The induction motor is
classified into a single-phase motor and a three-phase
motor according to the using power source. This
motor always uses both auxiliary winding and condenser
not only when starting but also during operation.
Generally speaking, its starting torque is not so
great, but its structure is simple and reliable.
In addition, its connection is simple. It is suitable
to use in houses and on factories. For a single-phase
induction motor, be sure that the condenser indicated
in the name plate should comply with the capacity
of the motor.
-
For a single-phase induction motor,
it is not possible to reverse the direction of rotation
within a short time during operation because of
the inertia torque exerting adversely against the
direction the motor is supposed to change to.Thus,
stop the motor first and change the rotational direction
next. In case you do not, the motor can be damaged.
-
The power source of a single-phase
motor includes J (100V 50/60Hz), U(115V 60Hz), L(200V
50/60Hz) C(220V 60Hz, 230V 50/60Hz). Refer to (Fig.
1)
-
The three-phase induction
motor has simpler connection, and higher efficiency
and reliability than the single- phase motor, because
it can be driven by a three-phase power source directly.
The three-phase motor is popular as a general-purpose
motor. The power source for a three-phase motor
includes H (220V 60Hz, 230V 50/60Hz), M (380V 50/60Hz),
Z (440V/460V 50/60Hz). Refer to (Fig. 2)
- It is possible to use the motor for continuous rated
operation.
- It is designed to be used in a single direction.
- The number of rated revolution of the motor varies depending
on the load imposed on it.
- It is suitable for such operation that does not need
the speed control.
- Its insulation class is B. Our UL conformance motor
is class A.
-
Under a constant voltage,
the relationship between the number of rotation
and the torque is as shown in (Fig. 3). With no-load,
the number of rotation roughly approximates the
number of synchronous rotation, but as the load
increases, the number of rotation decreases and
reaches the torque TL The stable zone is to this
point.
-
When the load is further increased
and over the point TM, that is, the torque of the
motor reaches the unstable zone, the motor stops
and restriction electricity runs. As a result, the
motor generates high heat, and then it can be damaged.
Therefore, a safe operation is possible if only
the motor is used within the stable zone of the
load.
-
The characteristic of
voltage can be represented by the torque's characteristic
about the applied voltage. The torque of induction
motor changes in proportion to two times the voltage.
-
The characteristic of torque also
change according to the capacity of the condenser.
-
The characteristic of torque also
change according to the capacity of the condenser.
-
As the capacity of the condenser
boost, the starting torque and stalling torque increase.
But if the capacity is increased by 2.5~3.0 folds,
the operating torque decreases and the starting
torque do not increase.
-
As a simple method to increase the
torque when the induction motor is short on torque,
either the voltage or the
condenser capacity can be increased to continue
the operation. In this case, the loss input of the
motor increases
and the temperature rises rapidly.
-
However, if the motor must be run
with insufficient torque, take measures to let the
motor release heat as much as possible and operate
the motor while keeping the temperature of the motor's
housing
below 90¡É. Refer to (Fig. 4)
GENERAL SPECIFICATION OF INDUCTION MOTORS
Item
Specification
Insulation
Resistance
100M§Ù or more when 500V
megger is applied between the windings and the housing
after rated motor operation under normal ambient
temperature and humidity
Dielectric Strength
Sufficient to withstand
1500V at 50/60Hz applied between the windings
and the case after rated motor operation under
normal ambient temperature and humidity for 1
min.
Temperature Rise
class A (65¡É) or class B (85¡É)or less increase measured
by thermometer after rated operation
Insulation Class
Class B(130¡É), UL approval
motor class A (105¡É)
Overheat Protection
Device
Built-in thermal protector
(automatic return type)
:Open 130¡É¡¾5¡É Close 77¡É¡¾5¡É
Ambient Temperature
-10¡É~+50¡É (with UL,
CE marked motors: -10¡É~40¡É)
