– A-32 –
Panasonic Corporation Electromechanical Control Business Division
industrial.panasonic.com/ac/e/
©
Panasonic Corporation 2018
AQCTB02E 201806-E
– A-33 –
Panasonic Corporation Electromechanical Control Business Division
industrial.panasonic.com/ac/e/
©
Panasonic Corporation 2018
AQCTB02E 201806-E
Terminology
Torque
(N·m)
(kgf·cm)
Speed
(r/min)
(2)
(3)
(1)
(6)
(5)
(4)
• Speed-torque characteristics
(1) Starting torque
(2) Stalling torque
(3) Rated torque
(4) No load speed
(5) Rated speed
(6) Synchronous speed
Rating
There are limits of operation in terms of temperature rise to assure the motor performance. Rating is divided into
continuous rating and short-time rating.
This defines not only the running limit against the output, but also limiting conditions such as voltage, frequency
and rotational speed. These conditions are called as rated voltage, rated frequency and rated speed.
No load speed (see (4) in the figure)
Motor speed with no load applied. In the case of induction and reversible motor, this speed becomes a few
percent lower (approx. 20 to 60 r/min) than a synchronous speed.
Rated rotational speed (see (5) in the figure)
Motor speed at which the motor generates the rated output. This is the most optimum speed.
Overrun
Revolutions that the motor makes from when the power source is turned off till the motor stops, and is described
in the number of revolutions.
Fit tolerance
Fit tolerance symbol (JIS) is applied to dimensions
of motor “Faucet face” and “Gear head” output
shaft. The value of tolerance depends on the basic
dimension. See the table right.
Synchronous speed (see (6) in the figure)
An inherent speed determined by the number of poles of the motor and frequency of the power source.
This is described in the following formula.
where,
Ns
: Synchronous speed
(r/min)
f
: Frequency
(Hz)
P
: Number of poles
120
: Constant
For example of 4-pole motor and power source frequency is 50 Hz, then,
Continuous rating and short-time rating
A time rating is used to express the time during which the motor can normally output the rated power. Continuous
rating indicates that the motor can provide the rated power during this period. The short-time rating indicates that
the motor will reliably operate to produce the rated output for the relatively short time specified.
Rated output
An optimum output performance which the motor can generate at the rated voltage and frequency. A rotational
speed and torque with which the rated output is generated is called the rated speed and torque. In general, an
output is referred to as the rated output.
Starting torque (see (1) in the figure)
A torque which the motor generates at starting. The motor will not start if a larger load than this starting torque is
applied to the motor.
Stalling torque (see (2) in the figure)
A maximum torque which the motor can generate at constant voltage and frequency. The motor will stall if a
larger load than this torque is applied to the motor.
Rated toque (see (3) in the figure)
A torque of the motor generates the rated output continuously at rated voltage and frequency. This is usually
referred to as a torque at the rated speed.
Output
Output represents a work which the motor can carry out in a unit time. This is determined by the rotational speed
and the torque of the motor. The rated output of the motor, P0 is described in wattage
P0 (W)
as;
• SI units
• Gravitational system of units
P0 = 0.1047
x
T
x
N
P0 = 1.027
x
T
x
N
T
: Torque
(N·m)
T
: Torque
(kgf·m)
N
: Rotational speed
(r/min)
N
: Rotational speed
(r/min)
Slippage
Slippage can be described in the following formula as one of the rotational speed.
where,
Ns
: Synchronous speed
(r/min)
N
: Discretionary no load speed
(r/min)
when an induction motor with 4-pole, 50 Hz runs with a slippage, S = 0.1, then,
N = Ns (1
–
S) = 1500 (1
–
0.1) = 1350 (r/min)
Ns = f
(r/min)
120
P
Ns = = 1500 (r/min)
120
x
50
4
S = or N = Ns (1
–
S)
Ns
–
N
Ns
Shaft tolerance (unit: mm)
Shaft tolerance class: h7
0
–0.01
0
–0.012
0
–0.015
0
–0.018
0
–0.021
0
–0.025
0
–0.03
0
–0.035
Classification of standard dimension
Equal to or below
3
6
10
18
30
50
80
120
Over
–
3
6
10
18
30
50
80
motor
