Single - phase Solid - state Relay and Power Regulator: Which is Better?

Single - phase Solid - state Relay and Power Regulator: Which is Better?

- Single - phase Solid - state Relay

- When the load is an AC motor: Select an SSR with a current rating greater than or equal to 6 - 7 times the rated current of the motor.

- For loads such as AC electromagnets, intermediate relay coils, inductive coils, etc.: Select an SSR with a current rating greater than or equal to 4 times the rated current of the load. For a transformer, it is required to be greater than or equal to 5 times the rated current of the primary side of the transformer. For special inductive and capacitive loads, according to practical experience, the current margin of the SSR should be further enlarged.

- For power compensation capacitor loads: Select an SSR with a current rating greater than 5 times the rated current of the load.

- 【Special Attention】: Since the over - current burnout speed of the thyristor inside the SSR and the fusing speed of the fast - acting fuse are in the same order of magnitude when the load is short - circuited, the fast - acting fuse cannot protect the SSR 100%. The principle of selecting the current rating of the fast - acting fuse is to be slightly larger than the maximum load current. And the current rating of the single- phase solid - state relay should be as large as possible, so that the fast - acting fuse can protect the SSR more reliably. For loads such as motors and power compensation capacitors, which have a large inrush current when turned on, an air switch is advisable for protection. Air switches are divided into two types: "slow" and "fast". The "slow" type is mainly used for loads with a large starting inrush current, such as motors and power capacitors. The "fast" type is mainly used for resistive and other inductive loads. The protection speed of the air switch is lower than that of the fast - acting fuse, so it cannot protect the SSR 100% when the load is short - circuited. - Selection of Solid - state Relay Current Rating and Over - current Protection Over - current (a particularly serious case is load short - circuit) is the main cause of permanent damage to the internal output thyristor of the SSR. Fast - acting fuses and air switches are one of the over - current protection measures. Fuses can also be used for small - capacity SSRs. Many loads will generate a large inrush current when turned on. Due to insufficient heat dissipation, the inrush current, like over - current, is also one of the main causes of damage to the internal output thyristor of the SSR. Therefore, it is extremely important to ensure a certain current margin when selecting a solid - state relay.

- For resistive loads: Select an SSR with a current rating greater than or equal to 2 times the rated current of the load.

- 【Special Attention】: When there is an isolation (step - down) main transformer between the 'three - phase bridge' and the three - phase power grid (380V), the customer must state the rated voltages of the primary and secondary sides of the main transformer. Otherwise, the following scheme cannot be used directly - a synchronous transformer module or a trigger module needs to be customized.

- RC Absorption Circuit and Off - state Leakage Current** The function of the RC absorption circuit is to absorb surge voltage and improve the static dV/dt index. However, the RC circuit inside the SSR brings off - state leakage current. Generally, the leakage current of a 2A - 6A SSR has basically no impact on a load with a power of more than 10W (such as a motor), and the leakage current of a 10A - above SSR has basically no impact on a load with a power of more than 50W. In addition, in practical applications of large inductive load occasions, an RC absorption circuit can be additionally connected in parallel at the two output ends of the SSR to protect the SSR. For some users with small - power loads (such as intermediate relay coils, contactor coils, electromagnetic suction micro - power motors, etc.), we can customize solid - state relays with a leakage current of less than 1mA. For solid - state relays used in power expansion occasions, there should be no RC circuit inside, because the charging and discharging of the RC circuit may cause misoperation. When the resistance measured by the resistance range of a multimeter between the AC two ends of the solid - state relay is close to zero, it indicates that the thyristor inside this solid - state relay has been damaged. In addition to this, to determine the quality of a solid - state relay, a load - carrying circuit must be used.

- Power Regulator Nowadays, power regulators generally trigger thyristors through digital circuits to achieve voltage regulation and power regulation. Voltage regulation adopts a phase - shift control method, and power regulation has two methods: fixed - cycle power regulation and variable - cycle power regulation. The following details the application fields of the power regulator.

- Wide Application Fields of Power Regulator

- Electric Furnace Industry: Annealing furnace, drying furnace, quenching furnace, sintering furnace, crucible furnace, tunnel furnace, melting furnace, box - type electric furnace, well - type electric furnace, melting electric furnace, rolling electric furnace, vacuum electric furnace, trolley electric furnace, quenching electric furnace, aging electric furnace, bell - type electric furnace, atmosphere electric furnace, oven, experimental electric furnace, heat treatment, resistance furnace, vacuum furnace, mesh - belt furnace, high - temperature furnace, kiln, electric furnace.

- Mechanical Equipment: Packaging machinery, injection - molding machinery, heat - shrinkable machinery, extrusion machinery, food machinery, tempering equipment, plastic processing, infrared heating.

- Glass Industry: Glass fiber, glass forming, glass melting, glass printing, float glass production line, annealing tank.

- Automotive Industry: Spraying and drying, thermo - forming.

- Energy - saving Lighting: Tunnel lighting, street - lamp lighting, photography lighting, stage lighting.

- Chemical Industry: Distillation and evaporation, pre - heating system, pipeline heating, petrochemical industry, temperature compensation.

- Other Industries: Salt - bath furnace, power - frequency induction furnace, quenching furnace temperature control, heat - treatment furnace temperature
control, diamond press heating, high - power magnetization/demagnetization equipment, aviation power supply voltage regulation, central air - conditioning
electric heater temperature control, textile machinery, crystal production, powder metallurgy machinery, color picture tube production equipment, metallurgical
machinery and equipment, petrochemical machinery, smooth lighting adjustment, constant - voltage, constant - current and constant - power control, etc.

- Other Industries: Salt - bath furnace, power - frequency induction furnace, quenching furnace temperature control, heat - treatment furnace temperature control, diamond press heating, high - power magnetization/demagnetization equipment, aviation power supply voltage regulation, central air - conditioning electric heater temperature control, textile machinery, crystal production, powder metallurgy machinery, color picture tube production equipment, metallurgical machinery and equipment, petrochemical machinery, smooth lighting adjustment, constant - voltage, constant - current and constant - power control, etc.