For Correct Operation; Application To Motors; Notes On Use - Hitachi SJ300 Series Manual

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
[Application to special motors]
Gear motor
Brake-equipped motor
Pole-change motor
Submersible motor
Explosion-proof motor
Synchronous (MS) motor
High-speed (HFM) motor
Single-phase motor
[Application to the 400V-class 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.

Notes on Use

[Drive]
Run/Stop
Emergency motor stop
High-frequency run
[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℃.(Carrier frequency and output current must be reduced in the range of 40 to 50℃.)
The overspeed endurance of a general-purpose motor is 120% of the rated speed for 2 minutes (JIS C4,004). For operation
at higher than 60Hz, 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 using commer-
cial 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 quickly at lower speeds. Consequently, the continuous torque level (out-
put) will decrease at lower motor speeds. Carefully check the torque characteristics vs speed range requirements.
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
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.)
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.), 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. Also see: Application to the 400V-class 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 motor. The inverter should be used in combination
with a pressure-proof explosion-proof type of motor.
*Explosion-proof verification is not available for SJ300 Series.
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 proper inverter selection, consult the manufacturer.
A single-phase motor is not suitable for variable-speed operation by an 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 the 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 of a mechanical brake should be considered.
A max. 400Hz can be selected on the SJ300 Series. However, a two-pole motor can attain up to approx. 24,000 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 above 60 Hz. A full line of high-speed motors is available from Hitachi.
,
s ability to withstand the centrifugal force generated.
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