All MGM motors are designed to be suitable for inverter duty. See below to understand the motor operating under invertercontrol: The motor speed depends on the power supply frequency. Basically the inverter works converting the power input from the line
with a fixed amplitude and frequency into a voltage supply with a variable amplitude and frequency suitable to control the motorspeed. Inverter can’t generate an output voltage higher than the input voltage while it can increase the frequency above the
input rated value; Constant torque regulation range means a range where the inverter is able to keep the nominal ratio of voltageto frequency constant; in our diagram this range is up to 50 Hz.
Constant power (or flow) regulation range means a range where the inverter can increase frequency (and so the motor rotation
speed), without voltage increase to the motor (and consequently
the torque); in our diagram this range exceeds 50 Hz;
Operating diagram shows the percent values of the torque
available both in continuous and overloading running; When
the motor is running within constant torque regulation range
(frequency below 50 Hz), it is necessary to check that continuous
slow running does not cause overheating; in that case servo
fan (see operating diagram) is needed. When the motor is
running within constant power regulation range (frequency
above 50 Hz), it is necessary to check if the torque required
by the load does not exceed the torque indicated on the
operating diagram, otherwise malfunction and eventual in-
tervention of inverter overload protection devices could occur.
T/Tn
HzRPM Vector control – Continuous DutyV/f control – Continuous DutyVector Control – Forced Cooling or IntermittentDutyV/f control – Forced Cooling or IntermittentDutyVector Control – Overloading conditions withIntermittent DutyV/f control – Overloading conditions with Inter-mittent Duty GENERAL CHARACTERISTICS The brake should be supplied separately from the motor on
brake motors controlled by
industrial inverters, to ensure the proper workingof the brake coil. In this case the double terminal board box option must be requested. On brake motors with AC brake coil, it isalso advisable to use a safety overload cutout (MGM type RC04) on the power supply of the brake coil.The starting torque of a motor running on inverter is different from the one of a motor connected directly on line. Be sure to selectan inverter with technical specifications suitable for the work load of the machine it is intended to be used on. An inverter changes the electrical wave pattern to the motor from purelysinusoid to switching typical shape. Because of undesirable harmonic
components added to the underlying power supply, a motor controlled
by an inverter has higher losses, and an increased vibration and noise
level. The efficiency reduction varies according to the type of inverter
used. In the figure on the right the harmonic content on the power
supply of a motor under inverter can be seen (blue indicates the
underlying power supply, grey indicates the harmonics).
% A 100908070
60
50
403020
10 Hz Please contact MGM technical staff when using inverters with power supply higher than 400V or when using long cables between
the motor and the inverter as both situations can be critical for the motor winding insulation system.
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