# Why is DC motor current so high

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The starting current is high as there is no back EMF or counter EMF present in the armature circuit because atstarting counter EMF is zero. … It’s armature has very less resistance due to this it need more current at starting time. Hence DC starters are used to limit the starting current ofmotor.

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

When starting the motor, instead of just setting the required pin to 1, use the PWM function and increase the duty cycle of the PWM slowly (from 0 to 100% min ca. 1-2 seconds). That should reduced the current and make the motor accelerate smoothly to its maximum velocity. You can find a tutorial here, here and here.

## How do you control the speed of a DC motor?

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

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## Why does DC series motor have high speed regulation?

The decrease of the back emf allows more current to flow through the armature causing an increase in magnetic field strength. In DC motor the speed regulation is proportional to the resistance of the armature. The lower the armature resistance the better will be the speed regulation of the dc motor.

## 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.

## Why starters are required in a DC motor?

Starters are used to protect DC motors from damage that can be caused by very high current and torque during startup. They do this by providing external resistance to the motor, which is connected in series to the motor’s armature winding and restricts the current to an acceptable level.

## When the speed of DC motor is increased?

The speed of a dc motor is changed by changing the current in the field or by changing the current in the armature. When the field current is decreased, the field flux is reduced, and the counter emf decreases. This permits more armature current. Therefore, the motor speeds up.

## How do I control my 12V fan speed?

All we need to do is insert a rheostat or variable resistor in the 12V wire to the fan. The rheostat should be rated at least 3 Watt, (for fans up to 10Watt), and have a resistance of 20 – 50 Ohms. If you are using this mod on your CPU fan then use the 20 ohm rheostat to prevent fan stall at the slowest speed setting.

## What is rated speed of dc motor?

DC controls adjust speed by varying the voltage sent to the motor (this differs from AC motor controls which adjust the line frequency to the motor). Typical no load or synchronous speeds for an AC fractional horsepower motor are 1800 or 3600 rpm, and 1000-5000 rpm for DC fractional hp motors.

## Can you reverse polarity on a DC motor?

Simply put, DC motors can turn in either direction (clockwise or counter-clockwise) and can be easily controlled by inverting the polarity of the applied voltage. Strictly speaking, the motors can actually create a force in either direction.

## Why is the DC motor preferred over AC motor?

DC motors have the advantage of: higher starting torque, quick starting and stopping, reversing, variable speeds with voltage input and they are easier and cheaper to control than AC. AC motor advantages include: lower power demand on start and minimal maintenance.

## Which DC motor has poorest speed control?

1. Which of the following DC motor has the poorest speed control? Explanation: DC series motor at no load condition gives infinite speed ideally. Practically it will damage all the armature circuit.

## Why is inrush current bad?

The ratio of inrush current to normal full-load current can range from 5 to 100 times greater. … This current surge can cause component damage and/or failure within the equipment itself, blown fuses, tripped circuit breakers, and may severely limit the number of devices connected to a common power source.

## How long is inrush current?

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.

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## How long does inrush current last?

The inrush may be as much as 14 times the steady-state current and may persist for a few milliseconds for smaller lamps up to several seconds for lamps of 500 watts or more.