Toshiba VF010H05 - Manual (Page 16)

JKSSS+ Series - 10
JKSSS+ Series 2.3 - 4.2KV
· RTD Input: Will bias the register in either direction based on real-time input of
the motor, bearing and even ambient temperature conditions.
· Dynamic Reset is another feature that adds reliability and consistency to the
performance of the soft starter. If a motor overload condition occurs and the soft
starter trips, it cannot be reset until sufficient cool down time has elapsed. This
cool down time is determined by the thermal state of the motor when it tripped
(i.e. hot motors cool more quickly due to additional convection). The cool down
time is also biased by RTD measurements when used.
· Retentive Memory provides continuous overload protection and real time
reset even if power is lost. Upon restoration of power, the soft starter will
read the Real Time Clock and restore the thermal register to what it should be
given the elapsed time.
· Learned Reset Capacity is a feature that is unique to the JKSSS+ Series. By
sampling the amount of thermal capacity used in the previous three successful
starts, the soft starter will not allow a reset until a sufficient amount of thermal
capacity has been regained in the motor. This prevents nuisance tripping and
insures that unsuccessful start attempts (which would otherwise use up the
starts-per-hour capacity of the motor) are not counted.
1.8 Firing Circuit
The SCR gate firing circuit is critical to performance and stability of the system.
The firing circuit includes several unique features which enhance the ruggedness,
noise immunity and flexibility for maximized performance. In most applications, this
performance is attained without the need for reactors or field installed devices. These
features include:
Auto Synchronizing of the gate timing pulses match each phase firing angle
to their respective phases. The starter actively tracks minor shifts in the line fre-
quency, avoiding nuisance tripping that may happen with conventional gate firing
systems. This is especially useful on portable or backup generator supplies,
allowing the starter to be used confidently in applications that have unstable
power .
Sustained Pulse firing keeps the firing signal active for 270 electrical degrees,
ensuring that the DC gate pulse causes the SCR to fire even if line noise is
present at a critical moment. This provides the soft starter with superior noise
immunity and protects against misfiring, enhancing the system reliability.
Closed Loop Firing Control is a method of balancing the SCR firing pattern
based on the desired output. The CPU uses feedback signals from both the
output current and voltage providing smooth output and preventing imbalances
during ramping which prevents unnecessary motor heating .
Transformer Isolation of the firing signals prevents interference from line noise
and EMI/RFI signals that may be present. Specially designed 120V 3 phase iso-
lation transformers provide potential measurement, firing board power and gate
power systems while being isolated from the line voltage. High isolation Ring
Transformers are used to step this down to 28Vac for the Sustained Pulse firing
circuit, providing further isolation for the SCR gates.
Fiber Optic Isolation is provided for all signal interfaces between the Medium
Voltage and Low Voltage systems. Even the current signals from CTs are con-
verted to fiber optic signals for maximum isolation and safety.