System Design Parameters; Determination Of Nominal Motor Size; Variables - Danfoss MP1 Service Manual

Service Manual
MP1 Motor

System Design Parameters

Determination of Nominal Motor Size

© Danfoss | November 2020
The following equations are used to compute the input flow, output torque, output power and speed.
Generally, sizing the right motor starts with an evaluation of the machine requirements such as speed
and torque. Select a motor that will transmit the required torque, then select a pump that will meet the
flow and pressure requirements of the motor.
Unit: Metric System:
Q =
e
1000 • η
V
g
Output torque M =
e
Q
e
Output power P =
e
Q
e
Speed n =

Variables

SI units [US units]
Q = Input flow l/min (US gal/min)
e
M = Output torque N•m (lbf•in)
e
p = Output power kW (hp)
e
n = Speed min-1 (rpm)
V = Displacement per revolution cm
g
p = Outlet pressure bar [psi]
O
p = Inlet pressure bar [psi]
i
∆p = p - p (system pressure) bar [psi]
O i
η = Volumetric efficiency
v
η = Mechanical-hydraulic efficiency
mh
η = Motor total efficiency (η
t v
Inch System
V • n
g
l/min Q
v
• ∆p • η
m
Nm M
20 • π
• ∆p • η
t
kW P
600
• 1000 • η
v
min n =
-1
V
g
3 3
/rev [in /rev]
• η )
mf
V • n
g
= [gpm]
e
231 • η
v
V • ∆p • η
g m
= [lbf•in]
e
2 • π
V • n • ∆ p • η
g t
= [hp]
e
396 000
Q • 231 • η
e v
(rpm)
V
g
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