Eaton M-Max Series Operating Instructions Manual

Also see for MMX11 Series: Installation instructions User manual

Contents

04/10 MN04020001Z-EN Parameter menu (PAR)97Heat protection of the motor (P8.6 – P8.9)The temperature model is based on the assumption that the motorachieves a winding temperature of 140°C at rated speed and anambient temperature of 40 °C, with 105 % rated load.The cooling efficiency, without external cooling, is a function ofthe speed (corresponding with the output frequency of thefrequency inverter). When the motor is stationary (zero frequency),heat is also dissipated through the housing surface.When the motor is under a great load, the current required by themotor can be higher than the rated operational current. Thecurrent provided by the frequency inverter can be higher than therated operational current of the motor. If the load requires thismuch current, there is a danger of a thermal overload. This isespecially the case at lower frequencies (< 25 Hz). Here, thecooling effect (speed of the motor fan) and the load rating of themotor (see data sheet of the motor) are reduced similarly withlower frequencies. On motors that are equipped with an externalfan, there is less of a load reduction at lower speeds.With parameters P8.6 to P8.9, a motor temperature protection canbe set for the frequency inverter M-Max TM which protects themotor from overheating. The temperature protection is calculated.A direct temperature measuring in the windings of the motor (seethermistor protection) offers great protection.The reaction of the M-Max TM frequency inverter to a detectedthermal overload can be set via parameter P8.6. At parameterP8.8 you can set the cooling output (PCool ) on the motor at zerofrequency (standstill). Note here the specifications of the motormanufacturer.Possible setting values are 0 to 150 % of the cooling output at therated frequency fN (see nameplate of the motor = P7.6).The thermal current Ith corresponds with the load current atmaximum thermal load rating on the motor. In continuousoperation, at rated frequency (fN = P7.6) and rated loading, thevalue of Ith corresponds with the rated operational current of themotor (see rating plate of the motor = P7.1).The time constant for the motor temperature (P8.9) defines howlong it takes until the temperature has achieved 63% of its endvalue in the motor. In practice, this temperature time is constantdepending on the type and design of the motor. It varies betweenthe different design sizes at the same shaft power and betweenthe different motor manufacturers.The larger a motor is, the greater the time constant.The factory set value (P8.9 = 45 min) can be set in the rangebetween 1 and 200 minutes. The guide value is twice time t 6 of amotor. The t 6 time defines the time in seconds in which a motorcan be operated safely at six times the rated operational current(for this see data sheet of the motor, manufacturer specifications).If the drive is stopped, the time constant is increased internally tothree times the set parameter value (P8.9).h The motor temperature protection is based on acalculated temperature model and uses the motor currentset in parameter P7.1 to determine the motor load. It doesnot use a temperature measurement in the motor.h Caution!Debounced inputs may not be used in the safetycircuit diagram.The calculated temperature model cannot protect themotor if the cooling flow to the motor is influenced, by ablocked air entry-way for instance.h If the protection function is deactivated (P8.6 = 0), thetemperature model of the motor is reset to zero.Figure 86: Motor cooling powerFigure 87: Calculation of motor temperaturea Motor current I/I Tb Trip value shut-off (error message) or warningaccording to P8.6c Calculated value for the motor temperature Q = (I/I T)2 x (1 - e-t/T)d Motor temperature M (example)P8.9 = Motor temperature time constant (T)P7.6 f NP8.8100 %150 %PCoolP7.1I thf [Hz]t105 %P8.9P8.6iMabcd