# Motor voltage and current relationship

### Relation between motor's torque/speed and its voltage/current. - Doswa

Current imbalance can occur for a variety of reasons – high-resistance connection, low loading, dissimilar cable sizes, transformer anomalies, winding failures. DC Motor Speed: Voltage and Torque Relationships First, the current is constant which means the inductor can be removed; Secondly, as there is no change. DC motor operation is simple. When a coil is placed in a magnetic field and current is passed through, torque is produced, causing the motor to.

## Calculations

That is a correct statement. Dropping the voltage will reduce the speed, not the available torque.

In order to maintain the same power output at half speed one must double the torque. This may or may not be possible due to 1 the load, 2 the motor and 3 the power source. Those three issues, one at a time: The load type connected to the shaft will determine if the torque required will change with speed. I don't know what the OP's load is so here are the three basic load types. Constant torque A load where the torque required is independent of the speed applied.

### Current and voltage relationship in an electric motor | Physics Forums

A material conveyor or screw feeder are examples. The power required is linearly proportional to speed since torque remains constant. Variable torque Sometimes referred to as Quadratic torque.

The most common example would be a fan or propeller and most pumps. Speed, torque, power and efficiency of the motors are not constant values. Usually the manufacturer provides the following data in a table like this one sample data from one of the motors used in generator kit: Also the manufacturers usually provide power curves for the motor at nominal voltage: These curves are generated by plotting motor speed, consumed current, and efficiency as functions of the motor torque.

Sometimes there might be also a curve representing mechanical output power. As you can see from the graph speed and current are linear functions of torque so you might need only two measurements to draw these graphs.

Motor Torque, Speed and Current

Efficiency and power will need more data. While it is technically better to follow the same format and create similar curves for your motor it is not absolutely necessary for a good science project.

## The relationship between voltage and current in electric motors

You may take all measurements, calculate unknown values and plot the graphs where for example speed and torque are represented as functions of applied voltage or current etc. Simple formulas and calculations described here are essential for calculating most common motor parameters. However this is a simplified approach that does not take into consideration many factors. It's also possible to model the inherent inductance of the motor by adding an inductor in series, however for the most part I've ignored this and assumed the motor is at quasi steady state electrically, or the motor's time response is dominated by the time response of the mechanical systems instead of the time response of the electrical systems.

This is usually true, but not necessarily always true. The generator produces a back EMF proportional to speed of the motor: The current flowing through the motor can then be calculated: The torque generated by the motor is proportional to the amount of current flowing through the motor: Also, at the no load speed the motor has no torque and no current flowing through it.

When does the motor produce the most power?