92 • vacon appendices
Tel. +358 (0)201 2121 • Fax +358 (0)201 212 205
9
9.2 Parameters of motor thermal protection (ID’s 704 to 708):
General
The motor thermal protection is to protect the motor from overheating. The Vacon 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 the product's
User's Manual.
CAUTION! The calculated model does not protect the motor if the airflow to the
motor is reduced by blocked air intake grill.
9.3 Parameters of stall protection (ID’s 709 to 712):
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.
9.4 Fieldbus control parameters (ID’s 850 to 859)
The Fieldbus control parameters are used when the frequency or the speed reference comes from
the fieldbus (Modbus, Profibus, DeviceNet etc.). With the Fieldbus Data Out Selection 1…8 you can
monitor values from the fieldbus.
!
To Next Page
Loading...
Need help?
General
