# Frequent question: How does frequency affect motor speed?

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## How does frequency control motor speed?

A variable frequency drive controls the motor speed by using PWM (Pulse Width Modulation) to alter the power supply frequency that’s fed to the motor. There is typically no feedback coming back from the motor; although some drives uses back EMF as feedback.

## What is the relation between motor speed and frequency?

The operating speed No = N – Ns where Ns is the slip speed. The frequency of the rotor current fr = Ns x P/120, so fr = 0 if the slip is zero. If the operating speed is zero, Ns = N and the frequency of the rotor current is the same as the frequency of the stator current.

## How does frequency affect motor current?

An AC motor stator is an inductance. In an inductance, the lower the frequency, the lower its impedance. So having constant voltage over it, the current will rise if the frequency gets lower.

## How does frequency affect RPM?

If you have an electrical frequency of 50 Hz, your maximum speed is N = 60*50/1 = 3’000 rpm. You can of course increase the frequency, and thus increase N, up to a certain point!

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## When the frequency is increased the speed of the motor is?

Speed of the induction motor is proportional to the frequency. So if the frequency is increased to 100 Hz, speed will increase to twice the speed at 50 Hz.

## How do you control motor speed?

Thus, the speed of a DC motor can control in three ways:

1. By varying the flux, and by varying the current through field winding.
2. By varying the armature voltage, and the armature resistance.
3. Through the supply voltage.

## How can we increase the RPM of motor?

The speed of rotation of the coil can be increased by:

1. increasing the size of the current;
2. using a stronger magnet;
3. increasing the number of turns of wire in the coil;
4. reducing friction between the coil and the axel it rotates on.

## What is frequency in motor?

Frequency is the rate at which current changes direction per second. It is measured in hertz (Hz), an international unit of measure where 1 hertz is equal to 1 cycle per second. Hertz (Hz) = One hertz is equal to one cycle per second. Cycle = One complete wave of alternating current or voltage.

## How does frequency affect power?

If the frequency rises, the turbine reduces its steam flow. If it falls it will increase, changing the electrical output – a change that needs to happen in seconds. In the case of generating units at Drax Power Station, the response starts less than a second from the initial frequency deviation.

## What can cause a motor to run slow?

Low Resistance

Low resistance is caused by the degradation of the insulation of the windings due to conditions such as overheating, corrosion, or physical damage. This leads to insufficient isolation between the conductors or motor windings, which can cause leakages and short circuits, and eventually motor failure.

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## Is rpm same as frequency?

Revolutions per minute (abbreviated rpm, RPM, r/min, or r·min1) is a unit of frequency: the number of full rotations completed in one minute around a fixed axis.

## Can a 60hz motor run on 50hz?

For a generic answer: yes you can, IF: you reduce the voltage by 50/60, the equipment doesn’t care, you don’t care about potentially overheating the motor, the process/load can tolerate the lower speed/torque, etc.