Glossary

Force at high saturation in the magnetic circuit resulting from the ultimate current beyond the saturation point where F ≁ I. The permitted duration for the ultimate force is less than 1 second. The ultimate force should not be used as a dimensioning variable.

Peak force is referred to the saturation range of the motor where F ≁ I. This motor force is generated at peak current I_p. The permitted duration of the peak force depends on the current motor temperature and is typically less than 3 seconds.

Peak motor force which is reached at the end of the linear range of the F/I curve of the motor with F ~ I at I_pl. It results in a noticeable heating.

Motor force at continuous current I_c if all motor phases have the same loads. In order not to exceed the permissible motor temperature, sufficient heat dissipation by convection, conduction and radiation must be ensured.

Displacement force because of friction.

Cogging (ripple force) — the sum of forces arising from reluctance, which work in the feed direction when the motor is moved without current input and cause a force ripple during operation.

A vertical installed linear motor system has to work permanently against the force of gravity because of the weight of the moving parts. The weight compensation force F_Wc is provided by a passive weight compensation unit. F_Wc represents the force which is measured in vertical direction. This force pulls up the moving part because of an overcompensation.

Maximum effective motor current at which the motor achieves its ultimate force. At I_u the coil temperature can increase up to the permitted maximum value in less than 1 second.

Maximum effective peak current in the range of a few seconds (max. 3 s). When the motor is working with I_p, then the coil temperature must not exceed the maximum permitted value.

Maximum effective peak current in the linear range of the motor where F ~ I.

Effective current at related power loss without compulsory cooling option but at sufficient cooling by heat convection, radiation and conduction.

The thermal output resulting in the motor winding which leads to a time-dependent temperature increase subject to the operating mode (current) and the ambient conditions (heat dissipation). It is particularly high in the high dynamic range (F_p) due to the square relationship of current, and relatively low in the I_c range. Calculation formula (at 25°C): P_l = (F / k_m)².

Peak power loss at I_p (at 25°C).

Power loss at I_c (at 25°C).

Motor constant which expresses the relation between the generated force and the power loss (efficiency of the motor). It is dependent on the temperature. k_m is referred to a coil temperature of 25°C.

Winding parameter which, when multiplied by the current in the linear dynamic range, represents the motor force that is being produced: F = I_c · k_f.

Winding parameter which represents the armature countervoltage arising at the motor terminals in generator operation, subject to the speed. Generator voltage: U_g = k_u · v.

Maximum speed at U_DCL. The maximum speed is the limit speed that the motor can achieve. It is referred to F_p at I_p when the motor is working with U_DCL. At movement systems it can be restricted too because of mechanical factors.

The maximum achievable acceleration of a movement system can refer to the peak forces or can be restricted because of mechanical factors.

Winding resistance at 25°C.

Duration until the coil temperature reaches 63% of the coil end temperature when operating with constant power loss.

Motor inductance.

Constant which describes the L/R ratio. The ratio is approximately constant, regardless of the winding system design. The controlled effective time constant decreases with increasing voltage overshoot. At 1 τ_el, the motor will reach approximately 63% of the final force value corresponding to the current command.

The maximum permitted temperature for the windings must not be exceeded. The winding temperature is referred to the measured temperature by a sensor installed in the winding.

DC link voltage or supply voltage of the power actuators. The higher the speed and the countervoltage that rises with it, and the greater the losses in the cables and power electronics, the higher the required DC link voltage.

The magnet period (also pole pair width) 2τ_p denotes the travel distance of a pole pair on the linear motors. At the same time, τ with index p is the pole pitch.

Accuracy, repeat accuracy (also known as repeatability) and resolution are in context.

The positioning accuracy of a motion system refers to maximum deviation respectively closeness of the approached position from the desired position.

The positioning repeat accuracy refers to the distances respectively closeness between positions to each other which are reached when the same target position is approached multiple times.

Resolution of a positioning system is referred to the smallest distance which can be measured by an encoder.