Minebea Motor Manufacturing Corporation
eMINEBEA.COM
Selection of PM Motors
Selection of PM Motors
These motors offer high precision at a low price and are
used in a wide array of office automation equipment as well
as various other applications. Our PM motor offering spans
a large range of motor sizes or output torques. We pride
ourselves on our design and manufacturing systems that
ensure the rapid delivery of motors perfectly suited to their
applications. On this page we list several parameters that
can be used in the selection of a PM motor.
Depending on the application, the conditions of use, and the model in which the motor will be used, it is
necessary to set motor characteristics for optimum conditions. We therefore recommend, in addition to
making a selection based on information on this website, that you order a variety of samples and conduct
an evaluation of the products when in use in the actual equipment. Please contact your local sales
representative or e-mail us for sample order.
Index
1) Selection in view of Torque Requirements (1)
. . . . . . . 2
2) Selection in view of Torque Requirements (2)
. . . . . . . 3
3) Setting of Resistance Value
4) Condition of Temperature
5) Selection of Magnet (1)
6) Selection of Magnet (2)
7) Choice of Coil Extension Method
8) Selection of Gear, Pulley etc.
9) Choice of Combination of Standard Parts
10) Description of Standard Dimensions (1)
11) Description of Standard Dimensions (2)
12) Drive Circuitry and Wiring Diagram
.......4
.......5
.......6
.......7
.......8
.......9
. . . . . . . 10
. . . . . . . 11
. . . . . . . 12
. . . . . . . 13,14,15
These pages do not constitute any part of the product specifications and are intended only as
reference material in aiding with the selection of a motor. Also, please note that the contents of
these page are liable to change without notice. Even if there are any changes to the
information given here, this will have no influence whatsoever on products for which
specifications have already been agreed and which are in production. If there should be any
impact on products already manufactured, we will submit a request for approval of changes to
the customer, and make any such changes only after receiving the customer's agreement.
Page 1 / 15
Copyright 2002 - 2010, Minebea Co., Ltd.
Selection of PM Motors
Minebea Motor Manufacturing Corporation
eMINEBEA.COM
Selection in view of Torque Requirements (1)
The torque generated by a motor is determined by the size of the motor. Also, the heat resistance
temperature of the magnet wires used in the motor limits the maximum torque for each motor size. UL and
other safety standards impose further limitations. These specify that the motor surface should normally be
at 105°C. In addition, when UEW (polyurethane wire: class E) is used the magnet wire heat resistance
temperature is a maximum 120°C. We cannot guarantee reliability if the coil is used at temperatures
exceeding this.
Torque Range According to Motor Size
[x10
-4
N.m]
100
PM10S
PM15S
PM20S
PM20L
PM25S
PM25L
PM35S
PM35L
PM42S
PM42M
PM42L
PM55L
200
300 400
500
600
700
800
900 1000 1100 1200
The above graph shows output torque range by motor size. Within this range, coil resistance and magnet
materials can be tailored for optimum motor settings. For Nd-Fe-B bonded magnets only, it is possible to
control magnetization, and it is therefore possible to make adjustments to rotor flux.
Page 2 / 15
Copyright 2002 - 2010, Minebea Co., Ltd.
Selection of PM Motors
Minebea Motor Manufacturing Corporation
eMINEBEA.COM
Selection in view of Torque Requirements (2)
The output torque of a motor varies according to the drive speed. Even if the motor is driven at the same
voltage, the rise in revolution speed leads to increased occurrence of electrical motive force, and to higher
coil impedance. This in turn makes it harder for current to flow through the coil, thus lowering torque. The
following graphs list the average torque for each size of motor. Please refer to this information in making
your selection.
PM10S
200
~
PM25L
150
Torque [X10
-4
N.m]
100
10S
15S
20S
20L
25S
25L
50
0
0
200
400
600
800
1000
1200
Frequency [Hz]
Magnets for sizes PM15 to PM25 mainly display MS70 characteristics.
PM35
1400
1200
~
PM55
Torque [X10
-4
N.m]
1000
800
600
400
200
0
0
200
400
600
800
1000
1200
1400
1600
35S
35L
42S
42M
42L
55L
Frequency [Hz]
Magnets for sizes PM35 to PM42 mainly display MS50 characteristics,
While magnets for size PM55 display MSPL characteristics.
Page 3 / 15
Copyright 2002 - 2010, Minebea Co., Ltd.
Selection of PM Motors
Minebea Motor Manufacturing Corporation
eMINEBEA.COM
Setting of Resistance Value
Resistance value is restricted by service voltage and rise in motor temperature. Further, there are limitations
on potential settings due to considerations of power conservation and restrictions on power supplies and
motor drivers receiving power. Please pay due attention to these limitations when deciding settings. In
addition, coil winding volume is restricted by motor size, so please refer to the following resistance value
ranges when establishing settings. If priority is placed on torque, after taking temperature rise into account
we can establish settings here by ourselves. In this case, please inform us of the drive conditions, the level
of duty, the method of attachment, temperature conditions during use, and any or all other necessary
specifications.
Resistance Value Range According to Motor Size
100
PM10S
PM15S
PM20S
PM20L
PM25S
PM25L
PM35S
PM35L
4.0Ω MIN
4.0Ω MIN
2.4
ΩMIN
3.0ΩMIN
2.5
ΩMIN
4.0
Ω
MIN
2.2
Ω
MIN
3.0
Ω
MIN
200
300
400
500
600
700
800
900
1000 1100 1200
60Ω MAX
137Ω MAX
190Ω MAX
300Ω MAX
200Ω MAX
500Ω MAX
745Ω MAX
800Ω MAX
800Ω MAX
1000Ω MAX
1000Ω MAX
1000Ω MAX
PM42S 1.6
ΩMIN
PM42M 2.2
Ω
MIN
PM42L 2.4
Ω
MIN
PM55L
3.9Ω MIN
Page 4 / 15
Copyright 2002 - 2010, Minebea Co., Ltd.
Selection of PM Motors
Minebea Motor Manufacturing Corporation
eMINEBEA.COM
Condition of Temperature
The major factor limiting output torque is the temperature of the motor coil. It is therefore necessary to gain
an understanding of the temperature characteristics of the motor under conditions of normal usage. Also,
the surface area varies according to motor size, and radiation characteristics therefore also naturally vary,
leading to changes in motor temperature. The following shows the major characteristics of our motors.
Please pay particular attention to this information when selecting a motor.
Coil temperature rise per 1W input
PM15S
54
PM20S
35
PM20L
31
PM25S
30
PM25L
26
PM35S
19
PM35L
16
PM42S
15
PM42M
14
PM42L
13
PM55L
8
* If input power (W) is multiplied by the relevant value above, you can gain a rough estimate of the coil temperature.
Ratio between motor surface temperature and coil temperature
PM15S
0.9
PM20S
0.91
PM20L
0.91
PM25S
0.91
PM25L
0.91
PM35S
0.88
PM35L
0.87
PM42S
0.87
PM42M
0.88
PM42L
0.88
PM55L
0.87
* If you measure the motor surface temperature and divide that figure by the relevant value above, you can gain a rough estimate of
the coil temperature.
Time to reach coil temperature saturation
120
100
Temperature rise ratao [%]
80
60
40
PM15S
PM20S
PM20L
PM25S
PM25L
PM35S
PM35L
PM42S
PM42M
PM42L
PM55L
The graph shows the amount
of time until the coil reaches
saturation temperature.
This information allows you
to judge when overdrive is
possible for a short time,
such as when the motor is
operating under light duty
conditions of use.
20
0
0
10
20
30
40
50
60
70
80
TIME (MIN)
Page 5 / 15
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