To visit our library of over 750 articles on home improvement, please click:

Home Improvement

Successful Motor Protection Formulae


As we have discussed before, all overload relays have one major limitation - because they operate on line current, they do not directly sense the motor temperatures.

However, with proper heater selection and careful attention to the factors that affect heater performance, the overload relay can work extremely well to protect the motors.

Some of these factors that need close attention are:

Motor full load current
Motor temperature rise rating
Service factor
Ambient temperature at the motor and at the protector
Motor locked rotor current ratio
Starting time
Duty cycle
Locked rotor endurance time.

If attention is not given to these factors, the overload relay will perform poorly. The other factor to be considered is maintenance. Below are some maintenance routines:

Cleaning - The overload relays should be cleaned periodically. Dirt or dust created by the operating conditions in the plant tends to settle around the moving parts in the device and prevent it from operating properly.

Tightening connections - Because most overload relays make use of current flowing through heater elements to sense overloaded conditions, it is important that the electrical terminals are not loose. Loose electrical connections can create extra heat and cause false tripping of the relays.

Inspecting heater size - Heaters can oxidize over a period of time and become smaller in cross section. The smaller current flowing in the smaller heater generates the same amount of heat to cause unnecessary tripping of the relay.

With careful selection and maintenance, overload relays are excellent for motor protection.

The wide use of thermal overload relays in industry attests to their acceptance as the most practical means of protecting motors from overloads. And they are the most economical solution available.

Until next time...

"Looking For Magic Gadgets Discount?" Gifts for Curious Minds expands Our Thinking! Will it Spark the Genius in You?

Many years of working experience in Marine, Facilities, Construction has given the author material for writing e-books and articles related to engineering, and management. Subscribe to facworld ezine More information at Marine Engineer and M & E Engineer

 

 

Discount Flights - Discount Flights and Hotels

 

Cheap Car Insurance - A Guide to Buying Cheaper Car Insurance Online

Cheap Car Loans - Get a cheaper car loan by applying online

Advice Bureau - A Guide to Managing your Personal Finance

 

 

 

 

 

 

Property Handbook | Home Improvement | Home Improvement site map

mortgage calculator | cheap car loans | broadband providers

© Investment Properties