Programmable Protection Functions; Motor Thermal Protection; Motor Temperature Thermal Model; Use Of The Motor Thermistor - ABB ACS800 Series Firmware Manual

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Programmable protection functions

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:
• The motor is at the estimated temperature (value at
saved at power switch off) when power is applied to the drive. When power is
applied for the first time, the motor is in the ambient temperature of 86 °F (30 °C).
• 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 at case the ambient temperature exceeds 80 °F
(30 °C).
Motor
Load
100%
Temp.
Rise
100%
63%

Use of the motor thermistor

It is possible to detect motor overtemperature by connecting a motor thermistor
(PTC) between the +24 VDC 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
regulations for protecting against contact.
Program features
t
t
Motor thermal time
01.37 MOTOR TEMP EST
Motor
Break point
150
Current
(%)
100
50
Zero speed load
.
The installation must meet the
Motor load curve
Speed