Inrush Current Blog Archive

Inrush Current Blog Archive

The inrush current blog archive contains articles relating to inrush current, it’s causes, cures, and prevention.

Inrush Current Limiting

PTC Thermistors vs. NTC Thermistors for Inrush Current

Prevent Inrush Current with PTC and NTC Thermistors PTC and NTC thermistors can provide inrush current protection in various equipment, machinery, and systems. Inrush current affects a wide range of products, from transformers to motors, and electronics from power supplies to inverters.  Inrush current becomes further complicated by systems that switch on and off quickly, such as welding equipment and HVAC systems. This post will give you a brief overview of … Continue Reading

Inverter Pre-Charge Circuit Inrush Current

Inverter Pre-Charge Circuit Inrush Current

Pre-Charge Circuits Prevent Damage to Inverters Severe damage can occur to inverters when the inrush current is too great for the inverter. Pre-charge circuits protect the inverters by controlling the initial power surge. PTC thermistors can help a pre-charge circuit protect the inverter.  Inrush current occurs when the maximum instantaneous input current flows through a system when the electrical power is switched on. In power tools, such as power drives,  … Continue Reading

DC Motor Inrush Current

How To Limit DC Motor Inrush Current

Choosing An Inrush Current Limiter To Preserve Your DC Motor So, what does an Inrush Current Limiter have to do with DC motor inrush? More than you may think. DC motor inrush is the maximum, instantaneous input current drawn by the DC motor when first turned on and it is important to know how to limit the inrush current to prevent possible damage to the motor. A DC motor converts … Continue Reading

The Effectiveness of Inrush Current Limiters for Vacuum Motors Experiencing High Inrush Current

Inrush current can cause considerable damage to electrical applications. It is important to control this starting current with the right inrush current limiter. In this article we look at what can happen when you choose the wrong circuit protection device. Then we demonstrate how to choose the right circuit protection device. Finally, we show the dramatic difference between using an inrush resistor and not using one in a vacuum motor. … Continue Reading

What is an Inrush Current Limiter? The Single Part Solution

There is a lot of information available about inrush current limiters and their different applications, capabilities, limitations, and other particular details. But very infrequently is the most basic question asked, what is an inrush current limiter and why is it used? To access, appreciate, and apply the benefits and solutions that these components provide, it is important to first be able to understand, acknowledge, and answer the question of what … Continue Reading

DC/DC Converter Inrush Current

Regulating Inrush Current at Powerup At powerup, DC/DC converters draw a large amount of electrical current.  This inrush current can be fatal to both the converter and the load if not controlled at the beginning. To achieve a soft start, when the electrical current rises gradually to its specified level, the use of an NTC Thermistor Inrush Current Limiter can be vital. DC/DC Converters DC/DC converters transform a source of … Continue Reading

Inrush Current Limiter Family

Cool-down Time for Inrush Current Limiters

NTC Thermistor Inrush Current Limiters are used to reduce the inrush current that occurs when an electrical device is switched on. High inrush current is the result of the maximum instantaneous input current drawn by electrical equipment during the initial power up. As technology continues to advance, most systems today run efficiently and maintain a low impedance, which in turn contributes to a high inrush current. Cool-Down Time After Power … Continue Reading

Inrush Current Limiter Replacement for Pool Chlorinators

The sky is blue. The outdoor temperature is rising. The time to get that pool back up and running is now! Whether you run a pool business or are a pool owner, you know how important it is to have your pool chlorinator running smoothly, all season long. But what do you do when your pool chlorinator stops working?  Buying a new one might be the first thing that comes … Continue Reading

Capacitor Inrush Current

Reducing Inrush Current to Capacitors Calculating the amount of current flowing to a capacitor, then protecting your load from this initial flow of current is important for any electronic device. The ability to reduce this inrush, caused at powerup, can typically be accomplished by the use of an NTC (negative temperature coefficient) thermistor inrush current limiter. Cause of the Inrush Current Filter capacitors are devices designed to reduce the effect … Continue Reading

Ametherm’s Sensing Thermistors and Inrush Current Limiter’s Part Numbers Decoded

Ametherm’s Temperature Sensor and Inrush Current Limiter Part Numbers Decoded

From the creation of the first inrush current limiter series, back in 1994, Ametherm knew that having logic behind the series naming convention would be important.  Not only for organizational means but also to easily identify the components of the inrush current limiters and NTC thermistor temperature sensors. Both product lines, the inrush current limiters and NTC thermistor temperature sensors, have stringent guidelines created to get the most accurate description … Continue Reading

Inrush Current Protection for LED Lighting Retrofits

Inrush current protection for LED lighting retrofits can be key to a successful lighting upgrade. Retrofit of LED lighting into an existing electrical system relies on the equipment already in place. This can be problematical due to the high inrush current created by the LED drivers. Falling LED prices and immediate energy savings are propelling the upgrade of older lighting modalities to new LED lighting for commercial and institutional users. For facilities management, benefits of a … Continue Reading

High Inrush Current Protection for Industrial Equipment

Large power users require mitigation of inrush currents as part of overall energy management strategy. Industrial automation with motor drives and logic controllers, high voltage power supplies feeding industrial robotics and solar panel arrays with large capacity power inverters all require inrush current limiting.   Overview   Inrush current is the momentary surge of current created when power is turned on to motors, transformers, power supplies and heating elements. These … Continue Reading

circuit board using UL certified SL12 10006

Overloaded Circuit Board? Clean House with our New UL Certified SL12 10006

We couldn’t keep it a secret any longer. Finally, a UL approved circuit protection thermistor (Inrush Current Limiter) that’s just 12.3mm in diameter but packs an energy rating of 40 (J), yes; we said 40 (J) plus a maximum continuous current rating of 6.0A. Meet our upgraded UL certified SL12 10006 for limiting inrush current. We think this device is a game changer! Up until now if an application required … Continue Reading

limiting heat lamp inrush current

Limiting Heat Lamp Inrush Current Protects Relay Contacts

Limiting Heat Lamp Inrush Current Incandescent heat lamps create a large inrush current when first powered on. Limiting heat lamp inrush current prevents relay damage and extends lamp life. Heat lamps can be used to warm enclosed areas such as livestock pens and chicken coops. Banks of incandescent heat lamps are mounted overhead. As the number of heat lamps increases, limiting heat lamp inrush current becomes more important. Over current can damage relay contacts in … Continue Reading

Protect your RV AC motor with Inrush Current Limiters

Limit AC Motor Inrush Current

Limit AC Motor Inrush Current In Air Conditioner Application AC motors used in air conditioning equipment draw large inrush current at power-on. A recent customer of ours had a 115VAC air conditioner installed in their travel trailer for park use. This 15,000-BTU unit required 16 amps for simultaneous compressor and blower motor operation. The trailer was also equipped with a load-shedding power distribution panel to protect its wiring harness from overload. If more … Continue Reading

Calculate Inrush Current in Three Steps

An Inrush Current Limiter (ICL) can protect electrical equipment from overheating when switched on because of inrush current. And, because inrush current equals the maximum instantaneous surge of incoming current from a power source, it can be as much as 2 to 3 times the steady state current of the attached device. Inrush Current Calculators are the best way to measure the resistance versus temperature curve to get the right Inrush Current Limiter. … Continue Reading

solor-panel for energy efficiency

Alternative Energy Applications for MS35 Inrush Current Limiters

Application Overview Ametherm’s MS35 series inrush current limiting thermistors play a key role in alternative energy applications by avoiding current spikes in the power generated by wind turbines, solar panels, and other sources as it’s fed into batteries, inverters, and other energy storage components. The MS35 devices are also used to regulate the release of battery energy in electric vehicles and in pre-charge circuits for many different types of battery … Continue Reading

Toroidal Transformer Inrush Current Issues Got You Down? We’ve Got the Answer

What You Need to Know About Toroidal Transformer Inrush Current Toroidal Transformer Inrush Current can cause some serious damage if not appropriately managed. Inrush current can cause circuit breakers to trip and fuses to blow. Additionally, it can cause a complete failure of the transformer itself. And if that weren’t enough to give you a headache, excessive inrush current can also limit the total number of devices which can be … Continue Reading

Design Guidelines for a Power Factor Correction (PFC) Circuit Using a Capacitor and an NTC Thermistor

OBJECTIVE Ametherm inrush current limiters are used in many applications today that require suppression of surge current when power is first applied to the system. One of the popular applications of Ametherm inrush current limiters is in power factor correction circuits. This article provides a solution for finding the correct power factor correction (PFC) circuit for an inductive load. This solution is suitable for applications that include ballasts, LED drivers, … Continue Reading

Enabling Higher Power Efficiency through Thermistor-based Temperature Compensation

By Balaji Santhanam, Hubble Power Systems Mehdi Samii, Ametherm Inc. Originally Published in Power System Design  Magazine  As electronic systems continue to become more compact, temperature plays an increasingly important role in system reliability and power efficiency. Many engineers are already familiar with how temperature can affect reliability; if a system becomes too hot, device operation can become unpredictable. Using a simple temperature sensor like a thermistor, the host processor can monitor … Continue Reading

Transformer Inrush Current: Limiting a 40VA Transformer

Have you ever turned on a transformer and heard a loud humming sound? What about having a blown fuse or tripped circuit breaker? These signs can all indicate transformer inrush current. Transformer inrush current describes a spike in current that occurs when you initially turn on your transformer. This spike can be up to 10 times higher than normal current. Why does inrush current occur? It can happen because large transformers demand a huge amount of … Continue Reading


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