How To Select A Suitable Heat Sink For Solid State Relays And Solid State Modules?

By Author: huimultd
Total Articles: 8
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§1. How the Heat Sink works
The role of the heat sink is to dissipate the heat generated by the solid state relay or module to ensure that the solid state relay or module will work stably and reliable at optimum conditions and not be burned and damaged due to high temperatures. The heat dissipation effect of the heat sink is not only related to its specification (size, shape), but also related to external environmental factors, such as the ambient temperature (season), ventilation conditions (natural cooling or forced cooling, and ventilation volume), and installation density. In addition, it is also necessary to consider whether the volume of the solid state relay or the module itself and the installation space of the heat sink in the equipment matches the specifications of the heat sink.

Factors affecting the heat sink performance
The cooling method of the solid state relay/module can be divided into Air Cooling method and Water Cooling method. And the air cooling heat sink can be farther divided into the Heat Sink (natural cooling) and Air Cooled Radiator (forced cooling by fan). Normally, if the load ...
... current of the solid state relay/module reaches 10A, a heat sink must be equipped; if the load current is 40A or more, an air-cooled radiator or a water-cooled radiator must be installed. When the module is used for the load with load power greater than 15 KW, it is recommended to use a suitable heat sink, and apply thermal grease between the heat sink and the SCR backplane, as well as cold air to cool down. If the current is below 350A, the module is cooled by forced air cooling; if the current is more than 400A, the cooling method for the module can be either air-cooling or water-cooling.

Heat dissipation reference standard: The temperature of the bottom plate (the side in contact with the heat sink) of the solid state relay or module does not exceed 80 °C.

Descriptions of the Heat Sink
In practical applications, we recommend installing a 75°C temperature switch (with a pair of normally closed contacts) on the mounting surface of the heat sink where near the edge area of the solid state relay or module (within 20mm), and then connecting the control signals of the solid state relay or module in series with the normally closed contacts. In this way, when the temperature of the detection point exceeds 75 °C, the normally closed contact will trip and cut off the control signal, and the output terminal of the solid state relay or module will be forcibly turned off to get protection. Generally, if the solid state relay or module is installed to the place with the actual current of each phase exceeding 50A, the high installation density and ambient temperature, it is better to apply a temperature switch for protection to ensure that the temperature of the bottom plate of the solid state relay or module does not exceed 80 ° C under severe conditions.

§2. How to calculate the Heat
At first, we should know that there is no one-to-one correspondence between the model (type) of the heat sink and the model (type) of the solid state relay or module. Since solid-state relays use transistors as electronic switching components/power components, the heat generated by the solid state relay or module is mainly related to the actual current of the load it drives, instead of its own rated current specification (current grade).

There is no relationship between solid state relay / solid state module and heat sink size, but the heat sink size is decided by the actual load current.
The heat generated by the solid state relay/module in practical applications can be calculated by the following formula:
1. Heat = Actual Load Current (Amps) * 1.5 W/Amps

Single phase ssr heat sink calculation, single phase voltage regulator module heat sink calculation
Note: The above formula is suitable for single phase solid state relays, single phase AC voltage regulator modules, and R series solid state voltage regulators. For three phase solid state relays and three phase AC voltage regulator modules, the actual load current should be the sum of the actual load currents.

2. Heat = Actual Load Current (Amps) * 3.0 W/Amps

Single phase fully-controlled bridge rectifier module heat sink calculation
Note: The above formula is suitable for single phase fully-controlled bridge rectifier module.

§3. How to select Heat Sink / Radiator
Applications of the heat sink / radiator
MGR (HUIMULTD) Heat Sink / Radiator series
The heat sinks/ radiators produced by our company are divided into two categories, for solid state relay and for module.

◆ For Solid State Relay: MG-I, MG-W, MG-T, MG-L, MG-H, MG-F, MG-Y.
These seven series are suitable for a variety of single phase solid state relays, single phase AC voltage regulator modules, R series solid state voltage regulators, industrial solid state relays and various three phase AC solid state relays, etc.

◆ For Module: E series, K series, Z series, Y series, G series.
These series are usually used with an air-cooled fan, suitable for DC commutator modules, voltage regulator modules, rectifier modules, phase-shift trigger modules, thyristor modules, hybrid modules, welding machine modules, etc.

The heat sinks/ radiators produced by our company are divided into two categories, for solid state relay and for module.◆ For Solid State Relay: MG-I, MG-W, MG-T, MG-L, MG-H, MG-F, MG-Y. These seven series are suitable for a variety of single phase solid state relays, single phase AC voltage regulator modules, R series solid state voltage regulators, industrial solid state relays and various three phase AC solid state relays, etc.◆ For Module: E series, K series, Z series, Y series, G series. These series are usually used with an air-cooled fan, suitable for DC commutator modules, voltage regulator modules, rectifier modules, phase-shift trigger modules, thyristor modules, hybrid modules, welding machine modules, etc.
The following are the general applications and selection of some radiators:

FULL ISOLATION SINGLE PHASE AC VOLTAGE REGULATOR MODULE (DTY)
The heat of the whole module = Actual load current (Amps) * 1.5 W/Amps. Customers can select MG-L, MG-H series heat sink according to actual needs.

FULL ISOLATION SINGLE PHASE FULLY-CONTROLLED BRIDGE RECTIFIER MODULE (DQZ)
The heat of the whole module = Actual load current (Amps) * 3.0 W/Amps. Customers can select MG-L, MG-H series heat sink according to actual needs.

FULL ISOLATION THREE PHASE AC VOLTAGE REGULATOR MODULE (MGR-ST)
The heat of the whole module = Actual load current (Amps) * 1.5 W/Amps. Customers can select MG-Y, MG-H series heat sink according to actual needs.

SOLID STATE RELAY THREE PHASE PHASE-SHIFT TRIGGER MODULE (SSR-3JK)
SSR-3JK and TB-3 generate very little heat and do not need to be mounted on a heat sink.

The SSR-3JK (with TB-3) matches the random solid state relays produced by our company. Users can build the SSR-3JK system by purchasing the SSR-3JK, the TB-3, three random conduction type SSRs and one heat sink to. If three long strip solid state relays are selected, they can be mounted on a Y series module air-cooled radiator with a fan installed to form a power unit; and if three rectangular solid state relays are selected, they can be mounted on the MG-Y heat sink to form a power unit.

THREE PHASE PHASE-SHIFT TRIGGER MODULE (SX-JK)
SX-JKA, SX-JKT, SX-JKZ, SX-JKB, TB-3A, and TB-3Z generate very little heat and do not need to be mounted on a heat sink.