Electronic Soft Starters

Soft starting and soft stopping of three-phase induction motors at powers up to 800 kW

Applications

Pumps

Fans and compressors

Conveyor belts

Grinding machines, saws

Fast and heavy-duty conveyor systems

Drives using pole-change motors

Machines with gearbox, belt or chain drives

User benefits

• Reduced cost of transmission components
  • Low starting torque
  • Starting torque adjustable to requirement
• Reduced maintenance costs
  • Low starting torque reduces belt slip
• Lower repair cost
  • Fatigue effects reduced (Star/delta, transformer and single-phase starting cause high torque peaks)
• Machine protection
  • Electronic overload trip (with OPTION LS-I1)

Electrical

• Low starting current
  • Advantages compared with star/delta
  Low maintenance costs
  • Low-loading of contactor contacts with zero-current switching
• Only two voltage ranges
  • 3AC 110...500 ±10% V
  • 3AC 220...690 ±10% V

Features

An external bridging contactor can be used to reduce losses

Shutdown on detection of phase failure during ramp up

Can be combined with electronic d.c. injection brake (refer to technical manual LEKTROMIK B4)

OPTION LS-I1 provides for:
Current limit during ramp-up with switch-on pulse, monitoring of power with overload trip (stall protection), power factor improvement at low load special circuit to damp drive oscillation (e.g. with pumps), energy saving circuit for lightly loaded drives

OPTION LS-I2 provides for:
Current limit during ramp-up, start monitoring, optimised operation with pumps

OPTION LS-N provides for:
Closed-loop speed control for load-independent starting, operation for pumps

Principle of operation

The following alternative LEKTROMIK soft starters can be supplied:

• S2 in the conventional standard connection in series with the motor
• SD2 connected within the delta motor winding

Advantage:

• high motor power for same soft-start current

The modes of operation "Soft Start" and "Soft Stop" make use of thyristors in a fully controlled connection. The three thyristor pairs vary the voltage applied to the motor using phase control. The torque of the motor can be varied over a wide range.

The motor voltage increases as ramp function during soft start.The starting voltage ( = switch-on voltage) and the inclination ( = acceleration) are adjustable within a wide range. A monitoring signal "End of Ramp" indicates the end of ramp up.

With soft stop operation the voltage can be reduced to zero as a ramp function. This can prevent a load with a large frictional component from stopping too abruptly.The main contactor is opened with zero current on completion of ramp down. This provides a considerable increase in the life of the main contactor.

Available Types

Available Types		LEKTROMIK S2	LEKTROMIK SD2
Motors	Three-phase induction motors, no. of connection cables	3	6
	Pole-change motors
	Slip-ring motors	Refer to supplier	Refer to supplier
Modes of operation	Soft start
	Soft stop
	Regen. Braking n>ns
	Electronic braking with:	LEKTROMIK B4	Refer to supplier
Features	Phase control	3 PH. W3C	3 Ph. Delta
Functions	Operation with bridging contactor
	Current limit with	OPTION LS-I1/2	OPTION LS-I1/2
	Switch-on pulse, overload trip, power factor improvement, ...with	OPTION LS-I1	OPTION LS-I1
	Closed-loop speed control,  -operation	OPTION LS-N	OPTION LS-N
	Electronic contactor operation		Refer to supplier
Power range at rated voltage		1.1...800 kW/ 3AC 250...500 V	7.5...1300 kW/ 3 AC 250...500 V

Typical installations

• Centrifugal pumps in the water and sewerage industry – elimination of water-hammer problems
• Fans – reduction of high starting current, V-belt wear and starting noise
• Screw compressors – starting with minimum starting current
• Oil pumps – starting on oil rigs with a DG supply
• Bow thruster starting – starting with minimum current on a ship DG supply
• Speed-change agitators in sewerage plant – shock-free starting and speed change of pole-change motors
• Piston compressors, Circular saws – starting with minimum starting current
• Refrigeration compressors on ships – soft start with minimum starting current
• Heavy duty conveyor belts in power stations – smooth starting with minimum loading on belt material
• Mills – starting and positioning stop at loading position
• Reverse-flow heat exchangers in power stations – 400, 500 and 690 V installations
• Mixers, Extruders, Stone crushers – soft start and electronic shearp on overload

Available Types
LEKTROMIK 4...37S2/55SD2
up to 45/75 kW 

LEKTROMIK 75S2/110SD2
up to 90/132 kW

BC operation with bridging contractor

LEKTROMIK 160...800S2/250...1300SD2
up to 800/1300 kW

Options

Product conformance