03 - SSW Introduction

8/7/2019 03 - SSW Introduction

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Introduction

SOFT-STARTERS

SSW-05 SSW-04 SSW-03


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Introduction

Main methods for starting induction motor :

Direct on-line starter

Star-delta starter

Auto-transformer starter

Soft Starter


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Introduction


Advantages:

Low cost

No limit for number of starts

Reduced space at installations

M

Line

Fuses

Contactor

Thermal

Relay

Motor


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Introduction

Disadvantages:

High starting current

Drop voltages

Protecting components must be oversized (cables, contactors)

Produce torque peak

Increase maintenance and mechanical damages



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Introduction

Star-delta starter

Advantages:

Low cost

No limit for number of starts

Reduced space at installations

Starting current reduced to 1/3 nominal

starting current (Is/In)M


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Introduction

Disadvantages:

6 terminals box is required

Line voltage = phase voltage in star configuration

Motor must reaches at least 90% its rated speed in the start

H

igh current spike when switching from star to delta

Starting torque reduced to 1/3 nominal starting torque (Ts/Tn)

Star-delta starter


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Introduction


Advantages:

The motor is not disconnect when the

auto-transformer is passing by. The

second spike is low.

Variable (changeable) starting voltage(transformer taps) - 65 to 90% line voltage

M


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Introduction

Disadvantages:

Number of starts is quite limited

High cost due to the auto-transformer

High weight and size due to the auto-transformer000



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Introduction

Soft-starters use SCRs to regulate the amount of

voltage app

lied to the motor. It provides the minimumamount of voltage necessary to develop the required

starting torque.

That voltage is then increased via a programmable

ramp thereby providing the motor with a smoothstarting torque and stepless ramp to full speed while

still providing constant torque up to 500% of the

motors full rated current.

Soft-Starter(Solid State Reduced Voltage Starters)


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Introduction

Soft-Starter(Solid State Reduced Voltage Starters)

Advantages:

Smooth start - electrically and mechanically - reduction of shock

and wear on the mechanical components

Local (keypad) or remote human-machine-interface

Full motor protection

Features available only in the WEGSoft-starters:

Pump Control- minimises the Water HammerWater Hammer

Kick Start - to high inertia load (e.g.: compressors)


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Introduction

The systems productivity and uptime can be greatlyincreased by reducing the costs associated with

maintenance, downtime and parts replacement!

Why Use ASoft Starter ?

Provides electrical and mechanical soft starts to a load

No moving parts to break

No contacts to wear out

No arcing contacts orlarge coils to induce spikesb


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Introduction

Reduce/limit motor starting current

Gradually start running a load

Gradually stop a load

Avoid water hammer in pipe lines

Energy saving



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Introduction

Mechanical advantages

Components subject to

shock starting:


Drive Train

Shafts

Keyways

Belt

FastenersV-Belts

Sheaves

Bearings

Gearing


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Introduction

What is a Soft Start?

Customer Interface Circuitry

Gate Firing Logic

SCRFiring Circuitry

Power supply

Diagnostics

Noise and transient protection -Snubbers/MOVs

Power devices - Power Poles/SCRs

Heat Sinks and Cooling (If required)


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Introduction

Soft StarterSimplified diagram


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Introduction

Direct on-lineStar-delta

Soft-Starter

Starting methods comparison

Current

Time


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Introduction

TYPICAL SOFTSTARTERAPPLICATIONS

PUMPS- water hammer- surge and stops in the pipe FANSAND BLOWERS- high inertia and long starts

COMPRESSORS

CONVEYORS- no stress to the belts

2 MOTOROPERATION


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Introduction

APPLICATIONS

Motor Protection

Previously motors were subjected to excessive thermal

conditions that decreased the life of the motor.

Overload relays and fuses could not fully protect the

motor under multiple starting or high load conditions.


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Introduction

APPLICATIONS

Motor Protection

The electronic thermal protection class, P25 and theWEG exclusive Thermal Image Motor Protection

(TIMP), P27, takes into account all dynamic

conditions and

takes into account the specific WEG motor

characteristics to get the highest level of motorperformance while fully protecting the motor to get a

long reliable life time.

Documents

03 - SSW Introduction