Datasheet

Solid State Relays Common Precautions
3. ON/OFF Frequency
An SSR has delay times called the operating time and release
time. Loads, such as inductive loads, also have delay times
called the operating time and release time. These delays must
all be considered when determining the switching frequency.
4. Input impedance
In SSRs which have wide input voltages (such as G3CN and
G3TB), the input impedance varies according to the input
voltage and changes in the input current.
For semiconductor-driven SSRs, changes in voltage can
cause malfunction of the semiconductor, so be sure to check
by the actual device before usage.
See the following examples.
Input impedance (Example)
G3CN
■Output Circuit
●AC Switching SSR Output Noise and Surges
x In case there is a large voltage surge in the AC current being
used by the SSR, the RC snubber circuit built into the SSR
between the SSR load terminals will not be sufficient to
suppress the surge, and the SSR transient peak element
voltage will be exceeded, causing overvoltage damage to the
SSR.
x Only the following models have a built-in surge absorbing
varistor: G3NA, G3S, G3PA, G3NE, G3PH, G3DZ (some
models), G3RZ, and G3FM. When switching an inductive load
with any other models, be sure to take countermeasures
against surge, such as adding a surge absorbing element.
x In the following example, a surge voltage absorbing element
has been added.
Select an element which meets the conditions in the following
table as the surge absorbing element.
●Output Connections
Do not connect SSR outputs in parallel. With SSRs, both sides of
the output will not turn ON at the same time, so the load current
cannot be increased by using parallel connections.
●DC Switching SSR Output Noise Surges
When an L load, such as a solenoid or electromagnetic valve, is
connected, a diode that prevents counter-electromotive force. If
the counter-electromotive force exceeds the withstand voltage of
the SSR output element, it could result in damage to the SSR
output element. To prevent this, insert the element parallel to the
load, as shown in the following diagram and table.
As an absorption element, the diode is the most effective at
suppressing the counter-electromotive force. The release time
for the solenoid or electromagnetic valve will, however, increase.
Be sure to check the circuit before use. To shorten the time,
connect a Zener diode and a regular diode in series. The release
time will be shortened at the same rate that the Zener voltage
(Vz) of the Zener diode is increased.
Talbe 1. Absorption Element Example
(Reference)
1. Selecting a Diode
Withstand voltage = V
RM ≥ Power supply voltage × 2
Forward current = I
F ≥ load current
2. Selecting a Zener Diode
Zener voltage = V
Z < SSR withstand voltage
− (Power supply voltage + 2 V)
Zener surge power =
P
RSM > VZ × Load current × Safety factor (2 to 3)
Note. When the Zener voltage is increased (Vz), the Zener diode capacity
(P
RSM) is also increased.
●AND Circuits with DC Output SSRs
Use the G3DZ relay for the following type of circuit.
●Self-holding Circuits
Self-holding circuits must use mechanical relays. (SSRs cannot
be used to design self-holding circuits.)
Voltage Varistor voltage Surge resistance
100 to 120 VAC 240 to 270 V
1,000 A min.200 to 240 VAC 440 to 470 V
380 to 480 VAC 820 to 1,000 V
20
0
8
6
4
3
2
1.5
213468102030
Input voltage (V)
Input impedance
T=+25°C
Input current (mA)
Input impedance (kΩ)
Input current
Varistor
Load
Varistor
Absorption
element
Diode
Diode +
Zener diode
Varistor CR
Effectiveness
{{U ×
INPUT
Load
SSR
Input Output
Input of the
logic circuit
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