DC Motors
11
Table E Radial Load Capacity
1
1
Data for motors with roller bearings at the drive end (back end). Motors with ball bearings at the drive end are
for coupled duty only.
Deriving Motor Constants
Various motor constants are required to set control functions for stabilized
operation of motor and controls. The following information will make it
possible to derive approximate motor constants from the nameplate data.
Required Nameplate Data
•
Frame
•
HP
•
RPM
•
Volts (Va)
•
Amps (Ia)
From
, the following factors are available, based on frame size.
•
Ra´
•
La´
•
WK
2
• τ
e´
This will provide approximate results with a
±
25% margin of error.
The following data can be derived:
La = La´ x (Va/rpm)
2
Arm. Circ. Ind. (millihenries)
Ra = Ra´ x (Va/rpm)
2
Arm. Circ. Resistance
τ
e
=
τ
e´
τ
e´ = La/Ra x 10
3
Elec.Time Constant
J (SEC) = WK
2
x (rpm)
2
/1.62 x (10)
6
x hp where WK
2
is in terms of lb-ft
2
J (SEC) = WK
2
x (rpm)
2
/0.0922 x (10)
6
x kw where WK
2
is in terms of kg-m
2
R = Ia x Ra/(Va – IaRa)
Table F Resistance & Inductance Factors
Frame
Capacity at End of Shaft in kg (lbs.)
2500 RPM
1750 RPM
1150 RPM
850 RPM
DC210ATZ &
DC180ATZ
140.6 (310)
156.5 (345)
179.2 (395)
200.0 (440)
C180ATZ
226.8 (500)
256.3 (565)
283.5 (625)
283.5 (625)
Frame
WK
2
Ra
La
τ
e
lb.-ft.
2
kg.-m.
2
C1811ATZ
0.683
0.029
56.6
616
0.011
C1812ATZ
0.787
0.033
40.5
500
0.012
