RESISTIVE LOAD vs INDUCTIVE LOAD

RESISTIVE LOAD vs INDUCTIVE LOAD

An electrical load is a device connected to the output of an electrical power source. Example of electrical loads are; DVD, TV, Motor, Charger and any other things or appliance you plugged in to your house hold socket or connect to the mains supply from the distribution company (NEPA).A load is something what removes electrical power from a circuit for some purpose. It can be a lightbulb, a speaker producing sounds, a motor turning some machinery, or an antenna sending radio signals.These electrical loads are however of different type.

Types of Electrical Load

1. Resistive load: It is a type of load that draws current in the same proportion with the apply voltage. They are typically used to convert current into form of energy such as heat.


That is the voltage and current are of the same phase.
These kind of electrical load converts electrical energy to heat. Example of resistive load include:
1. Electric heater
2. Cooker
3. Incandescent bulb
4. Iron
and other appliances that uses heat for operation.
Also, as the load resistance then temperature of the device increases.

Voltage optimization is an energy saving technology that is used to regulate, clean and condition the incoming power supply in order to reduce the voltage supplied to the optimum level for the on-site electrical equipment and appliances.
They are often benefits from voltage optimization, in order to conserve power and extend the life of electronics.
Voltage optimization provides resistive loads with the optimal operating voltage and ensures consistent supply of quality power in other to prevent the effects of potentially harmful brownouts (a drop on the voltage coming from the electrical power supply) and power surges (spikes from a power supply, also known as overvoltages) that can damage increasingly sensitive equipment.
Less complex conventional resistive loads such as light bulbs can also have their consumption reduced and their operating life extended by the optimal, stable power supplied by voltage optimization.

2. Inductive Loads

An inductive load is a type of load that consume reactive power because the current now lags the voltage. Inductive loads require magnetic field to operate. So, appliances and gadgets made of coils are inductive in nature. Inductive loads take time to develop there magnetic field when the voltage is applied, so the current is delayed
Examples include rotating equipment like fans, motors etc

As the current lags the voltage the inductive load is present.
One negative effect of using an inductive is that they produce inductive discharge


To understand the behavior of inductive discharge, lets examine how an inductor actually behave with influence of supply current -
When current flows through a coil of wire (inductor/solenoid), magnetic field begin to build up in the inductor and it will get to a particular time t that the magnetic will build to maximum. When the source of supply is removed from the inductor, the magnetic field built up before will collapse and will allow emf to be induced in reverse polarity of the power supply. 
It is the discharge of this stored energy which can cause damage to the element which is switching the current on and off or can cause erratic operation of other electronic circuits. 

Lets examine the simple case of a pair of relay contacts switching a 24V DC inductive load. The diagram below shows the voltages you would measure across the coil with an oscilloscope as the relay contacts open to turn the load off.

As the contacts start to open the normal current flow through the load shuts off, and the stored inductive energy must now discharge. As the open relay contacts are a high resistance to current flow, the voltage across the load increases quickly in the negative direction (remember the reverse polarity of the stored energy) until the voltage is high enough to jump the air gap between the contacts. This is just like the arc created in spark plugs and happens in a few thousandths of a second. 
A 24V DC coil can create negative voltages as high as several hundred volts if the inductance of the load (related to the number of winding) is high enough. A 220V AC coil can create voltage spikes in the thousands of volts.
  
NEGATIVE IMPACT OF INDUCTIVE SWITCHING

There are multiple negative affects which can be created by un-suppressed inductive energy discharges. 
Relay Contacts: The primary effect on relay contacts is damage to the plating on the contacts from the arcing. This will cause shortening of the contact life and reduction of the current handling capability. 

Solid State Switches: The potential effect of the large voltage spikes produced by inductive load switching can be even more serious on solid state switches. All solid state switching devices have maximum voltage ratings beyond which immediate damage will occur. The high voltage can punch through the insulating materials used internally to protect the device and create a short circuit. This permanently damages the device thereby requiring its replacement. 
All Artisan Controls products with solid state outputs employ protection against transient voltage spikes but the protective devices used have limitations and if these limitations of voltage and transient energy are exceeded the product will still be damaged. 

Secondary Effects: The rapidly changing currents and voltages generated by unsuppressed inductive discharges produce high frequency noise which can affect other electronic devices. This electronic noise can be either tramsitted along the power and control wires of a system or can be radiated through the air. This electronic noise can interfere with the proper operation of digital and analog circuits, generally causing erratic operation or requiring the electronic device to be power cycled to restore normal operation.

Effect of Inductive Load on Power
Because of the behavior of inductor in a circuit which tends to make current drawn lag voltage such that the initial fundamental wave form has been distorted. The effect of this is induced power line harmonics which causes stress on the distribution line and causes equipment of your supply utility to begin to heat up so the supply utility (NEPA) charge you base on that which increase your tariff.