IAI PSA-24, Instruction Manual

Page: 48 / 84

4.1 Specification Details
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Inrush current prevention circuit
This power supply unit uses a thermistor to suppress inrush current at startup. The thermistor
has high resistance at low temperatures and low resistance at high temperatures. Therefore,
when the power is turned on, the inrush current is suppressed by the high resistance, but as
power is supplied the temperature rises and the resistance decreases, reducing the loss due to
the thermistor.
Always note the following points due to the above characteristics.
● At low temperatures, the resistance of the thermistor is large, which may cause startup
malfunction issues. When starting multiple controllers at the same time in a low temperature
environment, startup malfunctions are less likely to occur if the inrush current is dispersed by
shifting the timing at which the servos turn ON.
● If the input voltage is turned ON again before the power supply temperature drops sufficiently,
the input voltage will be applied while the thermistor resistance is still low and a large inrush
current will flow. Therefore, after turning OFF the input voltage, wait about 30 minutes for
cooling before turning ON the input power again.