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Applicable to standard motors
Driving a 230V , 3 phase standard motor
When driving a 230V standard motor with an inverter,
damage may occur in the insulation of the motor. Use the
output circuit filter (OFL) if necessary after confirmation
with the motor manufacturer.
Torque characteristics and temperature rise
When the inverter is used to operate a standard motor, the
temperature rises a little higher than during operation by a
commercial power supply. The cooling effect decreases in
the low-speed range, reducing the allowable output torque.
(If a constant torque is required in the low-speed range,
use an inverter motor or a motor fitted with a separately
excited fan.)
Vibration
Use of an inverter does not increase vibration of a standard
motor, but when the motor is mounted to a machine,
resonance may be caused by the natural frequencies
including the natural frequency of the machine system.
• IMO recommend that you use rubber coupling or anti-
vibration rubber, where possible
1
.
• We also recommend that you use the inverter skip
frequency control function to avoid resonance point in the
motor operation.
Note that operation of a 2-pole motor at 60Hz or over may
cause abnormal vibration.
Audible noise
When an inverter drives a standard motor, the motor noise
level increases compared with driven by a commercial
power supply. To reduce noise, set the inverter carrier
frequency at a high level
1
. High-speed operation at 60Hz or
over can result in more noise.
Installation location
Use the inverter in an ambient temperature range between
-10 to 50˚C.
• When driving an inverter of 22kW or smaller at a place in
a temperature of 40˚C or over, remove the ventilation
covers. Install an inverter on non-flammable material. The
inverter and braking resistor surfaces become hot under
certain operating conditions.
Applicable to special motors
Explosion-proof motors
When driving an explosion-proof motor with an inverter,
use a combination of a motor and an inverter that has been
approved in advance. Such approved products are available
in our special product series. Contact IMO for details.
Submersible motors and pumps
These motors have a larger rated current than standard
motors. Select the inverter capacity so that these motors
can run within the inverter rated current. These motors
differ from standard motors in thermal characteristics. Set
a small value according to the thermal time constant of
motor for setting electronic thermal relay function.
Brake motors
For motors with parallel-connection brakes, obtain the
brake power from the primary circuit (commercial power
supply). If you connect the brake power to the inverter
power output circuit by mistake, problems may occur. Do
not use inverters for driving motors equipped with series-
connection brakes.
CAUTION
Geared motors
When the power transmission mechanism uses an oil-
lubricated gearbox or speed changer/reducer, continuous
motor operation at low speed may cause poor lubrication.
Synchronous motors
It is necessary to use software suitable for the motor type.
Contact IMO for details.
Single-phase motors
Single-phase motors are not suitable for inverter-driven
variable speed operation. Use three-phase motors.
• Even if a single-phase power supply is available, use a
three-phase motor, because the inverter provides three-
phase output.
Combination with peripheral device
Installing MCCBs
Install an Auto Breaker (MCCB) or earth-leakage circuit
breaker in the primary circuit of the inverter to protect
cables
2
.
Magnetic contactor in the motor circuit
If a magnetic contactor is mounted in the motor circuit for
switching to the commercial power supply or for any other
purposes, ensure that the inverter and the motor are
stopped before you turn on or off the contactor.
Magnetic contactor in the primary circuit
Do not open or close the magnetic contactor in the primary
circuit more than six times an hour. If frequent starts or
stops are required during motor operation, send FWD or
REV signals to the control terminal.
Protecting the motor
When you drive a motor with an inverter, the motor can be
protected with an electronic thermal relay function of the
inverter. In addition to the operation level, set the motor
type (standard motor, inverter motor). For high-speed
motors or water-cooled motors, set a small value as the
thermal time constant and protect the motor in
combination with the "cooling system OFF" signal. When
driving several motors with an inverter, connect a thermal
relay to each motor and turn on the inverter's electronic
thermal relay function. If you connect the motor thermal
relay to the motor with a long cable, high-frequency
current may flow into the wiring floating capacity. This may
cause the relay to trip at a current lower than the set value
for the thermal relay. If this happens, lower the carrier
frequency or use the output circuit filter (OFL) or output
choke.
Power-factor correcting capacitor
Do not mount the power-factor correcting capacitor in the
inverter primary circuit. (Use the DC reactor to improve
the inverter power factor.) Do not use the power-factor
correcting capacitor in the inverter secondary circuit.
Overcurrent trip will occur, disabling motor operation.
Reducing electronic noise (EMI)
Use of filter and shielded wires are typical measures
against noise that meets EMC Directives. For details, refer
to the operation procedure manual.
IMO Precision Controls Limited
1000 North Circular Road
Staples Corner, London NW2 7JP
Telephone: +44 (0)20 8452 6444
Fax: +44 (0)20 8452 3512
Web: www.imopc.com
Email: imo@imopc.com
Measures against surge current
If OU trip occurs while the inverter is stopped or operated
under a light load, it is assumed that the surge current is
generated by open/close of the phase-advancing capacitor
in the power system.
• Connect a DC reactor to the inverter.
Megger test
When checking insulation resistance of the inverter, use a
500V megger and follow the instructions described in the
instruction manual.
Wiring
Control circuit wiring length
When conducting a remote control, limit the wiring length
between the inverter and operator box to 20m or less and
use twisted shielded cable.
Wiring length between inverter and motor
If long wiring is used between the inverter and the motor,
the inverter will overheat or trip because of overcurrent
(under the influence of high-frequency current flowing into
the cable capacitance) in the wires connected to the
phases. Ensure that the wiring is shorter than 50m.
If this length must be exceeded, lower the carrier
frequency or mount an output circuit filter (OFL).
Wiring size
Select a cable with a sufficient capacity by referring to the
current value or recommended wire size given in the
regulations.
Earthing
Securely ground the inverter using the earth terminal.
Inverter Capacity
Driving standard motor
Select an inverter from the capacity range of nominal
applied motors shown in the inverter standard
specifications table. When large starting torque is required
or acceleration or deceleration is required in a short time,
select an inverter with a capacity one class greater than the
standard.
Driving special motor
Select an inverter that meets the following condition:
Inverter rated current > Motor rated current.
Transportation, storage
When transporting or storing inverters, select the
procedures and places that meet the environmental
conditions given in the inverter specifications. Ensure that
the above environmental conditions are met also when
transporting an inverter mounted to a machine.
1
Caution – this may cause EMC problems – check with
IMO first.
2
Can cause nuisance tripping.
If in doubt contact IMO.
Out-of-hours telephone contacts:
Product Support (UK South)
0831 207220
Product Support (UK North)
0836 259108
Product Support (UK Central)
0831 207221
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