# Frequent question: Can any DC motor be variable speed

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In general if you don’t do anything special to it, a DC motor will have variable speed. The main factors are the DC voltage applied to the armature coil and the amount of torque load you are trying to drive. In order to make it into a constant speed DC motor you have to have some sort of electronic feedback.

## Which DC motor is variable speed motor?

For applications where variable speeds are necessary, typically an AC motor with an Inverter or brush motors are used. Brushless DC motors are an advanced option due to their wide speed range, low heat and maintenance-free operation. Stepper Motors offer high torque and smooth low speed operation.

## Can any motor be variable speed?

– Variable frequency drives (VFDs): Variable frequency drives also control the speed of a motor, but they do so by changing the voltage and frequency and can thus only be used with AC motors. Variable speed drives supply specific amperage and voltage to a motor.

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## Can all motors be used with a VFD?

Output voltages are available for VFDs to match almost any existing motor voltage. However, very few, if any, VFDs have a direct 13,800-volt output for very high-voltage motors. For these cases, using a step-up transformer on the output of the VFD is often necessary to match the motor voltage.

## How do you vary 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 the field winding. By varying the armature voltage, and by varying the armature resistance.

## Why a dc series motor is called a variable speed motor?

The most common types rely on the forces produced by magnetic fields. Nearly all types of DC motors have some internal mechanism, either electromechanical or electronic, to periodically change the direction of current flow in part of the motor.

## How do variable speed motors work?

A variable speed drive is a device used in electromechanical drives to control the speed and torque of an AC motor by adjusting the motor’s input frequency and voltage. Variable speed drives may be either electric, hydraulic, mechanical or even electronic.

## Can you slow down an electric motor?

Slowing down a single phase AC motor can be complicated and expensive. They are usually built to be run at a certain speed and anything else would be tricking it to do something it wasn’t meant to. Simply slowing it down may cause it to overheat with reduced mechanical self-cooling.

## Can a single phase motor be variable speed?

Speed control of single-phase induction motors is desirable in most motor control applications since it not only provides variable speed but also reduces energy consumption and audible noise. Most single-phase induction motors are unidirectional, which means they are designed to rotate in one direction.

## Can a VFD damage a motor?

Shaft currents induced by VFDs can lead to motor failures. Without some form of mitigation, shaft currents travel to ground through bearings, causing pitting, fusion craters, fluting, excessive bearing noise, eventual bearing failure, and subsequent motor failure. This is not a small problem.

## Can you run a VFD without a motor?

Well, you can program the VFD without actually connecting it at output, just give the rated voltage at the input terminals and start programming. Most VFDs you can even ‘run’ with no load connected, especially if running open loop V/Hz mode.

## How can you tell if a motor is VFD?

Three major factors should be considered when determining if a motor is compatible with a VFD: the motor winding insulation, motor bearings and pump operating speed range.

## How do I choose a VFD for my motor?

1. Full Load Amperage. The first step in this process is making sure the drive can handle the motors current demands. …
3. Application Type. …
4. Altitude. …
5. Temperature. …
6. Carrier Frequency.

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

If you want to reduce rpm without compromising speed regulation then use a voltage regulator or PWM controller to lower the motor voltage. If you also want higher torque then use a gearbox (which increases torque by the same proportion as it reduces shaft rpm).

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## How do you slow down a 12v DC fan?

Get a three 1.8 ohm 2 watt resistors, connect them in parallel and put them in series with your fan (put them in the air stream of the fan to help cool them). That should slow your fan down and reduce the load.

## How do you control speed and torque of a DC motor?

To control DC motors torque, a DC drive will regulate armature current. The armature voltage is unregulated allowing the motor to operate at whatever speed is necessary to achieve the set current /torque level.