FAQ No. FAQ02152
Question
Are Solid-state Relays (SSRs) unable to
switch microloads?
Answer
The minimum load currents in the following table can be switched using
SSRs with Power MOS FET outputs (G3DZ/G3RZ).
Minimum Load Currents for G3DZ and G3RZ
|
Load voltage |
G3DZ |
G3RZ |
| 200 VAC |
100 µA |
100 µA |
| 100 VAC |
10 µA |
100 µA |
The following applies to AC SSRs with triac or thyristor outputs and to DC
SSRs with power transistor outputs.
SSRs with AC Output:
At present, the minimum load current for most SSRs is 100 mA (50 mA at an
ambient temperature of 25°C or higher) considering the degree of current
(holding current) required because of problems with the load failing to
reset due to leakage current and the output elements remaining ON.
Microloads below these values can be supported by connecting bleeder
resistance in parallel with the load. By using MOS FETs, however,
microloads can be directly switched without bleeder resistance.
Bleeder Resistance
| 100 VAC |
5 to 10 kΩ |
3 W |
| 200 VAC |
5 to 10 kΩ |
15 W |
SSRs with DC Output:
Leakage current may cause the load to fail to reset.
There is generally no problem for most microload switching with SSR models
with a leakage current of 0.1 mA or less. Caution is required, however,
for SSR G3CN-D, G3FD,
G3HD and other models with large leakage current.
The following table provides a rough guide to bleeder resistance if reset
failure occurs using the G3CN-D, G3FD, or G3HD.
Bleeder Resistance
| 5 VDC |
1.6 kΩ |
1/4 W |
| 12 VDC |
620 Ω |
1 W |
| 24 VDC |
330 Ω |
5 W |
Other Solid-state Relay
FAQs
 What is the difference between triacs and thyristors?
The SSR does not turn OFF. What is causing this and what can be done about it?
Can the output sides of SSRs be connected in series?
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