6-8 PM Motor Mode
The 3GM3MX2-EV2 Series Inverter uses the PM motor mode to enable the inverter to control of a syn-
chronous motor (PM motor), which is more efficient than an induction motor (IM motor).
This section describes the PM motor mode.
6-8-1 PM Motor and PM Motor Control
A PM motor (abbreviation for “Permanent Magnet motor”) is a motor that uses permanent magnets for
the motor rotor.
Generally, it is also called a synchronous motor. Compared with induction motors that are used conven-
tionally for the inverter, PM motors allow no current flow on the rotor side, which results in highly effi-
cient operation due to reduced loss.
In terms of the internal construction, there are various types of PM motors: IPM motors (interior perma-
nent magnet type), SPM motors (surface permanent magnet type), and so on.
PM motors have the control characteristics as shown below.
When using the PM motor mode, understand the following characteristics before selecting the Inverter
type and function settings.
•
The applied AC power must be synchronized with the rotor permanent magnets.
Although the motor allows a large current to flow, it cannot output a sufficient torque if the AC power
is not synchronized.
•
The permanent magnets used for the rotor are subject to demagnetization if a large current flows in
the PM motor.
Once rotor is demagnetized, the motor cannot output a sufficient torque and must be replaced.
The 3G3MX2-EV2 Series Inverter uses sensorless control to realize PM motor
control. This means that the inverter cannot output a large starting torque.
PM motor control is suitable for applications with reduced torque characteristics (which do not require
torque at low speeds) such as fans and pumps.
However, it cannot be used for applications with constant torque characteristics such as general trans-
fer equipment and elevating axes (which require a torque exceeding the rated torque also at low
speeds).
To keep the PM motor in a synchronized state, use the inverter with a starting torque of 50% of the
motor rated torque or lower.
Follow the steps below to use PM motor control:
(1)
Switch to the PM motor mode. (P. 6-58)
(2)
Perform offline auto-tuning for PM motor parameters. (P. 6-59)
(3)
Set PM motor parameters. (P. 6-62)
Refer to this section if offline auto-tuning fails.
(4)
Adjust the PM motor mode settings. (P. 6-64)
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