Precautions for Correct Use of SSRs

Before Actual Operation

1. The SSR in operation may cause an unexpected accident. Therefore it is necessary to test the SSR under the variety of conditions that are possible. As for the characteristics of the SSR,it is necessary to consider differences in characteristics between individual SSRs.

2.The ratings in this catalog are tested values in a temperature range between 15°C and 30°C, a relative humidity range between 25% and 85%, and an atmospheric pressure range between 88 and 106 kPa. It will be necessary to provide the above conditions as well as the load conditions if the user wants to confirm the ratings of specific SSRs.

Input Circuit

Input-side Connection

There is variation in the input impedance of SSRs. Therefore, do not connect multiple inputs in series. Otherwise malfunction may occur.

Input Noise

SSRs need only a small amount of power to operate. This is why the input terminals must shut out electrical noise as much as possible.
Noise applied to the input terminals may result in malfunction. The following describes measures to be taken against pulse noise and inductive noise.

1.Pulse Noise
A combination of capacitor and resistor can absorb pulse noise effectively. The following is an example of a noise absorption circuit with capacitor C and resistor R connected to an SSR.

The value of R and C must be decided carefully. The value of R must not be too large or the supply voltage (E) will not be able to satisfy the required input voltage value. The larger the value of C is, the longer the release time will be, due to the time required for C to discharge electricity.

Note:For low-voltage models, sufficient voltage may not be applied to the SSR because of the relationship between C, R, and the internal impedance. When deciding on a value for R, check the input impedance for the SSR.

2. Inductive Noise
Do not wire power lines alongside the input lines. Inductive noise may cause the SSR to malfunction. If inductive noise is imposed on the input terminals of the SSR, use the following cables according to the type of inductive noise, and reduce the noise level to less than the reset voltage of the SSR.

Twisted-pair wires:

Shielded cable:

A filter consisting of a combination of capacitor and resistor will effectively reduce noise generated from high-frequency equipment.

Note: R: 20 to 100 Ω
C: 0.01 to 1 μF

Input Conditions

1. Input Voltage Ripples
When there is a ripple in the input voltage, set so that the peak voltage is lower than the maximum operating voltage and the root voltage is above the minimum operating voltage.

2. Countermeasures for Leakage Current
When the SSR is powered by transistor output, the reset voltage may be insufficient due to leakage current of transistor during power OFF. To counteract this, connect bleeder resistance R as shown in the diagram below and set the resistance so that the voltage applied to both ends of the resistance is less than half of the reset voltage of the SSR.

The bleeder resistance R can be obtained in the way shown below.

E:

I_L:

I:

The actual value of the reset current is not given in the datasheet and so when calculating the value of the bleeder resistance, use the following formula.

For SSRs with constant-current input circuits (e.g., G3NA, G3PA, G3PB), calculation is performed at 0.1 mA.
The calculation for the G3M-202P DC24 is shown below as an example.

3. ON/OFF Frequency
An SSR has delay times called the operating time and reset time. Loads, such as inductive loads, also have delay times called the operating time and reset time. These delays must all be considered when determining the switching frequency.

4. Input Impedance
In SSRs which have wide input voltages (such as G3F and G3H), 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 the actual device before usage. See the following examples.

Applicable Input Impedance for a Photocoupler-type SSR without Indicators (Example)
G3F, G3H (Without Indicators)

Applicable Input Impedance for a Photocoupler-type SSR with Indicators (Example)
G3B, G3F, G3H (With Indicators)

Applicable Input Impedance (Example)
G3CN

Output Circuit

AC ON/OFF SSR Output Noise Surges

If there is a large voltage surge in the AC power supply where SSRs are used, the CR 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.
Varistors should generally be added because measuring surges is often difficult (except when it has been confirmed that there is no surge immediately before use).

Built-in surge absorption elements are included only with the G3NA, G3S, G3PA, G3PB, G3PC, G3NE, G3J, G3NH, G9H, G3DZ, G3RZ, and G3FM. When switching an inductive load ON and OFF, be sure to take countermeasures against surge, such as adding a surge absorbing element.

The following is an example of measures in which a surge voltage absorption element has been added.
OMRON confirmed the amount of resistance for the SSR output at the following impulse withstand voltage test conditions.

Conditions:

Select an element which meets the conditions in the table below 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 ON/OFF SSR Output Noise Surges

When an L load, such as a solenoid or electromagnetic valve is connected, connect 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 (V_z) of the Zener diode is increased.

Table 1. Absorption Element Example

Absorption element
	Diode	Diode + Zener diode	Varistor	CR
Effectiveness	○	○	Δ	×

(Reference)

1. Selecting a Diode
Withstand voltage = VRM ≥ Power supply voltage × 2
Forward current = IF ≥ Load current

2. Selecting a Zener Diode
Zener voltage = Vz < (SSR's connector − emitter voltage)* −
(Power supply voltage + 2 V)
Zener surge reverse power = PRSM > Vz × Load current × Safety
factor (2 to 3)

Note:When the Zener voltage is increased (Vz), the Zener diode capacity (PRSM) is also increased.

AND Circuits with DC Output SSRs

Use the G3DZ or G3RZ for the following type of circuit. Do not use standard SSRs, otherwise the circuit may not be reset

Self-holding Circuits

Self-holding circuits must use mechanical relays. SSRs cannot be used to design self-holding circuits.

Selecting an SSR with Differing Loads

The following provides examples of the inrush currents for different loads.

AC Load and Inrush Current

Load	Solenoid	Incandescent lamp	Motor	Relay	Capacitor	Resistance 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

1. Heater Load (Resistive Load)
Load without an inrush current. Generally used together with a voltage-output temperature controller for heater ON/OFF switching. When used with an SSR with zero cross function, suppresses most noise generated. 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 (G3PX) with a long soft-start time, or a constant-current type SSR.

2. Lamp Load
Large inrush current flows through incandescent lamps, halogen lamps, and so on (approx. 10 to 15 times higher than the rated current value). Select an SSR so that the peak value of inrush current does not exceed half the withstand surge current 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 withstand surge current 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.
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 withstand surge current when selecting an SSR. The SSR may be damaged by counterelectromotive force from the motor when the SSR is turned OFF.Be sure to install overvoltage protection.

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 the secondary circuit, the energizing current will reach the maximum value. Select an SSR so that the energizing current does not exceed half the withstand surge current of the SSR.

5. Half-wave Rectified Circuit
AC electromagnetic counters and 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.

(a) Connect a bleeder resistance with approximately 20% of the SSR load current.

(b)Use SSRs without the zero cross function.
This restriction does not apply, however, for switching of halfwave rectified break coils. Ask your OMRON representative for details.

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 diagram below.

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 reset.
Connect the bleeder resistance R in parallel to increase the SSR switching current.

8. Inverter Load
Do not use an inverter-controlled power supply as the load power supply for the SSR. Inverter-controlled waveforms are rectangular. The extremely large dV/dt may cause the SSR to misfire and prevent it from resetting.
An inverter-controlled power supply may be used on the input side provided the effective voltage is within the normal operating voltage range of the SSR.

9. Capacitive Load
The supply voltage plus the charge voltage of the capacitor is applied to both ends of the SSR when it is OFF. Therefore, use an SSR model with an input voltage rating twice the size of the supply voltage.
Limit the charge current of the capacitor to less than half the withstand surge current of the SSR.

Load Power Supply

1. Rectified Currents

If a DC load power supply is used for full-wave or half-wave rectified AC currents, be sure that the peak load current does not exceed the maximum usage load power supply of the SSR. Otherwise, overvoltage will cause damage to the output element of the SSR.

2. Operating Frequency for AC Load Power Supply

The operating frequency range for AC load power supply is 47 to 63 Hz.

3. Low AC Voltage Loads

If the load power supply is used under voltage below the minimum operating load voltage of the SSR, the loss time of the voltage applied to the load will become longer than that of the SSR operating voltage range. See the following load example. (The loss time is A < B.)
Make sure that this loss time will not cause problems, before operating the SSR.
If the load voltage falls below the trigger voltage, the SSR will not turn ON, so be sure to set the load voltage to 75 VAC min. (24 VAC for G3PA-VD and G3NA-2[][]B.)

An inductance (L) load causes a current phase delay as shown above. Therefore, the loss is not as great as that caused by a resistive (R) load.
This is because a high voltage is already imposed on the SSR when the input current to the SSR drops to zero and the SSR is turned OFF.

4. Phase-controlled AC Power Supplies

Phase-controlled power supply cannot be used.

Operation and Storage Environment Precautions

1. Ambient Operating Temperature

The rated value for the ambient operating temperature of the SSR is for when there is no heat build-up. For this reason, under conditions where heat dissipation is not good due to poor ventilation, and where heat may build up easily, the actual temperature of the SSR may exceed the rated value resulting in malfunction or urning.

When using the SSR, design the system to allow heat dissipation sufficient to stay below the Load Current vs. Ambient Temperature characteristic curve. Note also that the ambient temperature of the SSR may increase as a result of environmental conditions (e.g., climate or air-conditioning) and operating conditions (e.g., ounting in an airtight panel).

2. Operation and Storage Locations

Do not use or store the SSR in the following locations. Doing so may result in damage, malfunction, or deterioration of performance characteristics.

Locations subject to direct sunlight

Usage in locations subject to ambient temperatures outside the range specified for individual products

Usage in locations subject to relative humidity outside the range specified for individual products or locations subject to condensation as the result of severe changes in temperature

Storage in locations subject to ambient temperatures outside the range specified for individual products

Locations subject to corrosive or flammable gases

Locations subject to dust (especially iron dust) or salts

Locations subject to shock or vibration

Locations subject to exposure to water, oil, or chemicals

3. Extended Storage of the SSR

If the SSR is stored for an extended period of time, the terminal will be exposed to the air, reducing its solderability due to such effects as oxidation. Therefore, when installing a Relay onto a board after a long time in storage, check the state of the solder before use.

4. Vibration and Shock

Do not subject the SSR to excessive vibration or shock. Otherwise the SSR may malfunction or failure to operate may result due to deformation or damage to parts inside the SSR.

To prevent the SSR from abnormal vibration, do not install the Unit in locations or by means that will subject it to the vibrations from other devices, such as motors.

5. Solvents

Do not allow the SSR to come in contact with solvents, such as thinners or gasoline. Doing so will dissolve the markings on the SSR

6. Oil

Do not allow the SSR terminal cover to come in contact with oil.
Doing so will cause the cover to crack and become cloudy.

Working with SSRs

1. Leakage Current

A leakage current flows through a snubber circuit in the SSR even when there is no power input. Therefore, always turn OFF the power to the input or load and check that it is safe before replacing or wiring the SSR.

2. Screw Tightening Torque

Tighten the SSR terminal screws properly. If the screws are not tight, the SSR will be damaged by heat generated when the power is ON.
Perform wiring using the tightening torque shown in the following table.

SSR Terminal Screw Tightening Torque

Note:Excessive tightening may damage the screws. Tighten screws to within the above ranges.

3. SSR Mounting Panel Quality

If the G3NA, G3NE, or G3PB models with separate heat sinks are to be mounted directly onto the control panel, without the use of a heat sink, be sure to use a panel material with low thermal resistance, such as aluminum. Be sure to apply silicon grease for heat dissipation (e.g., the YG6260 from Toshiba or the G746 from Shin-Etsu) to the mounting surface.
Do not mount the SSR on a panel with high thermal resistance such as a panel coated with paint. Doing so will decrease the radiation efficiency of the SSR, causing heat damage to the SSR output element. Do not mount the SSR on a panel made of wood or any other flammable material. Otherwise the heat generated by the SSR will cause the wood to carbonize, and may cause a fire.

4. Surface-mounting Socket

1. Make sure that the surface-mounting socket screws are tightened securely when mounted. If the Unit is subjected to shock or vibration and the socket mounting screws are loose, the Socket and the SSR, or the lead wires may detach. The surfacemounting Sockets can be snapped on to the 35-mm DIN Track.

2.Use a holding bracket to ensure proper connection between the SSR and Socket. Otherwise the SSR may detach from the socket if an excessive vibration or shock is applied.

5. SSR Mounting and Dismounting Direction

Mount or dismount the SSR from the Socket perpendicular to the Socket surface. If it is mounted or dismounted with an inclination from the diagonal line, terminals of the SSR may bend and the SSR may not be properly inserted in the Socket.

6. Wiring for Wrapping Terminal Socket

Refer to the following table and conduct wiring properly. Improper wiring may cause the lead wires to detach.

Note:The PY[]QN uses a 0.65-mm-dia. wire that can be turned six times.
The PT[]QN uses a 0.8-mm-dia. wire that can be turned four times.

7. Tab Terminal Soldering Precautions

Do not solder the lead wires to the tab terminal. Otherwise the SSR (e.g., G3NE) components will be damaged.

8. Cutting Terminals

Do not cut the terminal using an auto-cutter. Cutting the terminal with devices such as an auto-cutter may damage the internal components.

9. Deformed Terminals

Do not attempt to repair or use a terminal that has been deformed. Otherwise excessive force will be applied to the SSR, and it will lose its original performance capabilities.

10. Hold-down Clips

Exercise care when pulling or inserting the hold-down clips so that their form is not distorted. Do not use a clip that has already been deformed. Otherwise excessive force will be applied to the SSR, causing it not to perform to its full capacity, and also it will not have enough holding power, causing the SSR to be loose, and resulting in damage to the contacts.

11. PCB SSR Soldering

SSRs must be soldered at 260°C within five seconds. For models, however, that conform to separate conditions, perform soldering according to the specified requirements.

Use a rosin-based non-corrosive flux that is compatible with the material of the SSR.

12. Ultrasonic Cleaning

Do not use ultrasonic cleaning. If the SSR is cleaned using ultrasonic cleaning after it has been mounted to the PCB, resonance due to ultrasonic waves may result in damage to the SSR's internal components.