Specifications
For Correct Operation
Application to Motors
[Application to general-purpose motors]
Operating frequency
Torque characteristics
Motor loss and
temperature increase
Noise
Vibration
Power transmission mechanism
Gear motor
A system applying a voltage-type PWM inverter with IGBT may have surge voltage at the motor terminals resulting from the cable constants including
the cable length and the cable laying method. Depending on the surge current magnification, the motor coil insulation may be degraded. In
particular, when a 400V-class motor is used, a longer cable is used, and critical loss can occur, take the following countermeasures:
(1) install the LCR filter between the inverter and the motor,
(2) install the AC reactor between the inverter and the motor, or
(3) enhance the insulation of the motor coil.
Brake-equipped motor
Run/Stop
Emergency motor stop
High-frequency run
Pole-change motor
Submersible motor
Explosion-proof motor
Synchronous (MS) motor
High-speed (HFM) motor
Single-phase motor
[Application to the 400V-class motor]
Notes on Use
[
Drive
]
The overspeed endurance of a general-purpose motor is 120% of the rated speed for 2 minutes (JIS C4004). For
operation at higher than 60 Hz, it is required to examine the allowable torque of the motor, useful life of bearings,
noise, vibration, etc. In this case, be sure to consult the motor manufacturer as the maximum allowable rpm differs
depending on the motor capacity, etc.
The torque characteristics of driving a general-purpose motor with an inverter differ from those of driving it with
commercial power (starting torque decreases in particular). Carefully check the load torque characteristic of a
connected machine and the driving torque characteristic of the motor.
An inverter-driven general-purpose motor heats up swiftly at lower speeds. Consequently, the torque level permitting
continuous use decreases with lower motor speeds. Carefully check the torque characteristics.
When run by an inverter, a general-purpose motor generates noise slightly greater than with commercial power.
When run by an inverter at variable speeds, the motor may generate vibration, especially because of (a) unbalance of
the rotor including a connected machine, or (b) resonance caused by the natural vibration frequency of a mechanical
system. Particularly, be careful of (b) when operating at variable speeds a machine previously fitted with a constant
speed motor. Vibration can be minimized by (1) avoiding resonance points using the frequency jump function of the
inverter, (2) using a tire-shaped coupling, or (3) placing a rubber shock absorber beneath the motor base.
Under continued, low-speed operation, oil lubrication can deteriorate in a power transmission mechanism with an oil-
type gear box (gear motor) or reducer. Check with the motor manufacturer for the permissible range of continuous
speed. To operate at more than 60 Hz, confirm the machine
’s ability to withstand the centrifugal force generated.
The allowable rotation range of continuous drive varies depending on the lubrication method or motor manufacturer.
(Particularly in case of oil lubrication, pay attention to the low frequency range.) The Hitachi CX/CA gear motors are of a
grease lubrication type. Their grease lubrication capability remains unchanged even if the motor rotating speed
decreases.
For use of a brake-equipped motor, be sure to connect the braking power supply from the primary side of the inverter.
There are different kinds of pole-change motors, constant output characteristic type, constant torque characteristic
type, etc., and with different rated current values. In motor selection, check the maximum allowable current for each
motor of a different pole count. At the time of pole changing, be sure to stop the motor.
The rated current of a submersible motor is significantly larger than that of the general-purpose motor. In inverter
selection, be sure to check the rated current of the motor.
Inverter drive is not suitable for a safety-enhanced explosion-proof type of motor. The inverter should be used in
combination with a pressure-proof explosion-proof type of motor.
* Explosion-proof verification is not available for SJ100 Series. For explosion-proof operation, use other series of motors.
In most cases, the synchronous (MS) motor and the high-speed (HFM) motor are designed and manufactured to meet
the specifications suitable for a connected machine. As to inverter selection, consult the manufacturer.
A single-phase motor is not suitable for variable-speed operation by inverter drive. Therefore, use a three-phase motor.
Run or stop of the inverter must be done with the keys on the operator panel or through a control circuit terminal.
Do not operate by installing a electromagnetic contactor (Mg) in the main circuit.
When the protective function is operating or the power supply stops, the motor enters the free run stop state. When
an emergency stop is required or when the motor should be kept stopped, use the mechanical brake.
A max. 360 Hz can be selected on the SJ100 Series. However, a two-pole motor can attain up to approx. 21,600
rpm, which is extremely dangerous. Therefore, carefully make selection and settings by checking the mechanical
strength of the motor and connected machines. Consult the motor manufacturer when it is necessary to drive a
standard (general-purpose) motor at over 60 Hz. A full line of high-speed motors is available from Hitachi.
[Installation location and operating environment]
Avoid installation in areas of high temperature, excessive humidity, or where moisture can easily collect, as well as areas that are dusty, subject to corrosive
gasses, mist of liquid for grinding, or salt. Install the inverter away from direct sunlight in a well-ventilated room that is free of vibration. The inverter can be
operated in the ambient temperature range from -10 to 50
!
C
.(carrier frequency and output current must be reduced in the range of 40 to 50
!
C
)
[Application to special motors]
17
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