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CHAPTER 1 Introduction
1. Concept
Solid state relay (ab. SSR) is a mechanically passive version of its older counterpart the EMR (electromechanical relay), providing essentially the same performance, but without moving parts. It is a totally electronic device that depends on the electrical, magnetic, and optical properties of semiconductors and electrical components to accomplish its isolation and relay-switching functions.
2. Features
● High-speed, high-frequency switching operations.
● No contact failures.
● No clicking sounds.
● No contact bounce.
● No arc noise.
● Long life (reliability)>109 operations.
CHAPTER 2 How to choose and use the SSR?
1. Notes:
● Correct conducting wires, don’t mistake the input and output circuits.
● Testing the load resistance in order to avoid the short circuit before the power supply turn on.
● Do not obstruct the air flow to the SSR.
● Fastening the wires, otherwise, heat generated from the terminal may cause the SSR damage.
● Be sure to conduct wiring with the power supply turned OFF.
● Do not apply excessive voltage or current to the SSR input or output circuits.
2. Correct Choosing
It's important to choose the suitable SSR, The different loads bring surge current or overvoltage when the power turns on, so margin design, suggested the SSR block voltage is 2 to 3 times higher than the Load voltage. Refer to following chart for current value.
Please refer to SSR specification before using them.
Table 1:The Inrush current that different load switches
3. Correct Usage
3.1 Input Circuit
3.1.1 SSR shall be energized with adequate power (voltage or current). See figure 1 following.
3.1.2 Input noise may result in malfunction, Do not wire power lines alongside with the input lines.
3.1.3 For DC input, be careful about the correct polarity wires.
Notes : For SSR input such as resistive and constant current circuit , using it without current-limiting resister excessly .
3.2 Output Circuit
3.2.1 AC load
Switching the AC inductive load may bring over voltage, parallel connection betweenMOV (metal oxygen varistor) and the SSR output terminals is recommended.
Table 2:Suggesting the MOV type
3.2.2 DC load
Switching load such as the coil load may bring over voltage, parallel connection between the diode and the load terminals is recommended.
Table 3:
3.3 Environment
Do not operate or store the Relay in locations subject to direct sunlight or ultraviolet rays, otherwise the resin will be deteriorated which consequenetly leads to cracks and other damages to the case. Do not operate or store the relay in locations subject to exposure to water or chemicals; otherwise rust, corrosion ,and deterioration of the resin will occur.
Do not obstruct the air flow to the SSR, Please thermal design, refer to the curve of “Max. Load Current vs. Ambient Temperature”
3.4 Heat Sink Choosing
3.5 Mounting
3.5.1 PCB SSR
PCB SSR must be soldered at 260℃ within ten seconds. However, models which conform to separate conditions shall be soldered according to the specified requirements.
Table 4:Pan size list
3.5.2 Panel-mounting SSR
Table 5:Reference the torque
CHAPTER 3 Annex
1. SSR Classifications
SSRs can be classified by appearance, such as panel-mounting models, socket models, or PCB models, or by applications. The optimum SSR can be selected depending on the purpose, and this is another important feature of SSRs.
2. SSR Glossary
2.1 Zero Cross Circuit
A circuit which starts operation with the AC load voltage at close to zero-phase.
2.2 Trigger Circuit
A circuit for controlling the triac or thyristor trigger signal, which turns the load current ON and OFF.
2.3 Input Isolated Input Circuit
If the external circuit is prone to generating noise, or if wires from external sources are prone to the influence of inductive noise, in order to prevent malfunctions due to noise, it is necessary to electrically isolate internal circuits and external circuits (output circuits). An isolated input circuit is a circuit that isolates inputs and outputs by using components that are not connected electrically but that can transmit signals, such as contact relays or photocouplers.
2.4 Photocoupler
A component that runs the electric signal into a light emitter (e.g., LED), changes it to a light signal, and thenreturns it to an electric signal using a photoelectric conversion element, such as a photo transistor. The space used for transferring the light signal is isolated thus providing good insulation and a high propagation speed.
2.5 Rated Voltage
The voltage that serves as the standard value of an input signal voltage
Must-operate voltage Minimum input voltage when the output status changes from OFF to ON.
2.6 Input Impedance
The impedance of the input circuit and the resistance of current-limiting resistors used. Impedance varies with the input signal voltage in case of the constant current input method.
2.7 Operating Voltage
The permissible voltage range within which the voltage of an input signal voltage may fluctuate.
2.8 Reset voltage
Maximum input voltage when the output status changes from ON to OFF.
2.9 Input current
The current value when the rated voltage is applied.
2.10 Load Voltage
This is the effective value for the power supply voltage that can be used for load switching or in the continuous-OFF state.
2.11 Load Current
The effective value of the maximum current that can continuously flow into the output terminals under specified cooling conditions (i.e., the size, materials, thickness of the heat sink, and an ambient temperature radiating condition).
2.12 Leakage Current
The effective value of the current that can flow into the output terminals when a specified load voltage is applied to the SSR with the output turned OFF.
2.13 On-state Voltage Drop
The effective value of the AC voltage that appears across the output terminals when the maximum load current flows through the SSR under specified cooling conditions (such as the size, material, and thickness of heat sink, ambient temperature radiation conditions, etc.).
2.14 Min. Load Current
The minimum load current at which the SSR can operate normally.
2.15 Snubber Circuit
A circuit consisting of a resistor R and capacitor C, which prevents faulty ignition from occurring in the SSR triac by suppressing a sudden rise in the voltage applied to the triac.
2.16 Transient Voltage
This is a rating for an output semiconductor that used in an SSR for AC loads. Collector-emitter voltage (VCEO), this is a rating for an output semiconductor that used in an SSR for DC loads.
2.17 Turn-on Time
A time lag between the moment a specified signal voltage is imposed to the input terminals and the output is turned ON.
2.18 Turn-off Time
A time lag between the moment the imposed signal input is turned OFF and the output is turned OFF.
2.19 Insulation Resistance
The resistance between the input and output terminals or I/O terminals and metal housing (heat sink) when DC voltage is imposed.
2.20 Dielectric Strength
The effective AC voltage that the SSR can withstand when it is applied between the input terminals and output terminals or I/O terminals and metal housing (heat sink) for more than 1 minute.
2.21 Operating Temperature And Humidity
The ranges of temperature and humidity in which the SSR can operate normally under specified cooling, input/output voltage, and current conditions.
2.22 Storage Temperature
The temperature range in which the SSR can be stored without voltage imposition.
CHAPTER 4 SSR Market- FAQ by Customers
1. Frequently Asked Questions - SSR
Q: Minimum Questions we must ask the customer
A: Type of load – the more details we can get of the load profile the easier it is to specify the relay
Control Voltage ( Input Voltage)
Turn on voltage - must operate, output will be in ON state, normally open
Surge Current Rating I2T – pulse current withstand capability 1/2 pulse
Ambient temperature, operating temp range
Mechanical considerations.
Q: Do you do an equivalent relay to.....?
A: Please consult the Hongfa cross reference guide.
The main competitors you will find in Europe are Crydom, Celduc and Carlo Gavazzi. In a small number of large accounts Omron.
Q: Do you use your own thyristors in the HF SSR ?
A: No. HF purchases its packaged Triacs and SCR’s (family name thyristors) from approved market sources to HF specifications. The major SSR manufacturers currently purchase their thyristors on the open market.
HF is a relay specialist not a semiconductor manufacturer.
Q: Most manufacturers now use DBC material with the relay construction. Do HF use this technology?
A: Yes. The use of Direct Bond Copper (DBC) constructionis is a tested method of thermal management within the power electronics market. This material is purchased from the market leader Curamik, Germany.
On Triac output relays it is not necessary to use DBC.
Q: I would like to use a lower cost triac output relay but I am concerned about the reliability. Why are they cheaper than back to back SCR output relays ?
A: The triac within the relay is more susceptible to transient voltages than an SCR because it responds to current flow in both directions. A transient voltage in a severe environment could cause a triac output device to turn on or “false trigger”. This parameter is referred to as dv/dt, and is the level the SSR can withstand before turning on.
A back to back SCR construction uses a separate SCR for each direction of current flow and is less susceptible to this effect. HF fits a snubber on triac output relays to address this point. However for more severe applications the SCR output construction is preferred.
Q: EMC is a major concern. Do HF relays meet the requirements of the LVD ( Low Voltage Directive) ? Are the relays marked CE ?
A: We are currently working to meet the LVD requirements, and are considering CE marking for some of our more advanced panel mount products.
Q: What type of transient protection do HF offer with your relays ?
A: We offer two types of transient overvoltage protection. This is important because by far the greatest number of SSR failures are caused by an overvoltage condition. The first is TVS ( transient voltage suppression) diodes. These are standard products available on the market and are fitted internally across the relay input. They do not absorb the transient but redirect it to earth. There success depends on the speed of the transient pulse. TVS Diodes (or Zener Diodes) are one direction only and should not be used with Inductive loads.
For higher level bidirectional voltage transients we would use an MOV (Metal Oxide Varistor). These may be fitted internally or externally to the relay. The choice of MOV is based upon the level of transient suppression required. The MOV absorbs the transient.
Q: Do you have a range of heatsinks for your relays ? Is it possible to purchase the relay and heatsink as an assembly?
A: We are currently working to improve our range of heatsinks direct from HF. However our distributors in Europe are able to source heatsinks and supply a relay assembly with heatsink, Cover and thermal pad.
Q: Some manufacturers offer a “microcontroller” based relay which incorporates soft start, phase control functionality. Do HF offer this option?
A: This is a relatively new concept introduced in the past two years. After evaluation HF has concluded that the cost of integrating the functionality and software with the necessary levels of reliability is far more expensive than purchasing an SSR,adding external functionality and using existing software. At this time HF has no plans to introduce a “microcontroller” based SSR.
However should a customer with significant volumes require such a solution we do have the design capability.
Q: I am concerned about Chinese manufacturing quality. We have had some bad experiences?
A: HF is the number one manufacturer of EMR relays in China. In our SSR manufacturing we use international products from market leading suppliers. Optocouplers from Toshiba, DBC from Curamik, SCR from International Rectifier for example. We then assemble them using the best practice production techniques developed from our EMR production.HF factories are fully approved to ISO9001,ISO/TS16949.
Environmental System approved to ISO14001
Health and Safety to OHSAS18001
2. Check list
Heaters - Predominantly Resistive Load
Motor loads – High Surge up to 1.6 secs surge
Motor reversing – High Surge on reversal
Discharge lamps (fluorescent) – 20 times normal current Surge (PFC*)
Transformer Control – Hi Surge can be 100 times nominal current
Inductive loads - Specialised contact technical department
Motor Control – Use Random turn on, or zero cross relays
Electromagnetic Loads – Inductive load. Use Random turn on with low leakage
PFC* - Power Factor Correction
Application
Type of load
Load current nominal
Load Voltage
Ambient temperature
Power factor for motor switching
Transient Voltages
Surge Current rating 12T
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