BRIEF SAFETY MANUAL

SAFETY FIRST!

There is nothing more important than protecting your own safety.

Please strictly observe the safe operation rules and operation instruction. If you can't keep yourself safe, stop operating and leave immediately. If you encounter an uncertain or unsolvable problem, please consult the relevant technical personnel in time, please do not take risks. Before using, testing, maintaining electrical devices, you need to know the following:

§1.What are the dangers of electricity?

Electricity makes our life more convenient, but at the same time it can also causes great damage to our vulnerable body because of its enormous energy. The electric damage to the human body can be divided into: Electric Shock (such as tingling, burning sensation, spasm, paralysis, coma, ventricular fibrillation or stoppage, difficulty breathing or breathing stop); Electric Injury (such as electric burn, skin metallization). When the electric current passes through the heart, it can cause heart dysfunction, destroying the original contraction and expansion rhythm, heart failure, and ending blood circulation, causing death due to hypoxia in the brain. When the electric current passes through the central nervous system (brain and spinal cord), it can cause breathing stop and paralysis. The thermal effect of the electric current can cause electrical burns. The chemical effect of the electric current can cause electrical burns and metallization of the skin. The electromagnetic effect of the electric current will also produce radiation. The above injury may can cause secondary damage.

According to the different reactions of the human body after contacting the current, the current can be divided into the following four levels:
1. Perceived Current: The minimum current value that can be felt by the human body but does not cause harmful physiological reactions, which is 1mA (AC, 50~60Hz) or 5mA (DC) for adults.
2. Reaction Current: The minimum current value that can cause muscles to contract unconsciously, which is 5mA (AC, 50~60Hz) or 25mA (DC) for adult.
3. Safe Current: The maximum current value that the human body can freely get rid of the power supply without pathological damage after an electric shock, which is 10 mA (AC, 50~60Hz) or 50mA (DC) for adults.
4. Fatal Current: The minimum current value that can cause ventricular fibrillation and is life-threatening, which is typically 50 mA (AC, 50~60Hz), 80mA (DC) for adults.

The electrical resistance of the human skin is 1000~3000Ω (normally), and 800~1000Ω (when the skin horny outer layer is destroyed), so safety voltage can be calculated according to Ohm's law (I=U/R). Since the skin resistance is affected by many factors (such as clothing, sweat, conductive dust in the air), choosing the safe voltage is more reasonable instead of the safe current. In a dry environment, the safety voltage is 24VAC (50~60Hz) or 120VDC; in a humid environment, the safety voltage is 12VAC (50~60Hz) or 40VDC.

§2. How to avoid the danger of electricity?

1. Electrical Insulation

The electrically charged object (or charged body) must be enclosed by a non-conductive insulating material. Keeping the insulation of distribution lines and electrical equipment is the most basic prerequisite to ensure personal safety and normal operation of electrical equipment. The performance of electrical insulation can be measured by its insulation resistance and dielectric strength.

2. Safety Distance

The electrically charged objects should be kept at a certain distance from the ground, the human body, other charged objects, and other facilities or equipment. Outside such safety distance, there is no danger when the human body or object is close to the charged body, such as the safety distance for the power distribution device, the maintenance safety distance, and the operation safety distance.

3. Safe Current Carrying Capacity

The safe current carrying capacity is the maximum amount of current that is allowed to continuously pass through the device. If the current exceeds the safe current carrying capacity of the device, the heat generated by the device will exceed its allowable value, which will cause damage to the insulation layer and even cause electric leakage and fire. Therefore, before selecting a device, you need to know its safe current carrying capacity.

4. Marking

The clear, accurate and uniform marking is another important prerequisite for ensuring the safety of electricity. For instance, the hazardous zone should be marked with a warning marking, the device with different structure and different parameters can be identified with the model number marking, the wires with different nature and different purposes can be identified by color marking (For example, Phase A wire is yellow, Phase B wire is green, Phase C wire is red, exposed grounding wire is black; AC loop of secondary system circuit is yellow, the negative power supply is blue, and the signal and warning circuits are white).

§3. How to operate safely

1. Protective Equipment

Before operating electrical device, please ensure that you have worn rubber-insulated gloves, insulated shoes, anti-static clothing, safety goggle and other protective equipment. And you also need to confirm that there are fire-fighting facilities or other safety facilities within the specified range.

2. Operating Tools

You need to check if the tool you are using has insulation ability, if the insulation material is aged and dropped, it should be replaced immediately. If there is a risk of explosion and fire, use an explosion-proof tool.

3. Operation Precautions

● Please do not operate with power.
● Please ensure that the working environment is dry, the temperature is suitable, and the ventilation conditions are good.
● Please make sure the working table is clean, and free of dust, metal debris, etc.
● Please make sure that wires are correctly connected according to the marking. For DC devices, please do not reverse the positive and negative poles.
● Please ensure that all electrical and electronic equipment is working within its rated value.
● Please make sure all the device is safely grounded.
● If there is a large capacitance or a large inductance in the device, you cannot directly touch it even after the power is turned off, because it will output a high voltage of several thousand volts in an instant. You should wait for its natural discharge or force discharge it using auxiliary equipment under safe conditions.
● Before using the voltage regulating device, make sure the regulator is in the initial state (zero voltage, 0V).
● When using electrical or electronic equipment, once you smell the burnt smell, hear abnormal sounds, see abnormal conditions such as flashing of the display or indicator light, please immediately turn off the power and check the equipment.
● If the device needs to be replaced due to a malfunction, it is recommended to use a device with the same model or technical parameters.
● Please do not press the stop button immediately after starting the electrical motor, because its starting current is 6-7 times the rated current, if it stops immediately, it will burn out other equipment.

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The above content was updated on Nov. 16, 2019.

Electrical Calculation

We make a list of some common calculation formulas that you might use when choosing a solid state relay (SSR)/solid state module (SSM) or designing a circuit.

Attention: HUIMU Industrial (HUIMULTD) assumes no liability for errors in data nor in safe and/or satisfactory operation of equipment designed from this information.

Electric Power Calculation Formulas

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● Single Phase Load

P=U·I·cosφ
U is the Voltage (usually 220VAC), I is the Current.

● Three Phase Load

P=√3·U_L·I_L·cosφ=3·U_P·I_P·cosφ
U_L is the Line Voltage (normally 380VAC), I_L is the Line Current, U_P is the Phase Voltage (normally 220VAC), I_P is the Phase Current.

● Power Factor (cos φ)

If the load type is resistive load (such as electric heater), then cos φ=1; If the load type is inductive load (such as an electric motor), then 0<cos φ<1. Take electric motor as a example, when the electric motor is fully loaded, the active current is the largest, the reactive current is the smallest, and the power factor is about 0.85; when the load is light or no load, the active current is small, the reactive current is large, and the power factor is between 0.4 and 0.7. Thus, we usually take a power factor of 0.78 or 0.8. If the load type is capacitive load (such as power compensator), then cos φ<0.

● Peak Value, Effective Value, Average Value

The AC voltage is a sine wave, and its voltage value changes periodically from 0 to the maximum value (U_MAX), so its peak value (U_PK) is equal to the maximum value. The AC effective value is specified by the thermal effect of the current, that is, let an AC current and a DC current pass through resistors with the same resistance value respectively, and if they generate equal heat in the same time, then the effective value of this AC current is equaled to the value of this DC current. Since the effective value of the sinusoidal AC voltage is equal to its root mean square value (U_RMS or U), U_RMS is generally used to represent the effective value of the AC voltage. Normally, the AC voltage value we detect through detection equipment (such as multimeters) is the effective voltage value, and the AC voltage value marked on the electrical equipment is also the effective value (such as 220VAC, 380VAC). The average AC voltage (U_AV) is the average voltage value over a period. The average AC voltage is equal to the integral of the voltage in one cycle divided by 2π (the time in one cycle). Theoretically, the DC voltage value obtained after full-wave rectification of the AC voltage is equal to the average value of the AC voltage.

U_PK=√2·U_RMS=1.414·U_RMS
U_AV=2/π·U_PK=0.637·U_PK

Similarly, according to Ohm's law, we can get the peak value (IPK or IMAX), the effective value (IRMS), and the average value (IAV) of the AC current.

I_PK=√2·I_RMS=1.414·I_RMS
I_AV=2/π·I_PK=0.637·I_PK

Because the value of DC current or DC voltage is constant, they have no maximum value, effective value, and average value.

Derating Factor Calculation Formulas

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Since the performance of the solid state relay/solid state module is affected by the working environment and the load type, the Derating Factor (or Current Multiple Factor) should be considered when selecting the rated current value of the solid state relay/solid state module.

I_R=I_L/α
I_R is the rated current value of the solid state relay/solid state module;
I_L is the DC load current value or the AC load current effective value (rms value);
α is the derating factor.

According to the working environment of the solid state relay/solid state module (ventilation, temperature, service time, etc.), the derating factor can be divided into three levels: Protected, Normal and Severe.
For resistive loads (such as electric heater, incandesc ent lamp, etc.), α = 0.5 (Protected), α = 0.5 (Normal), α = 0.3 (Severe);
For inductive loads (such as motor, transformer, etc.), α = 0.2 (Protected), α = 0.16 (Normal), α = 0.14 (Severe);
For capacitive loads (such as power compensator, etc.), α = 0.2 (Protected), α = 0.16 (Normal), α = 0.14 (Severe).

Current Multiple Factor is the inverse of Derating Factor.

I_R=I_L·β
I_R is the rated current value of the solid state relay/solid state module;
I_L is the DC load current value or the AC load current effective value (rms value);
β is the current multiple factor.

For resistive loads (such as electric heater, incandescent lamp, etc.), β = 2 (Protected), β = 2 (Normal), β = 3 (Severe);
For inductive loads (such as motor, transformer, etc.), β = 5 (Protected), β = 6 (Normal), β = 7 (Severe);
For capacitive loads (such as power compensator, etc.), β = 5 (Protected), β = 6 (Normal), β = 7 (Severe).

For example, if you need a DC to AC Panel solid state relay to switch a 220VAC, 10A resistive load, and require this solid state relay to work uninterrupted in a poor ventilation environment, then according the derating factor β = 3 (Severe), you should choose MGR-1D4830 (DC to AC, load: 480VAC, 30A).

Varistor Calculation Formulas

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If the load peak voltage is high, be sure to connect the varistor (such MOV, ZNR) in parallel to the output terminal of the solid state relay/ solid state module.

V_imA=V_1mA=(a·v)/(b·c)
V_imA is the varistor voltage when the current is XmA. Due to the current value is usually set at 1mA, it can also be expressed as V_1mA; a is the voltage fluctuation coefficient, generally 1.2; b is the varistor error value, generally 0.85; c is the aging coefficient of the component, generally 0.9; v is the DC operating voltage, or the AC rms voltage.

Therefore, the above formula can be simplified as:
For DC circuit，V_imA≈1.6·v
For AC circuit，V_imA≈1.6·V_p=1.6·√2·V_AC
V_p is the peak voltage, V_AC is the effective value.

Generally, the varistor voltage is 1.6 times the load voltage, but when the load is an inductive load, the varistor voltage should be 1.6-1.9 times the load voltage to ensure safety.

Rectifier Circuit Calculation Formulas

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● Single-Phase Half-Wave Rectification Circuit

U₀=0.45·U₂
I₀=0.45·U₂/R_L
I_V=I₀
U_RM=√2·U₂

● Single-Phase Full-Wave Rectification Circuit

U₀=0.9·U₂
I₀=0.9·U₂/R_L
I_V=1/2·I₀
U_RM=2·√2·U₂

● Single-Phase Bridge Rectification Circuit

U₀=0.9·U₂
I₀=0.9·U₂/R_L
I_V=1/2·I₀
U_RM=√2·U₂

● Single-Phase Half-Wave Rectification Filter Circuit

U₀=U₂
I₀=U₂/R_L
I_v=1/2·I₀
U_RM=2·√2·U₂
C≥(3~5)·T/R_L
T=1/f, if f=50Hz, then T=1/50=20ms

● Single-Phase Full-Wave Rectification Filter Circuit

U₀=1.2·U₂
I₀=1.2·U₂/R_L
I_v=1/2·I₀
U_RM=√2·U₂
C≥(3~5)·T/2R_L
T=1/f, if f=50Hz, then T=1/50=20ms

● Single-Phase Bridge Rectification Filter Circuit

U₀=1.2·U₂
I₀=1.2·U₂/R_L
I_v=1/2·I₀
U_RM=√2·U₂
C≥(3~5)·T/2R_L
T=1/f, if f=50Hz, then T=1/50=20ms

V_RSM=V_RRM+200V
V_RSM (Non-Repetitive Peak Reverse Voltage), is the maximum allowable surge value of reverse voltage that can be applied to the reverse direction of the device; V_RRM (Repetitive Peak Reverse Voltage), is the maximum allowable value of reverse voltage that can be repeatedly applied to the reverse direction of the device.

V_DSM =V_DRM +200V
V_DSM (Non-Repetitive Peak Off-State Voltage), is the maximum allowable surge value of off-state voltage that can be applied to the forward direction of the device; V_DRM (Repetitive Peak Off-State Voltage), is the maximum allowable value of off-state voltage that can be repeatedly applied to the forward direction of the device.

I_t²=I_TSM²·t_w/2
t_w is the half sine period; I_TSM it the maximum non-repetitive on-state surge current in one cycle; if the frequency is 50Hz, I_t²=0.005 I_TSM² (Amps²·sec)

Heat Generation Calculation Formulas

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When the solid state relays are working, the output circuit has a voltage drop of 1~2V. When the solid state modules (or power modules) are working, the output circuit has a voltage drop of 2~4V. And the electrical energy they consume is transmitted as heat, and this heat is only related to their operating current. The solid state relay has a calorific value of 1.5 watts per ampere (1.5 W/A) and the solid state module has a calorific value of 3.0 watts per ampere (3.0 W/A). The heat generated by the three-phase circuit is the sum of the heat generated by each phase.

Single Phase or DC solid state relay: P=1.5·I
Single Phase or DC solid state module: P=3.0·I
P is the heat generated by solid state relay/solid state module, and the unit is W; I is the actual load current, and the unit is A.

Normally, if the load current is 10A, a heat sink must be equipped. If the load current is 40A or higher, an air-cooled or water-cooled heat sink must be equipped.

Heat Dissipation Calculation Formulas

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The heat dissipation performance of the heat sink is related to its material, shape, temperature difference, and etc.

Q=h·A·η·ΔT
Q is the heat dissipated by the heat sink; h is the total thermal conductivity of the heat sink (W/cm²·°C), generally aluminum material is about 2.12W/cm²·°C, the copper material is about 3.85W/cm²·°C, and the steel material is about 0.46W/cm² °C; A is the surface area of the heat sink (cm²); η is the heat sink efficiency, which is mainly determined by the shape of the heat sink; ΔT is the difference between the maximum temperature of the heat sink and the ambient temperature (°C).

Therefore, it can be obtained from the above formula that the larger the surface area of the heat sink is, the larger the difference from the ambient temperature is, and the better the heat dissipation performance is.

Common Unit Conversion

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1MΩ=10³kΩ=10⁶Ω=10⁹mΩ
1F=10³mF=10⁶μF=10⁹nF=10¹²pF
1H=10³mH=10⁶μH
1MV=10³kV=10⁶V=10⁹mV=10¹²μH
1kA=10³A=10⁶mA=10⁹μA
1W=10³mW=1J/s=1V·A
1HP=0.75kW
1kW·h=10³W·h=10³V·A·h=10⁶ V·mA·h=3.6·10⁶J
1cm=10mm=0.39in
1cm²=0.16sq in
°F=1.8°C+32
K=°C+273.15

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The above content was updated on Nov. 29, 2019.
There may be errors and omissions during the content collation and upload process, so all things above are for reference only. If you find any problems, your correction will be grateful.

How To Order SSR

The PDF file below shows the full range of solid state relay series, module series and heat sink series produced by MGR, which can be viewed online or downloaded locally for convenient selection.