Delta 28-299A Instruções de Operação descarregar pdf (Página 30)

5 Application Examples

5.1 Motor Overload Protection

The thermal model used for motor overload in the MCD 500

has two components:

•

Motor windings: These have a low thermal capacity

and affects the short term thermal behaviour of the

motor. This is where the heat is generated by the

current.

•

Motor Body: This has a large thermal capacity and

affects the long term behaviour of the motor. The

thermal model includes considerations for the

following:

•

Motor current, iron losses, winding

resistance losses, motor body and

winding thermal capacities, cooling

during run and cooling at standstill.

•

The percentage of the rated capacity of

the motor. This sets the displayed value

for the winding model and is affected by

the motor FLC setting amongst others.

NOTE

Par. 1-1 Motor FLC should be set to the motor's rated FLC. Do

not add the overload rating as this is c

omputed by the

MCD500.

The thermal overload protection used in MCD500 has a

number of advantages over the thermal relays.

•

The effect of fan cooling is accounted for when the

motor is running

•

The actual full load current and locked rotor time

can be used to more accurately tune the model.

The thermal characteristics of the windings are

treated separately from the rest of the motor (ie.

the model recognises that the windings have low

thermal mass and high thermal resistance).

•

The winding portion of the thermal model

responds very rapidly compared with the body

portion, meaning the motor can be run closer to its

safe maximum operating temperature while still

being protected from thermal damage.

•

The percentage of motor thermal capacity used

during each start is stored in memory. The starter

can be configured to automatically determine

whether or not the motor has sufficient thermal

capacity remaining to successfully complete

another start.

•

The memory function of the model means that the

motor is fully protected in “warm start” situations.

The model uses data from the real time clock to

account for elapsed cooling time, even if control

power has been removed.

The overload protection function provided by this model is

compliant with a NEMA 10 curve, but will provide superior

protection at low levels of overload due to the separation of

the winding thermal model.

100 200 300

100

1000

10000

177HA596.10

Time in seconds to reach 100% of thermal model

Current (%motor full load current)

400 500

600 700

800 900 1000

MSTC

= 5

MSTC

= 10

MSTC

= 20

MSTC is the Motor Start Time Constant and is defined as the

Locked Rotor Time (par. 1-2) when the Locked Rotor Current

is 600% of FLC.

5.2 AAC Adaptive Acceleration Control

AAC Adaptive Acceleration Control is a new form of motor

control based on the motor's own performance character-

istics. With AAC, the user selects the starting or stopping

profile that best matches the load type and the starter

automatically controls the motor to match the profile. The

MCD 500 offers three profiles - early, constant and late

acceleration and deceleration.

AAC uses two algorithms, one to measure the motor's

characteristics and one to control the motor. The MCD 500

uses the first start to determine the motor's characteristics at

Application Examples MCD 500 Operating Instruction

MG.17.K3.02 - VLT

is a registered Danfoss trademark 29

5 5

1 2 ... 25 26 27 28 29 30 31 32 33 34 35 ... 76 77

Comentários a estes Manuais

Sem comentários

Delta 28-299A Instruções de Operação Página 30

Comentários a estes Manuais

Manuais e produtos relacionados com Serras circulares Delta 28-299A