Electricity + Control February 2019

Comparison of different braking technologies

Symbols and definitions

ac:

Alternating current or voltage

PF:

Power Factor defined as PF = P/S (power/voltampere) = I 2 /I s * DPF (With sinusoidal current PF is equal to DPF)

B:

Friction coefficient

T:

Torque (Newton metre, Nm)

C:

Constant or coefficient

t:

Time

cos ϕ :

Cosine of electrical angle between the fundamental voltage and current

THD:

Total harmonic distortion in the current is defined as

dc:

Direct current or voltage

I ∑ 2 2 40 k

Displacement Power Factor defined as cos ϕ 1 where ϕ 1 is the phase angle between the fundamental frequency current drawn by the equipment and the supply voltage fundamental frequency component.

DPF:

=

THD

I

1

where I 1 is the rms value of the fundamental frequency current. TheTHD in voltage may be calculated in a simi- lar way.

I:

Current [Ampere, A]

U:

Voltage [V]

J:

Inertia [kgm 2 ]

W:

Energy [Joule, J]

n:

Rotation speed [revolutions per minute, rpm]

ω :

P:

Power [Watt, W]

Angular speed [radian/second, 1/s]

This article is taken from ABB Drives: the Technical Guide No. 8: Electrical braking.

Electricity + Control

FEBRUARY 2019