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Appendix A
Glossary of Terms & Abbreviations
GLOSSARY OF TERMS
TERM DESCRIPTION OF TERM
Peak force Peak force is the force produced when the peak current is applied to the motor. It is the product of
Force constant (N/A
pk
) and Peak current (A
pk
).
The motor is not moving, there is no forced cooling and no additional heat-sinking. The duration of
the peak force is thermally limited and is therefore only allowable for a period of 1 second.
Continuous stall
force
Continuous stall force is the force produced when the continuous current is applied to the motor.
It is the product : Force constant (N/A
pk
) x Continuous stall current (A
pk
)
or : Force constant (N/A
rms
) x Continuous stall current (A
rms
).
The motor is not moving and there is no forced cooling.
It is quoted with and without the addition of a 25 x 25 x 2.5 cm heatsink plate mounted with
thermal grease to the mounting surface of the motor.
Peak current Peak current is the current required to heat the motor phases to their maximum operating
temperature when the ambient temperature is 25°C, the motor is not moving, there is no forced
cooling and no additional heat-sinking.
It is the maximum allowable current before demagnetisation of the magnets occurs when the
magnet temperature is 100°C.
The duration of the peak current is thermally limited and is therefore only allowable for a period of
1 second.
Continuous stall
current
Continuous stall current is the current required to heat the motor phases to their maximum
operating temperature when the ambient temperature is 25°C, the motor is not moving and there
is no forced cooling.
It is quoted with and without the addition of a 25 x 25 x 2.5 cm heatsink plate mounted with
thermal grease to the mounting surface of the motor.
Force constant Force constant is the peak force produced when 1 ampere (peak) flows into one phase and 0.5
ampere (peak) flows out of the remaining two phases (as in sinusoidal commutation) quoted in
N/A
pk
. Alternatively, it is the peak force produced when 0.707 ampere (rms) flows into one phase
and 0.353 ampere (rms) flows out of the remaining two phases (again as in sinusoidal
commutation) quoted in N/Arms.
Back EMF Back EMF constant is the peak phase to phase voltage generated when the motor is travelling at
a velocity of 1m/s.
Fundamental
motor constant
Fundamental motor constant is the continuous stall force divided by the square root of the power
dissipated in the motor at that continuous stall force.
Eddy current loss Eddy current loss is the amount of opposing force produced by the motor when it is travelling at a
velocity of 1m/s.
Sleeve clogging
force
Sleeve clogging force is the amount of force variation produced by having an iron sleeve. The
variation is independant of motor current.
Resistance Resistance is measured phase to phase at temperatures of 25°C and 100°C.
Inductance Inductance is measured phase to phase at a frequency of 1 kHz. The actual value of inductance
varies as the motor position varies so it is the minimum value that is quoted.
Page 15
ServoTube 38 Installation Guide Appendices