Resistive load

Inductive Load

Load which consumes only active power is called as resistive load. And if you look at the voltage and current waveforms of such load, you’ll find that, the voltage & current are perfectly in phase with each other.

Both the waveforms reaches their peak value at the same time. They also reaches the zero value at the same time. One example is shown above.

As such type of load only consumes active power, power flows from Source to load only. There will be no power flowing from Load to source. Yes, in few cases power also flows from load to source, which I have explained in my active reactive & apparent power video.

Load which consumes only reactive power is called as inductive load. And if you look at the voltage and current waveforms of such load, you’ll find that, the voltage & current are out of phase with each other by 90 deg.

Both the waveforms reaches their peak value at different times. They also reaches the zero value at different times. If you look at the waveform you’ll find that voltage has head start then the current. We can also say current is lagging behind the voltage.

As such type of load only consumes reactive power, power can flow from Source to load or even load to source. Further, power factor of such loads is not Unity! Power factor of such loads is lagging in nature. And which is not a very good sign.

Properties of Resistive Load

Let’s see what are the properties of resistive load

• This loads consumes only active power
• Voltage & current waveform of such loads are perfectly in phase with each other.
• Power factor of such load is unity
• Power always flow from source to load

Properties of Inductive loads

Let’s see what are the properties of inductive load

• This loads consumes only reactive power
• Voltage & current waveform of such loads are out of phase with each other by 90 deg.
• Power factor of such load is lagging
• Power flows from source to load and load to source

This type of loads are not easy loads as the resistive loads. They creates lot of problem in the system. But of course they are equally important. Since, current lags behind the voltage by 90 deg in such type of loads, that makes switching of such load difficult. As we know, circuit breaker opens at current zero condition. If you look at the current & voltage waveforms of such load you’ll find that, when current is zero, voltage is maximum.

And hence, when circuit breaker opens at current zero, voltage across the breaker contact is maximum. Whereas, in case of resistive load both current & voltage becomes zero at same time. Therefore, switching such type of inductive loads is critical.

Such type of load also affects the power factor of system heavily.

Example of Resistive load

• Lights
• Heaters

Or any other loads that consist of only heating elements. Those are the examples of resistive load.

Example of Inductive Load

Let’s see few examples of inductive load.

• Electric Motor
• Fans
• Washing machine, or anything that has a motor inside it.

Also, Reactors used in power system is an example of inductive load.