INDUSTRIAL OR AGRICULTURAL STARTERS

An electric motor starter is a device that controls the use of electric power to various appliances with high energy demands. They are connected to electric motors and are operated through on and off switches. They act as ‘safety switches’ on large motors with unmanageably high consumptions. However, these electric starters can be operated through automatic operation as well.
This starter switch, with suitable rating contactors and premium overload relays, provides complete protection to the starter motor from fault, hence is apt for industrial or agricultural purposes.

Why Install a Starter?

1. Provides reliable overload relays.
2. Comes with a digital screen indicating “On” or “Trip” state of
operation.
3. Provides short circuit protection.
4. An ammeter with the suppressed coil to withstand a very high starting current.
5. An automated selector starter switch.

Protections it Provides

• Overload protection
• Phase reversal protection
• Single phase protection
• Autostart with ON delay
• Phase unbalance protection

STARTERS APROPOS TO INDUSTRIAL OR AGRICULTURAL APPLICATIONS

Direct Online Starter

Direct On Line Starter switch is best suited for large starting current demands. It is compact, thus does not take up more space. Its construction is simple. It works best when connected to generators with a voltage dip ranging between 10-15%.

Starting Method:

DOL starter is the most economic and popular method of starting squirrel cage induction, starter motors wherein the starter is directly connected to the supply. Generally, the magnitude of the starting current initially is as high as six to eight times that of the rated current.

Advantages:

• Shorter starting time
• Simple construction and wiring
• High starting torque
• Compact, hence space-saving.

Disadvantage:

High starting current

Mechanically harsh

Applications:

The only operational condition for a DOL starter to work is that the high inrush current of the starter motor is not causing excessive voltage dip in the supply circuit.
Used for agricultural water pumps, compressors, conveyor belts, fans, etc.

Construction:

A 3TS3 contactor wields a 10 HP DOL starter. The design of the contractor is such that it fits well for agricultural and industrial usage. A special wideband coil (voltage ranging from 200 V to 400 V) is designed to operate even under wide voltage fluctuations.

BI -Metal Overload Relay

A 3UW5 bi-metal overload relay is fitted with a DOL starter. They are automatic and come with a fully graduated computer calibration. This feature ensures accurate protection of the motor. It has built-in single phasing protection besides overload protection. It also has an automatic reset function with a cooling time of about four seconds.

Operation:

Generally, a bi-metal overload relay system is coupled with a DOL starter. Once the starter is pushed ‘ON’, the contactor coils are energized switching on the circuit. When pushed ‘Off’, the contactor coils are de-energized and the circuit is switched off. The bi-metal overload relay has no role to play under normal circumstances. It works under overload, single phasing, or locked rotor conditions of the motor starter. When under the mentioned situations, the relay cuts off the power supply to the contactor coils, thus tripping the circuit. The contractor slips into the “No voltage” mode in case of supply failure as the circuit switches off. To restart the power supply, the “On” push button is to be pressed again.

Features:

• Computer calibrated relays.
• Accurate protection under single phasing or overload.
• The contractor coils used in it ensures longer electrical and mechanical life of the motor starter.
• Unwanted operations are halted since resumption needs manual switching on of the push button.
• With a 200 V to 400 V voltage range, the relay can easily handle huge voltage fluctuations.

Automatic Star Delta Starter

Automatic Star Delta starters are apt for induction motors with a power capacity of about 10 kilowatts. They are even simpler in construction than DOL starters consisting of only three electrical contactors, one overload protection device, and a timer. The windings are Star connected reducing the starting current, voltage, and starting torque leading to lower current inrush.

Advantages:

Low starting current.

Disadvantages:

• Low starting torque
• Longer starting time
• Needs more space

Construction:

It consists of an automatic star delta starter, contractor, and an overload relay.

Operation:

A timer manages the changeover from star to delta as per the pre-set time in the direct online starter.

Brands To Look For

Click here to buy Siemens products.

Click here to buy Schneider products.