Tech Briefs Magazine - April 2021 - MD-7

and respond by reducing the activation
voltage to a holding voltage, taking the
guesswork out of the determination. By
conveying real-time data about brake disengagement and performance to other
controllers or computers with monitoring software, the smart controller serves
as a diagnostic tool to maintain overall
drive system health. Interchangeable with
existing brake controls and able to be
seamlessly integrated into the Industrial
Internet of Things (IIoT), this innovation
takes spring set/electrically released
brake controls to the next level.

Standard Spring Set Brake Controller - Manual Set Holding Voltage Time
Wasted Time
Safety Factor

Standard Brake Controls
In all spring set brakes, an armature is
biased against the friction elements by a
set of springs between the brake housing
and the armature. The spring force
pushing against the armature squeezes
the brake rotational friction elements
against the stationary friction elements,
thereby stopping the rotational friction
elements, creating torque. The brake is
disengaged by applying DC current to
the brake coil. The coil produces an
electromagnetic field in the brake housing that pulls the armature against the
springs and across a preset air gap
until the armature abuts
the housing. At
this

Manually Set Time

Worn

Holding

New

Voltage

Disengagement

0.25

1.5

0.5
Time Seconds

Figure 1. At any point in the life of the brake, the amount of time beyond the full disengagement before the
voltage is reduced to the holding voltage is shown as Wasted Time.

point, the brake is fully disengaged.
Holding the armature against the housing requires a lower-strength magnetic
field because of the elimination of the
air gap, allowing the activation voltage
to be reduced to a holding voltage.
The manually set lower holding voltage
allows the brake to run cooler, requiring
lower power consumption and causing
less wear of the brake. Generally, the
required holding voltage varies negligibly
with changes in environmental conditions
and does not vary with brake wear.
In standard brakes, the time interval
between the initial activation voltage and
the reduced holding voltage, or brake
disengagement time, is also set manually. Environmental and operating variables that are application specific - such as temperature, vibration, shock
loading, con -

Motion Design, April 2021

tamination, cycle rates, and wear - affect
the brake disengagement time from cycle
to cycle and over the life of the brake. If
the disengagement time is underestimated, the motor engages before the brake is
fully disengaged, causing the two to work
at cross purposes, resulting in increased
wear and excessive heat generation. An
overestimate of disengagement time causes, at a minimum, longer cycle rates and
higher power consumption.
For the best performance and longevity, the user establishes the disengagement
time based on the maximum amount of
time required for disengagement at the
end of the brake's operational life,
accounting for all environmental variations and adding a safety factor. The safety factor assures
that the

Cov

ToC

http://www.abpi.net/ntbpdfclicks/l.php?202104TBNAV

Tech Briefs Magazine - April 2021

Table of Contents for the Digital Edition of Tech Briefs Magazine - April 2021