Firmware Manual

9000X AF Drives
A-4 For more information visit: www.eaton.com
MN04004001E
August 2010
Appendix A
Parameters of Motor Thermal Protection
ID704 to ID708
General
The motor thermal protection is to protect the motor from overheating. The Eaton drive is
capable of supplying higher than nominal current to the motor. If the load requires this high
current there is a risk that the motor will be thermally overloaded. This is the case especially
at low frequencies. At low frequencies the cooling effect of the motor is reduced as well as its
capacity. If the motor is equipped with an external fan the load reduction at low speeds is
small.
The motor thermal protection is based on a calculated model and it uses the output current
of the drive to determine the load on the motor.
The motor thermal protection can be adjusted with parameters. The thermal current I
T
specifies the load current above which the motor is overloaded. This current limit is a
function of the output frequency.
The thermal stage of the motor can be monitored on the control keypad display. See 9000X
AF Drives User Manual, Chapter 5.
CAUTION
The calculated model does not protect the motor if the airflow to
the motor is reduced by blocked air intake grill.
Parameters of Stall Protection
ID709 to ID712
General
The motor stall protection protects the motor from short time overload situations such as
one caused by a stalled shaft. The reaction time of the stall protection can be set shorter than
that of motor thermal protection. The stall state is defined with two parameters, ID710 (Stall
current) and ID712 (Stall frequency limit). If the current is higher than the set limit and output
frequency is lower than the set limit, the stall state is true. There is actually no real indication
of the shaft rotation. Stall protection is a type of overcurrent protection.