ABB ACS 800 Series, Firmware Manual

Page: 75 / 340

Program features
75
Motor thermal protection
The motor can be protected against overheating by activating the Motor thermal
protection function and by selecting one of the Motor thermal protection modes
available.
The Motor thermal protection modes are based either on a motor temperature
thermal model or on an overtemperature indication from a motor thermistor.
Motor temperature thermal model
The drive calculates the temperature of the motor on the basis of the following
assumptions:
1) The motor is at the estimated temperature (value of 01.37 MOTOR TEMP EST
saved at power switch off) when power is applied to the drive. When power is
applied for the first time, the motor is at the ambient temperature (30 °C).
2) Motor temperature is calculated using either the user-adjustable or automatically
calculated motor thermal time and motor load curve (see the figures below). The
load curve should be adjusted in case the ambient temperature exceeds 30 °C.
Use of the motor thermistor
It is possible to detect motor overtemperature by connecting a motor thermistor
(PTC) between the +24 V DC voltage supply offered by the drive and digital input
DI6. In normal motor operation temperature, the thermistor resistance should be less
than 1.5 kohm (current 5 mA). The drive stops the motor and gives a fault indication
if the thermistor resistance exceeds 4 kohm
.
The installation must meet the
regulations for protecting against contact.
Settings
Parameters 30.04 to 30.09 .
Note: It is also possible to use the motor temperature measurement function. See
sections Motor temperature measurement through the standard I/O interface on
page 81 and Motor temperature measurement through an analogue I/O extension on
page 83 .
Motor
100%
Temp.
63%
Motor thermal time
t
t
100%
50
100
150
Zero speed load
Motor load curve
Break point
Motor
Speed
Load
Current
(%)
Rise