Soft Starter, Help Minimize Cost by Reducing Overall System Power

Drive Technology basics: Soft Starter and Variable Frequency Drive

Industrial electrical equipment are usually heavy, bulk sized machineries for large-scale production. Due to their relative size and capabilities, it is often not possible to have short maintenance duration time, let alone the economical cost of ceasing or reducing production.

One the main causes of maintenance is power surge, which industrial electrical equipment are very prone to. Apart from voltage regulator, another device is required to control the electricity current going into the equipment to improve their durability.

Soft Starter
A soft starter is a device used with AC electrical motors to temporarily reduce the load, torque, and electric current surge of the motor during start-up. Soft starter reduces the mechanical stress on the motor and shaft, as well as the electrodynamic stresses on the attached power cables and electrical distribution network. Reducing the power reduces potentially damaging electrical and mechanical shocks on the system and helps extends the lifespan of the system. Soft startercan also stop, reverse, accelerate and protect electrical equipment. From a small fan a large piece of industrial electrical equipment, electric motor is the driving force behind them.
A soft starter is made up of a combination of a controller and overload protection.

• CONTROLLER – turns electric current to the motor on and off. An electromagnet controls the controller called a contactor.
• OVERLOAD PROTECTION – protects a motor from drawing too much current and overheating or “burning out”. The overload relay is the motor overload protection used in soft starters. It limits the time the overload current drawn and protects the motor from overheating.

Soft starter sits between the motor and the incoming utility line to regulate the amount of current fed to the motor. It enables the AC induction motor to gradually increase in speed compared with a traditional motor starter. Soft starter draws less current. As the voltage decreases, torque is also reduced resulting in a soft, or easy start. All types of AC and DC motors use soft Starters because of their simplicity, ruggedness and reliability.

A soft starter continuously controls the three-phase motor’s voltage supply during the start-up phase. This way, the machine’s load behavior adjusts the motor speed. Mechanical operating equipment accelerates smoothly. This lengthens service life, improves operating behavior, and smooths work flows.

Variable Frequency Drive
A Variable Frequency Drive (VFD) is a type of motor controller that drives an electric motor by varying the frequency and voltage supplied to the electric motor. Other names for a VFD are variable speed drive, adjustable speed drive, adjustable frequency drive, AC drive, microdrive, and inverter.

Variable frequency drive are sometimes called “Inverters” because of its last stage of processing electricity… commonly referred to as a “power inverter” because you are generating AC power using DC as the power source. Therefore, you are “inverting”. Variable frequency drive is sometimes also called a 3 phase inverter.

Frequency (or hertz) is directly related to the motor’s speed (RPMs). In other words, the faster the frequency, the faster the RPMs go. If an electrical application does not require its electric motor to run at full speed, variable frequency drive is useful in controlling down the frequency and voltage to meet the requirements of the electric motor’s load. As the application’s motor speed requirements fluctuate, the VFD can simply turn up or down the motor speed to meet the speed requirement.

The first stage of a Variable Frequency Drive or VFD is the Converter. The converter is comprised of six diodes, very much similar to check valves used in plumbing systems. The diodes allow current to flow in only one direction.

Why use a VFD?
1. Reduce Energy Consumption and Costs
Whenever there is an application that does not need to run at full speed, you can cut down energy costs by controlling the motor with a variable frequency drive. This is one of the benefits of a Variable Frequency Drive. The device allows you to match the speed of the motor-driven equipment to the load requirement. There is no other AC electric motor control method that permits this type of performance.

Electric motor systems are responsible for more than 65% of the power consumption in industry today. You can reduce energy consumption in your facility by as much as 70% by optimizing motor control systems. Installing or upgrading to VFD can achieve lower energy consumption. Additionally, the utilization of VFD improves product quality and reduces production costs.

2. Increase Rate of Production Through Tighter Process Control
By operating your motors at the most efficient speed for your application, you will get fewer mistakes, which will increase rate of production. This may ultimately mean higher company revenue. If you use conveyors and belts, a Variable Frequency Drive helps eliminate jerks on start-up allowing high throughput.

3. Prolong Equipment Life and Reduce Maintenance
Equipment and other machinery will last longer and have less downtime caused by maintenance. VFD’s control ensures optimal motor application speed and ideally controls the motor’s frequency and voltage. VFD will offer better protection for your motor from issues such as electro thermal overloads, phase protection, under voltage, overvoltage, etc. When you start a load with a VFD you will not subject the motor or driven load to the “instant shock” of across the line starting, but can start smoothly, thereby eliminating belt, gear and bearing wear and tear.

A Mactron specialist can help you determine Drive Technology that is suitable for you.