Precautions Concerning Use Of Specialized Motors; Notes On The Power Transmission Mechanism - YASKAWA CR700 Technical Manual

2.25 Motor Application Precautions
Audible Noise
■
The audible noise of the motor changes when the carrier frequency setting changes. When you use a high carrier
frequency, audible noise from the motor is equivalent to the motor noise generated when you operate from line
power. If you operate at speeds that are more than the rated rotation speed, the unwanted motor noise increases.

Precautions Concerning Use of Specialized Motors

◆
Pole Change Motor
■
The rated current of pole change motors differs from that of standard motors. Check the maximum current of the
motor before selecting a drive. Always stop the motor before switching between the number of motor poles. If the
number of poles is changed while the motor is turning, the motor will coast to stop due to overvoltage from
regeneration or the overcurrent protection circuitry.
Explosion-Proof Motors
■
To use an explosion-proof motor, you must do an explosion-proof test with the drive. The same is true even for
existing installations of explosion-proof motors. The drive is not designed for explosion-proof areas. Ensure that
the drive is installed in a safe location.
The encoder used with pressure-resistant explosion-proof motors is intrinsically safe. When wiring between the
drive and encoder, always connect through a specialized pulse coupler.
Geared Motors
■
The continuous speed range differs depending on the lubricating method and the manufacturer. In particular, in the
case of oil lubrication, continuous operation in the low speed range may cause burnout. Consult with the
manufacturer for the applications that require frequencies in excess of the rated frequency.
Single-Phase Motors
■
Variable speed drives are not designed to operate with single phase motors. Using capacitors to start the motor
causes a high frequency current to flow to the capacitors and can damage the capacitors. A split-phase start or a
repulsion start can burn out the starter coils because the internal centrifugal switch is not activated. The drive is
for use with three-phase motors only.
Motor with Brake
■
When using a drive to operate a motor with brake, and the brake is connected to the output side of the drive, it
may not release at start due to low voltage levels. Use a motor with brake that has an independent source of power
for the brake. Connect the brake power supply to the power supply side of the drive. Note that motors with built-
in brakes tend to generate a fair amount of noise when running at low speeds.

Notes on the Power Transmission Mechanism

◆
For power transmission machinery that uses oil to lubricate gearboxes, transmissions, or reduction gears, make
sure that you use precaution if you operate the machinery continuously at low speed. Oil does not lubricate the
system as well at low speeds. If you operate at frequencies higher than the rated frequency, it can cause problems
with the power transmission mechanism. These problems include audible noise, decreased service life, and
decreased durability.
136
YASKAWA SIEPC71061723A YASKAWA AC Drive CR700 Technical Manual