User guide

Page 37
ServoTube 25/38 module User Guide
Appendices
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 forcer. It is the product of Force
constant (N/Apk) and Peak current (Apk).
The forcer 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 forcer.
It is the product : Force constant (N/Apk) x Continuous stall current (Apk)
or : Force constant (N/Arms) x Continuous stall current (Arms).
The forcer 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 forcer.
Peak current Peak current is the current required to heat the forcer phases to their maximum operating temperature
when the ambient temperature is 25°C, the forcer 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 forcer phases to their maximum operating
temperature when the ambient temperature is 25°C, the forcer 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 forcer.
Force constant Force constant is the peak force produced when 1 ampere (peak) ows into one phase and 0.5 ampere
(peak) ows out of the remaining two phases (as in sinusoidal commutation) quoted in N/Apk. Alternatively,
it is the peak force produced when 0.707 ampere (rms) ows into one phase and 0.353 ampere (rms) ows
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 forcer is travelling at a velocity
of 1m/s.
Fundamental forcer
constant
Fundamental forcer constant is the continuous stall force divided by the square root of the power dissipated
in the forcer at that continuous stall force.
Eddy current loss Eddy current loss is the amount of opposing force produced by the forcer when it is travelling at a velocity
of 1m/s.
Sleeve cogging force Sleeve clogging force is the amount of force variation produced by having an iron sleeve. The variation is
independent of forcer 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 forcer position varies so it is the minimum value that is quoted.
Electrical time constant Electrical time constant is the time taken for a step current input to the forcer to reach 63.2% of its value.
Continuous working voltage Continuous working voltage is the maximum allowable continuous voltage between any two forcer phases
or between any forcer phase and the forcer safety earth.
Pole pitch Pole pitch is the distance in millimetres for one complete electrical cycle (between like magnetic poles).