Motor Starter Switches | Basic Fundamentals to Understand

Motor Starter Switches | Basic Fundamentals to Understand

Posted on January 2023, By Wipro

Many electrical control systems are built on motor controls, particularly motor starters. We've put together this piece devoted to the fundamentals of a motor starter switch to help you understand the different types of starters, what they are, how they function, and why we use them. Similar to a relay, a motor starter switch power on and off. However, unlike a relay, a starter protects against overcurrent and low voltage as well. 

A motor starter has 4 fundamental functions: 

  • Starting a motor in a safe manner. 
  • Stopping a motor safely. 
  • Protecting the motor from low voltage and overcurrent. 

The typical motor starter comprises two parts that cooperate to safeguard and manage the motor. 

  • Electrical Contactor: This device turns on and off the motor's power source by forming or breaking the contact terminals. 
  • Relay for Overloads: Checks the current for overload conditions. 

Why do we Use a Starter Motor? 

Electric motors are classified as an inductive load, which requires enormous power to get up to speed and relatively little power to maintain that speed. Even though it is a short surge of power, the inrush current can be several times the steady-state current. Motors are designed to handle this inrush current and can be started and stopped without harm. 

The repeated inrush from starting across the line could overload and damage a motor in applications that require multiple starts/stops (usually more than four per hour). 

It is possible to damage other equipment attached to the supply line due to dips in voltage caused by large motors. As a result, most larger motors are started using a different method (RVSS soft starters or VFD variable frequency drives, discussed separately). It is important to stagger the start of several smaller loads by using on-delay timers or programming the control system if several smaller loads are coming online simultaneously. 

How a Starter Works? 

A single-phase motor starter switch can be manual or electromechanical. For example, a manual starter can be turned on by lifting the ON/OFF lever or button, whereas a switch controls an electromechanical starter. In applications where a manual starter is used, you'll see that it will turn off or on the power source when the ON or OFF switch is changed from that position.  

A bimetal strip inside the starter switch acts as an overcurrent protection mechanism. During higher current flow, the bimetal strip bends and activates a trip lever which cuts off the power to the connected motor device ensuring protection to the appliance. 

But one might ask, when do such events occur. A very common scenario is when the work done with the appliance is far higher than the rated tolerance of the machine. An example could be running the water pump when the water is mixed with sludge which increases the overall viscosity of the liquid. Another example could be switching on AC when there is debris present in the chamber of the outside condenser unit fan. 

Another scenario could be usage of the appliance during low voltage conditions. This is particularly dangerous as the user might not always be aware of the low voltage condition at home. Low voltage results in abnormal current drawn by the appliance which can permanently damage the unit.  

Motor Starters from Wipro North-West 

Our motor starters are the epitome of dependability since they guard your home's electrical motors and circuits against overload. Our distribution accessories give an additional layer of security to the circuitry in your home by effectively and efficiently distributing electricity. You can rely on our Distribution Accessories to provide the support required to prevent unwelcome surges or short circuits that could endanger your infrastructure. 

If you are looking for distribution accessories (e.g., single phase motor starter switch) for your home or office, you should explore our website for some great products.