Datasheet

Solid State Relays Common Precautions
●Selecting an SSR for Different Loads
The following provides examples of the inrush currents for
different loads.
AC Load and Inrush Current
1. Heater Load (Resistive Load)
A resistive load has no inrush current. The SSR is generally
used together with a pulse-voltage-output in temperature
controller for heater ON/OFF switching. When using an SSR
with the zero cross function, most generated noise is
suppressed. This type of load does not, however, include
all-metal and ceramic heaters. Since the resistance values at
normal temperatures of all-metal and ceramic heaters are low,
an overcurrent will occur in the SSR, causing damage. For
switching of all-metal and ceramic heaters, select a Power
Controller (G3PW, consult your OMRON representative) with a
long soft-start time, or a constant-current switch.
2. Lamp Load
A large inrush current flows through incandescent lamps,
halogen lamps, and similar devices (approx. 10 to 15 times
higher than the rated current). 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 the
dashed line) 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.
3. Motor Load
When a motor is started, an inrush current of 5 to 10 times the
rated current flows and the inrush current flows for a longer
time than for a lamp or transformer. 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 an SSR. The
SSR may be damaged by counterelectromotive force from the
motor. Be sure to install overcurrent protection for when the
SSR is turned OFF.
4. Transformer Load
When the SSR is switched ON, an energizing current of 10 to
20 times the rated current flows through the SSR for 10 to 500
ms. If there is no load in load side circuit, the energizing
current will reach the maximum value. Select an SSR so that
the energizing current does not exceed half the inrush current
resistance of the SSR.
5. Half-wave Rectifying Circuit
AC electromagnetic counters or solenoids have built-in diodes,
which act as half-wave rectifiers. For these types of loads, a
halfwave AC voltage does not reach the SSR output. For
SSRs with the zero cross function, this can cause them not to
turn ON. Two methods for counteracting this problem are
described below.
1. Connect a bleeder resistance with approximately 20% of the
SSR load current.
2. Use SSRs without the zero cross function.
6. Full-wave Rectified Loads
AC electromagnetic counters and solenoids have built-in
diodes, which act as full-wave rectifiers. The load current for
these types of loads has a rectangular wave pattern, as shown
in the following diagram.
Accordingly, AC SSRs use a triac (which turns OFF the
element only when the circuit current is 0 A) in the output
element. If the load current waveform is rectangular, it will
result in an SSR release error.
When switching ON and OFF a load whose waves are all
rectified, use Power MOS FET Relay.
-V-model SSRs: G3F-203SL-V, G3H-203SL-V
Power MOS FET Relay: G3DZ, G3RZ, G3FM
Note. Refer to your OMRON website for detailed specification of G3FM
models.
7. Small-capacity Loads
Even when there is no input signal to the SSR, there is a small
leakage current (IL) from the SSR output (LOAD). If this
leakage current is larger than the load release current, the
SSR may fail to release. Connect a bleeder resistance R in
parallel to increase the SSR switching current.
Load
Solenoid Incandescent
lamp
Motor Relay Capacitor Resistive
load
Inrush current/
Normal current
Approx. 10
times
Approx. 10 to
15 times
Approx. 5
to 10
times
Approx. 2
to 3 times
Approx.
20 to 50
times
1
Waveform
Normal current
Inrush current
Temperature
Controller
(pulse-voltage-output)
Heater load
250
200
150
100
50
0
10 5030 100 300 500 1,000 5,000
Energized time (ms)
Non-repetitive
Repetitive
Inrush current (A. Peak)
Bleeder resistance
Load
Load
Circuit current
wave pattern
R<
E
I
L−I
E: Load (e.g., relays) release voltage
I: Load (e.g., relays) release current
Bleeder resistance R
Load power supply
Load
Bleeder resistance standards: 100-VAC power supply, 5 to 10 kΩ, 3 W
200-VAC power supply, 5 to 10 kΩ, 15 W
25