COMPARATIVE ANALYSIS IN THE PERFORMANCE OF THE FH 90 SQUIRREL CAGE ALTERNATING CURRENT (AC) MOTOR USING MP1015 VARIABLE FREQUENCY INVERTER DRIVE AND NORMAL FREQUENCY SUPPLY Michael C. PACIS and Ronald B. CORPUZ School of EE-ECE-CoE Mapua Institute of Technology ABSTRACT Three-phase electric motors are very rugged machines that have to withstand almost endless abuse from end users and still continue to perform to specification. There are several variables of which end user is often unaware. Many have significant effect on the general performance of the motor like the terminal voltage and the application of various torques. In this study, the researchers will conduct experiments in determining the performance of the FH 90 Squirrel Cage Motor first by using the normal frequency supply, second with the use MP1015 Variable Frequency Inverter Drive in the input terminals and third with the aid of a thermistor in the rotor windings. In the third experiment, the researchers analyzed the effect of the temperature in the performance of the FH 90 motor by inserting a thermistor in the rotor windings. The performance of the FH 90 motor can be determined by plotting the performance curves in each experiment. These are the curves of the speed, torque, ampere, temperature and voltage. Based from the results, when running in a normal supply frequency, the speed of the FH 90 is constant and the torque is varied to obtain the desired results. Therefore, the output power, current and efficiency is in proportion to the speed and tends to drop off when the motor stalls. In the second experiment, when driven using MP1015 VFID, the torque is constant and the frequency is varied to obtain the required results. It is observe that when using the MP1015, the torque is constant when the supply frequency is varied from 48-90 Hz this is because the ratio of the voltage and frequency is constant throughout the experiment. In the third procedure, it is observed that when using MP 1015 VFID in the FH 90 motor , the torque of the load is constant and the temperature rises only from 20-30 Hz and from 80 to 90 Hz. Beyond these values, the motor experiences a rise in temperature and thus more power losses has been developed. But when the motor is expected to run in normal frequency supply, the FH 90 motor experiences constant rise in temperature from 0.1 N-m to 0.5 N-m. Thus, the motor must be provided with a cooling fan to prevent it from harmful effects of overheating. Keywords: FH 90, MP1015 Variable Frequency Inverter. INTRODUCTION Inherently, alternating current (AC) motors are not as well as suited to variable-speed applications as are dc motors, because their speed cannot be satisfactorily controlled by simple voltage variation. Reducing the supply voltage to a 60-Hz three-phase induction motor will reduce its speed-regulating ability. That is, an ac induction motor operating at reduced voltage is unable to maintain a reasonably steady shaft speed in the face of slight changes in torque demand imposed by the mechanical load (Maloney, 1986). The AC motor that will be used by the researchers is the FH90 Squirrel Cage Induction Motor. This three-phase Cage Rotor Induction Motor is probably the most frequently used of all electrical drives, especially in industrial applications at higher power levels. The popularity of this machine is due to a combination of its relatively low cost, robust construction, compact size, reliability and minimal servicing/maintenance requirement (MP1015 Manual, 2000). In the Electrical Engineering Laboratory of Mapua Institute of Technology there is equipment called the MP1015 Variable Frequency Inverter Drive (VFID). This Variable Frequency Inverter Drive was developed to provide with the equipment and facilities, which are necessary to investigate and understand the principles involved with practical frequency inverter drives. One of the equipment, which is compatible with the MP1015 VFID is the THQ MK1V Electrical Machines Test Bed that serves as the main supply of voltage and torque for the FH 90 AC motor. The MP1015 VFID can be substituted for the three phase input to control the speed of the AC induction motor at constant torque. The major problem of the AC induction motor is its limitation to many applications. One of them is that the speed of rotation is dependent upon the mains supply frequency. Since the mains supply frequency is fixed, normally 50 to 60 Hz, the speed of rotation is considered to be constant. Another important consideration to be made when operating an induction motor is the cooling of the windings and bearings when there is a sudden increase of loading. As the load of the motor increases, the (I 2 R) losses will be taken into account and will greatly affect the motors efficiency (Honeywell, 2000). Thus, a cooling