Toshiba 48-1250 A ユーザーズマニュアル
TOSHIBA - 4
TX Series
48 - 1250A
1.3 - Theory of Operation
The power of the TX Series is in the CPU, a microprocessor based
protection and control system for the motor and starter assembly.
The CPU uses Phase Angle Firing of the SCRs to apply a reduced
voltage to the motor, and then slowly and gently increases torque
through control of the voltage and current 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.
protection and control system for the motor and starter assembly.
The CPU uses Phase Angle Firing of the SCRs to apply a reduced
voltage to the motor, and then slowly and gently increases torque
through control of the voltage and current 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.
Acceleration: The TX Series comes standard with several methods of
accelerating the motor so that it can be programmed to match almost
any industrial AC motor application.
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 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 (as
per the 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.
as this has been proven 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 (as
per the 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.
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 in the TX Series provide protection
from a stall condition, an overload condition or excessive acceleration
time.
setting, the current limit setting will proportionally control the maximum
output torque. Feedback sensors in the TX Series provide protection
from 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 preset 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.
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 preset 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 current drops to running
levels, the TX Series detects an At-Speed condition and will close the
Bypass Contactor (if provided). The Bypass Contactor serves to shunt
power around the SCR stack assemblies to prevent heat build-up
NEMA 12, 3R, 4 and 4X enclosed units due to the slight voltage drop
across the SCRs. At this point, the TX Series has the motor operat-
ing at full voltage, just as any other starter would.
levels, the TX Series detects an At-Speed condition and will close the
Bypass Contactor (if provided). The Bypass Contactor serves to shunt
power around the SCR stack assemblies to prevent heat build-up
NEMA 12, 3R, 4 and 4X enclosed units due to the slight voltage drop
across the SCRs. At this point, the TX Series has the motor operat-
ing at full voltage, just as any other starter would.