Xylem IM255 AQUAVAR Intelligent Pump Controller - Manual (Page 11)

The X-axis shows the ratio between I
motor
actual and I
motor
nominal. The Y-axis shows the
time in seconds before the ETR cuts off and trips the frequency converter. The curves
show the characteristic nominal speed, at twice the nominal speed and at 20% of the
nominal speed. The curve shows that at lower speed the ETR cuts off at lower heat due to
less cooling of the motor. In that way, the motor is protected from overheating even at low
speed. The ETR function calculates the motor temperature that is based on actual current
and speed. The calculated temperature is visible as a readout parameter in 16-18 Motor
Thermal in the frequency converter.
Motor thermal protection can also be achieved using an external thermistor. Set 1-90
Motor Thermal Protection to data value [2] Thermistor trip or data value [1] Thermistor
warning. Set 1-93 Thermistor Source to the input to which the thermistor is connected.
Refer to the examples below for wiring details.
The thermistor cut-out value is >3kΩ. Integrate a thermistor (PTC sensor) in the motor for
winding protection.
The following examples show various ways to connect the PTC/Thermistor to the drive.
• Using a digital input and the 24V as a power supply.
• Parameter set-up:
• Set 1-90 Motor Thermal Protection to Thermistor Trip [2]
• Set 1-93 Thermistor Source to Digital Input 19 [4]
Product Description
Aquavar ® Intelligent Pump Controller INSTRUCTION MANUAL 9