 bolts minimum, with Belleville spring washers to ensure tightness. Splice kits for
each shipping split are included, along with specific installation instructions.
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Ground Bus: A continuous ground bus bar with a minimum rating of 400 Amps extends the entire length of the starter near
the bottom of each enclosure. A grounding strap connects each vertically adjacent compartment and also ties the grounding
arm of the disconnect switch to the main ground bus bar (see section 2.8).
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Seismic Qualifications: The entire starter assembly, when properly installed, withstands vertical and horizontal
accelerations typical of seismic Zones 1 through 4 as defined in the UBC. The assembly will not overturn or show significant
lateral movement, but cannot be expected to continue operating during, or after, a seismic event.
1.5 Theory of Operation
The soft starter is CPU controlled, using a microprocessor based protection and control system for the motor and
starter assembly. The CPU uses Phase Angle Firing control of the SCRs to apply a reduced voltage to the motor,
and then slowly and gently increases torque using voltage and current control until the motor accelerates to full
speed. This starting method lowers the starting current of the motor, reducing electrical stresses on the power
system and motor. It also reduces peak starting torque stresses on both the motor and load mechanical
components, promoting longer service life and less downtime.
1.5.1 Acceleration:
The soft starter comes standard with several methods of accelerating the motor so that it can be programmed to
match almost any industrial AC motor application. The factory default setting applies a Voltage Ramp with
Current Limit as this has been proven to be the most reliable starting method for the vast majority of
applications. Using this starting method, the Initial Torque setting applies just enough voltage to the motor to
cause the motor shaft to begin to turn. This voltage is then gradually increased over time (Ramp Time setting)
until one of three things happen: the motor accelerates to full speed, the Ramp Time expires, or a Current Limit
setting is reached. If the motor accelerates to full speed before the ramp time setting has expired, an automatic
Anti-oscillation feature will override the remaining ramp time and full voltage will be applied. This will prevent any
surging or pulsation in the motor torque, which might otherwise occur due to the load not being fully coupled to
the motor when operating at reduced voltage and torque levels. If the motor has not reached full speed at the end
of the ramp time setting, the current limit setting will proportionally control the maximum output torque. Feedback
sensors provide protection against a stall condition, an overload condition, or excessive acceleration time.
The Current Limit feature is provided to accommodate installations where there is limited power available (for
example, on-site generator power or utility lines with limited capacity). The torque is increased until the motor
current reaches the pre-set Current Limit point and it is then held at that level. Current Limit overrides the ramp
time setting so if the motor has not accelerated to full speed under the Current Limit setting, the current remains
limited for as long as it takes the motor to accelerate to full speed. When the motor reaches full speed and the
TOSHIBA
JKSSS Series Solid State Soft Starters
5
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