Product Description:
High-power NTC thermistor MF73 series
R25(Ω): 0.2~20 Imax(A): 80A
[Product features] Reliable structure, easy installation, strong
surge current suppression capability, large energy absorption
[Product use] Various high-power switching power supplies, UPS
power supplies, conversion power supplies
1.Features:
●Reliable structure, easy to install.
● Strong surge current suppression capability, large energy
absorption.
● Large steady-state current.
● Long life and high reliability.
2.Dimension Of The Ultra Big Power NTC Thermistor MF73
| Body size | Φ40 | Φ45 | Φ50 |
| (Dmax)Diameter | 45 | 50 | 55 |
| (Tmax)/Thickness | 18 | 18 | 18 |
| (F±1.5)/Pitch | 22.5 | 22.5 | 22.5 |
| (L±2)/Lead length | 20 | 20 | 20 |
| (W±0.2)/Lead width | 8 | 8 | 8 |
| Lead thickness(H±0.1) | 1.0 | 1.0 | 1.0 |
| Body size | Φ40 | Φ45 | Φ50 |
| (Dmax)/Diameter | 45 | 50 | 55 |
| (Tmax)/Thickness | 18 | 18 | 18 |
| (F±1.5)/Pitch | 22.5 | 22.5 | 22.5 |
| (L±2)/Lead length | 30 | 30 | 30 |
| (W±0.2)/Lead width | 10 | 10 | 10 |
| Lead thickness(H±0.1) | 1.0 | 1.0 | 1.0 |
| Width of lower lead (W1±0.2) | 6 | 6 | 6 |
3.Specification Of The Ultra Big Power NTC Thermistor MF73 Body
diameter Φ40mm
| P/N | R25±20%(Ω) | Thermal sensitive index B±10%(K) | Max steady state current Imax(A) | Approx R of Max current Rmax(Ω) | Max power dissipation Pmax(W) | Thermal time constant (mW/C) | Thermal time constant (s) | Max impulse capacitance (uF)240VAC |
| MF73-0.2/50 | 0.2 | 2600 | 50 | 0.007 | 25 | ≥55 | ≤350 | 8000 |
| MF73-0.5/40 | 0.5 | 2600 | 40 | 0.008 | 6800 |
| MF73-3/28 | 3 | 2800 | 28 | 0.02 | 6800 |
| MF73-5/25 | 5 | 3000 | 25 | 0.028 | 4700 |
| MF73-8/20 | 8 | 3200 | 20 | 0.034 | 3300 |
| MF73-10/19 | 10 | 3200 | 19 | 0.038 | 3300 |
4.Body diameter Φ45mm
| P/N | R25±20%(Ω) | Thermal sensitive index B±10%(K) | Max steady state current Imax(A) | Approx R of Max current Rmax(Ω) | Max power dissipation Pmax(W) | Thermal time constant (mW/C) | Thermal time constant (s) | Max impulse capacitance (uF)240VAC |
| MF73-0.2/65 | 0.2 | 2600 | 65 | 0.006 | 30 | ≥70 | ≤480 | 11500 |
| MF73-0.5/50 | 0.5 | 2600 | 50 | 0.007 | 8000 |
| MF73-2/40 | 2 | 2600 | 40 | 0.012 | 8000 |
| MF73-5/30 | 5 | 3000 | 30 | 0.025 | 6800 |
| MF73-10/24 | 10 | 3200 | 24 | 0.032 | 4700 |
Body diameter Φ50mm
| P/N | R25±20%(Ω) | Thermal sensitive index B±10%(K) | Max steady state current Imax(A) | Approx R of Max current Rmax(Ω) | Max power dissipation Pmax(W) | Thermal time constant (mW/C) | Thermal time constant (s) | Max impulse capacitance (uF)240VAC |
| MF73-0.2/80 | 0.2 | 2600 | 80 | 0.004 | 36 | ≥90 | ≤650 | 15000 |
| MF73-0.5/60 | 0.5 | 2600 | 60 | 0.006 | 11500 |
| MF73-1/56 | 1 | 2600 | 56 | 0.008 | 11500 |
| MF73-3/40 | 3 | 2800 | 40 | 0.015 | 11500 |
| MF73-5/35 | 5 | 3000 | 35 | 0.022 | 8000 |
| MF73-6.8/32 | 6.8 | 3000 | 32 | 0.025 | 8000 |
| MF73-10/27 | 10 | 3200 | 27 | 0.03 | 6800 |
5.Application Scope
Various high-power switching power supplies, UPS power supplies,
conversion power supplies.
Electric vehicle chargers, charging piles.
Motor drive devices, high-power servo motor drivers, logic
controllers.
High-power plasma welding machines, cutting machines, high-power
lighting fixtures.
Nuclear magnetic resonance equipment, high-power audio amplifiers,
high-power toroidal transformers.
Solar panel arrays for large-capacity power inverters.
Industrial robots driven by high-voltage power supplies,
low-voltage intelligent electrical cabinets.
Principle of power NTC thermistor!
NTC (Negative Temperature Coefficient) thermistors are thermistors
with negative temperature coefficients and their resistance
decreases exponentially as the temperature rises. They are made of
metal oxides such as manganese (Mn), cobalt (Co), nickel (Ni), iron
(Fe), copper (Cu) and aluminum (Al) using ceramic technology.
When switching power supplies, motors, transformers and heaters are
powered on, instantaneous surge currents will be generated. The
greater the power of such equipment, the higher the surge current.
Large surge currents can cause circuit breaker damage, energy
receiver fuses, protection device failures and equipment
malfunctions.
Connecting one or more power-type NTC thermistors in series in the
power supply circuit is the most effective, economical and simplest
measure to suppress startup surge currents and protect electronic
components from damage or failure.
The thermal delay effect caused by the resistance value and thermal
inertia of the power type NTC thermistor body at room temperature
can effectively suppress the peak surge current (which can reach
tens or even hundreds of times the normal working current) in the
power supply circuit (especially the high-voltage large-capacitance
filter circuit) when the power is turned on. After the surge
current is suppressed, the self-heating effect under the continuous
action of the current (including the surge current and the normal
working current of the circuit) passing through it causes the
temperature of the resistor body to rise. The resistance value of
the power type NTC thermistor will drop to a very small level, the
voltage drop generated is low, and the power consumed is very
small, which will not affect the normal working current.
The figure below shows the waveform of the surge current when there
is a surge current suppression circuit with or without a power type
NTC thermistor.
The principle of the power type NTC thermistor!
Since power NTC thermistors are used as surge current suppression
devices, they have the advantages of significant effects, simple
circuits, low power consumption, high reliability, and low cost,
and are therefore widely used in conversion power supplies,
switching power supplies, UPS power supplies, transformers, motors,
smart electric cabinets, electric heaters, electronic energy-saving
lamps, electronic ballasts, displays, incandescent lamps, and other
lighting fixtures.
Principle of power NTC thermistors!
With the development of electronic technology, the requirements for
power NTC thermistors that suppress surge currents are small size,
high power, low power consumption, and high reliability. The
development direction of power NTC thermistors is: 1. Under the
same resistance value, steady-state current, and surge impact
conditions, the volume is smaller; 2. Under the same resistance
value and volume, the steady-state current is larger, and it has a
stronger ability to withstand current impact. 3. Smaller residual
resistance.
The power NTC thermistor series products have all passed UL, CUL,
TUV, and CQC safety certifications. The minimum zero-power
resistance can be below 1Ω, the steady-state current can reach 80A,
and the maximum chip diameter is 50mm.
