Publication 700-AT001A-EN-E June 2002
2-8
Considerations When Designing SSR Control Systems
and ceramic heaters are low, an overcurrent will occur in the SSR,
causing damage. For switching of all-metal and ceramic heaters, select
a constant-current type SSR.
/DPS/RDG
Large inrush current flows through incandescent lamps, halogen
lamps, and so on (approx. 10…15 times higher than the rated current
value). Select an SSR so that the peak value of inrush current does not
exceed half the inrush current resistance of the SSR. Refer to
“Repetitive” (indicated by dashed lines) shown in the following figure.
When a repetitive inrush current of greater than half the inrush current
resistance is applied, the output element of the SSR may be
damaged.(Refer to Q37 in Q&A Section.)
If a SSR is used to switch a fluorescent lamp, the waveform of the
power supply voltage will be distorted, and flickering will occur.
Fluorescent lamps are discharge tubes, and have transformers for
producing high voltages. For this reason, noise and harmonics are
generated as a result of distortions in the power supply voltage, small
phase gaps, and differences in positive and negative ON-voltages.
0RWRU/RDG
When a motor is started, an inrush current of 5…10 times the motor’s
rated current flows and the inrush current flows for a period
approximately 50% longer than a lampload In addition to measuring
the startup time of the motor or the inrush current during use, ensure
that the peak value of the inrush current is less than half the inrush
current resistance when selecting a SSR. The SSR may be damaged by
counter-electromotive force from the motor. So when the SSR is
turned OFF, be sure to install overcurrent protection.
Temperature
Controller
(voltage-output
type)
Heater load
Input
Output
Non-repetitive
Repetitive
Inr
ush current (A.
P
eak)
Power supply time (ms)
