Connection Diagram of AC Control SSR

This is an Application note i used to give with my ssr – app011.pdf – Ananth

SSR or Solid State Relay or Electronic Relay

This is a Thyristor Based Normally Open 230V Switch that can be turned on / off at a fast rate. This switches at Zero Crossover .Built In Snubber reduces EMI and protects the SSR. USE SAME PHASE FOR I/P & O/P.

AC-AC SSR Wiring

  • No moving parts hence no wear and tear.
  • Dissipates Heat when in On Condition.
  • Use adequate Heat Sink or SSR will fail. ( 10g / Amp)
  • Dissipation is 1.5 Watts per Amp thru Load.
  • Input to Output is optically isolated 2kV.
  • This one is AC 230V Control AC 230V N.O. Output.
  • Off state snubber Leakage is around 5 mA.

Notes –

The Termination’s of High Current Lines going to Load must be very tight and crimped. Loose contacts will Spark and cause Fire.

Fuse Rating of HRC Fuse – High Rupture Capacity (HRC) Fuse is Safe and Reliable. 5kW Heater at 230V is 5,000 / 230 in Amps of Fuse Rating.

Connection Diagram of DC PCB SSR

This is an Application note i used to give with my ssr – app012.pdf – Ananth

Diagram of SSR 5000 DC 3-30 Control / 230V AC N.O. @ 3A.

This is a Thyristor Based Normally Open 230V Switch that can be turned on / off at a fast rate. This switches at Zero Crossover . Use 5V DC for Best Results.

PCB SSR Wiring

  • No moving parts hence no wear and tear.
  • Dissipates Heat when in On Condition 5 Watts @ 3 Amps.
  • Mount with adequate Air Ventilation for 3 Amps.
  • Dissipation is 1.4 Watts per Amp thru Load.
  • Input to Output is optically isolated 1kV.
  • This one is DC 3-30 Control AC 230V N.O. Output.
  • Off state snubber Leakage is around 1 mA.

Notes –

The Termination’s of High Current Lines going to Load must be very tight and crimped. Loose contacts will Spark and cause Fire.

Fast Blow Fuse is to be used. Use a 2 Amps Fuse with Holder in the Hot Line.

AC-AC-SSR Solid State Relay

This is a AC Control Input AC Output SSR Solid State Relay. When a Process Controller has an AC output or a system generates an AC signal of above 100V AC to signal the load to turn on, this device can be used. A BTA40-600 and MOC3041 are used in this.

A high voltage plastic cap limits current to a bridge which generates a small DC from 230 V AC, this drives MOC3041. The rest is the same. It is better to use a DC control SSR where possible. This AC control SSR is used where only an AC control signal is available. The BTA series has the heatsink tab insulated from the Triac chip inside. The BTB needs electrical insulation to the heatsink.

ac-ac-ssr

These devices BTA40600 and MOC3041 make SSR’s very simple. They have proved very reliable and rugged in the field, overrate your designs, use heat sinks and seal the SSR with thermally conductive epoxy. Alumina with ciba araldite without any other filler or dye is the best way to hermitically seal.

DC-DC SSR Solid State Relay

This is a DC Input DC Output SSR Solid State Relay. It was made for Printing or Photo Processing Equipment. It has an optical isolation and can be used for inductive loads.

DC SSR

The R1 Limits current and Z1 and D1 protects. The 2N3904 limits current in the Opto-Led. When the LED in CNY17-3 turns on, the Light passes thru a electrically insulating area and falls on the photo-transistor in the opto-coupler. This transistor conducts biasing Q2 PNP power transistor. Then Q2 drives Q3 to saturation, turning it on. Q3 is a High-Voltage and High-Power rugged device. This can derive a solenoid, DC motor or Lamp.

DC Load DC Control SSR

Normally Closed AC SSR

This is a Normally Closed PCB Mount SSR. That means when DC Control input is low, the triac is ON, the output passes the load current to turn on small heater-motor-lamp or a bigger contacter-drive etc.

NC Solid State Relay or SSR

When input DC is high the output is OFF. This is also Optically Isolated from Mains. A Microcontroller output which is buffered by some driver can drive this relay. It is better that in big systems these SSR Modules can be on another PCB, to avoid mains wiring near Logic circuits. But this cannot be used for medical electronics, or critical applications. More reliability and visual isolation of voltages may be required for such equipment.

NC AC Load SSR DC control

NO-NC SSR Plastic Box

This was a Fire Retardant Plastic Box which was made for the SSR I/O Stackable Modules. DC Control for an AC Load. Usually it is to control another Big Three phase contactor;

Pneumatic or Steam Valve, Solenoids-Motors. When Mounted at the end of the PCB it offers over 2kV Isolation from the Digital Circuits. The Output 230V signals NO-NC, can control Light Loads like the Coil of a Big 230V Relay also called contactor.

NO NC SSR Box

It could be Mounted on a PCB by soldering or a Plugin Base. It is better to have Crimped connections or Terminals. A very good quality spring Loaded Socket may also work but it has to be rated for many operations. Things like Nickle Alloy Plated, Beryllium Copper were the Materials Jargon. A contact resistance in the Terminals, a mismatch of alloys, electrochemical reactions, Corrosive Fumes, Brine or High Humidity can build a Loose connection into a Dangerous Sparking Contact.

Not only the Functionality of the SSR will be affected in a Sparking Contact, but a Risk of a Fire Developing. When Inflammable Materials or Volatile Liquids are Present Nearby, the risk is even greater.

Read More – Solid State Relays SSR

Three Phase Solid State Relay

This is R-Y-B three phase 40A 440V AC Solid State Relay with 3-30 V DC Control Signal. It has Built in HeatSink and Fan. It is good for Controlling a Bank of heaters. This model could go upto 120A with SSR’s in parallel for Proportional Control. Solid State Relays SSR.

This is a Contacter replacement, it will switch R-Y-B phases. It is a high power SSR. In some places it is unwise to use an SSR, a Electromechanical Contacter will perform better. The merit of SSR is fast switching, no wear and tear. No dust humidity influence.

Three Phase SSR