# How Can We Reduce The Inrush Current Of A DC Motor?

## How can you reduce the speed of a DC motor?

Thus, the speed of a DC motor can be controlled in three ways:By varying the supply voltage.By varying the flux, and by varying the current through field winding.By varying the armature voltage, and by varying the armature resistance..

## Why starting current is high in motor?

When 3 phase voltage applied across the stator winding for starting of induction motor, high inrush currents magnetize the air gap between the stator and rotor. An induces emf is generated in the rotor windings of the induction motor because of the rotating magnetic field.

## How long does inrush current last?

These currents can be as high as 20 times the steady state currents. Even though it only lasts for about 10ms it takes between 30 and 40 cycles for the current to stabilize to the normal operating value.

## How do you limit starting current?

Some of the techniques used to reduce the starting current of a squirrel induction motor:Soft starting (voltage control)Variable Frequency Drives (Voltage and frequency control)Star/Delta Starting.Stator impedance and/or resistance starting.Autotransformer Starting.

## How can I select NTC for inrush current limiter?

Use Equations (1) and (4) to determine the energy of the inrush current: 73.18 J needs to be safely absorbed by the NTC thermistor.Use Equation (2) to determine the minimum resistance required by the NTC thermistor: RMIN = 171.1 V / 30 A. 5.70 Ω is required from the NTC thermistor at 25 ºC.Steady-state current: 10 A.

## How can we reduce the starting current of a DC motor?

To prevent such an incidence from occurring several starting methods of DC motor has been adopted. The main principal of this being the addition of external electrical resistance Rext to the armature winding, so as to increase the effective resistance to Ra + Rext, thus limiting the armature current to the rated value.

## How can I reduce my inrush current?

Inrush current can be reduced by increasing the voltage rise time on the load capacitance and slowing down the rate at which the capacitors charge. Three different solutions to reduce inrush current are shown below: voltage regulators, discrete components, and integrated load switches.

## Why put a diode across a motor?

2 Answers. The diode is to provide a safe path for the inductive kickback of the motor. If you try to switch off the current in an inductor suddenly, it will make whatever voltage is necessary to keep the current flowing in the short term. Put another way, the current thru an inductor can never change instantaneously.

## How do you connect a breadboard to a DC motor?

Connect your DC motor to separate lines on your breadboard, one to the 5v power line, the other to connect to the middle (collector) leg of the transistor. Connect a 220-ohm Resistor from the base (left) leg of the transistor to a separate line, then from that line to your digital IO pin.

## How is inrush current calculated?

If there is a voltage difference across the switch the magnitude and frequency of this inrush current can be calculated. The magnitude and frequency of this charging current depends upon the total capacitance and inductance of the circuit as well as magnitude of the applied voltage.

## What is inrush voltage?

Inrush current, input surge current, or switch-on surge is the maximal instantaneous input current drawn by an electrical device when first turned on. Alternating-current electric motors and transformers may draw several times their normal full-load current when first energized, for a few cycles of the input waveform.

## How do I use inrush current limiter?

To limit inrush current, an NTC thermistor is placed between the power supply and system (see Figure 1). Upon power on, the NTC thermistor provides high resistance to limit inrush current. As the inrush current drops, the NTC thermistor self-heats and its resistance drops to a low enough value to pass current through.

## How can we protect DC motors?

The circuit protects the DC motor from over voltage and under voltage. A relay could be used for switching the load (12v dc motor) on and off. A comparator is used to detect if it’s either high or low. The over voltage should be 14V while the under voltage should be 10V.