IEC Manual Starters

FAQs

Do electromechanical protection devices protect against phase failures?

No, electromechanical protection devices, such as thermal overload relays found in manual motor starters, do not provide protection against phase failures. Their primary function is to protect the motor against overloads, which occur when the motor draws excessive current for an extended period.

Can short circuits cause motor overload conditions?

Yes, short circuits can cause motor overload conditions. When a short circuit occurs in a motor's power circuit, it can lead to a rapid increase in current flow, causing an overload condition.

Can manual motor starters effectively protect three phase motors?

Yes, manual motor starters can effectively protect three-phase motors. They are commonly used in various industrial and commercial applications to control and safeguard motors, including three-phase motors.

Does a manual motor starter include a circuit breaker?

Yes, a manual motor starter can include a built-in circuit breaker as part of its design. It incorporates a circuit breaker function to protect the motor and associated circuitry from excessive currents.

Motor Control Basics

Motor control allows operational control of electrical motors in various environments. 

Motor control circuits provide a safe way to operate electrical motors. Back when motor control circuits were in their infancy, it would have been common to see a simple disconnect switch that would be used to turn on and off a motor. Depending on the size of the motor and how much voltage was required, operating this disconnect would have been dangerous, with a very high possibility of arcing or electrocution. Not to mention that when the disconnect was actuated, the large amount of inrush current would have damaged the motor over time.

In today's motor control circuits, there are a few common pieces of hardware. 

A circuit breaker is used to protect the motor and any hardware downstream. A contactor and an overload relay are connected together and function in tandem to allow for remote and safe operation of the motor. The contactor functions much like a relay, allowing for a smaller electrical circuit to remotely close the motor contacts, starting the motor. The overload relay is designed to protect the motor in the case of a prolonged overcurrent event. These two devices are wired in series, so that if the overload relay detects an overcurrent event, the contactor will open the motor contacts, shutting off power to the motor.

The other two most common types of motor control hardware are a soft starter and a Variable Frequency Drive (VFD). 

Both of these devices function in a similar way to the motor circuit with some added functions. The soft starter is designed to reduce large inrush current to the motor upon startup. This “soft starting” of the motor will prolong its life and allow for safer operation. The VFD performs the soft start functions, but also allows for speed control of the motor. This speed control is critical in many different environments and has made VFDs one of the most common and safe to use motor control circuits today.