Comfortable Driving with Intelligent
Cabin Heaters by BorgWarner BERU Systems
Rapid Heat
Bitter Cold
New Products and Markets
Comfortable Driving with
Intelligent PTC Cabin Heaters
by BorgWarner BERU Systems
By Stephan Weinhold, BorgWarner BERU Systems GmbH, Ludwigsburg
Fuel consumption-optimized engines are very efficient. So efficient, there is hardly enough wasted heat
for heating the vehicles interior. Engine-independent electrical heat sources such as the BorgWarner BERU
Systems PTC (positive temperature coefficient) cabin heaters provide instant window defrost and cozy
compartment warmth ensuring safe and comfortable driving at the start of the engine.
From the compact mechanical design to
electronically regulated comfort, BERU
Systems offers a heater range that can
be flexibly adapted to customer requirements and specifications ranging in output from 500 to 5,000 watt.
Core elements of design are the ceramic
PTC components, which have very low
electrical resistance at low temperatures (when heat is required the most).
Low resistance entails high current
flow and thus high performance, 100%
of which will be transformed into heat.
When temperature increases, the effect
reverses resulting in less heat released.
The graph (Fig. 2) shows the “Working area” and the critical temperature,
a point where higher temperatures are
not possible. This is the basic safety feature (self protection), which functions
even in the event of a software, hardware, or any other type of system fault.
The PTC components are equipped with
an electrically conductive coating. They
are positioned on a contact line in order
to supply the voltage. Aluminum-oxide
foil is placed below the contact pad to
ensure insulation against the housing
(close tube). A plastic frame keeps the
stones in the correct position for the
pressing process within the aluminum
tube. A closed construction design eliminates failure modes possibilities such
as humidity corrosion, which insures
robust world class reliability.
Lamellae are pushed over the heating
rods in order to ensure the necessary
mechanical stability and also for providing sufficient heat transfer surface with
little pressure loss.
This structure forms the basis for our
flexibly packaged high performance
safe heaters, which have shown fantas-
PTC Heater
External Switches
Electronic Control
PWM
communication
LIN
communication
CAN
communication
Figure 1: BERU systems offers mechanically and electronically regulated heating systems. Control
of the electronically regulated systems is either performed via PWM signals or via established bus
systems such as CAN or LIN.
tic potential in the small vehicle segment
having the option of selecting an activation design of one, two, or three heating rods, e.g. via external relays and with
integrated electronics.
Diverse application
possibilities
The PTC cabin heaters by BERU Systems are usually integrated centrally
in the air conditioning unit, mostly directly behind the water heat exchanger. The heated air is moved from there
via channels directly into the interior in
order to heat it up quickly. Sometimes
the heating elements are positioned
peripherally in the area of the outlet
nozzles. This provides the advantage
of smaller heating element dimensions and easier air channel positioning. Even independent modules with
heating element plus a separate fan
are possible.
In addition to these heating systems
for efficiency optimized combustion
engines, BERU Systems also develops
very high-performing PTC heating systems for electric automobiles as these
are supplied with even less waste heat.
In this case, the heating elements must
provide nearly the entire heating supply
but may use only at the exact amount of
required electrical energy in respect to
battery performance.
BERU Systems covers the various requirements with a comprehensive
product range. The basis is formed by
devices with multiple heating levels and
performances, which are controlled via
relay in an external switch box. Three
level heaters with 1,000 watt performance are standard; the established
10000
Lg resistance [Ω]
1000
working area
100
10
Bitter Cold
1
0,1
0
50
100
150
PTC stone temperature [°C]
higher temp. is
not possible
Rapid Heat
Figure 2: PTC characteristic curve with a depiction of the temperature safety limitation. The optimal operation range spans from 120 to 160 degrees Celsius (248 to 320 degrees Fahrenheit). A
higher temperature beyond this range is not possible: Physical limits developed for system safety.
6.3 x 0.8 mm flat plug is commonly used
for connection.
The main feature of heaters with integrated electronics is the variable heatoutput control. The individual heating
rods are individually supplied by power
transistors while the load currents are
linearly regulated up and down in order to avoid peak loads in the on-board
power network. A closed-loop circuit allows the steady adaptation of the heating performance to the requirements of
the climate system. The on-board electronics therefore supply the heater electronics with a pulse width modulated
(PWM) signal. Depending on this signal,
the electronics report a certain current
value to the climate system. This compares the current value with the heating
output requested from the passengers
and readjusts the PWM signal accordingly. This intelligent feedback provides
exact temperatures with minimized energy requirements.
The heaters also feature multiple internal diagnosis functions – such as the
temperature monitoring of the PCB and
automatic deactivation during over- or
undercurrent. In addition, temperature,
voltage and current of the power semiconductors are monitored.
Control is performed either via PWM
signals or via established bus systems
such as CAN or LIN. The integrated intelligence minimizes fluctuations in the
on-board power network and monitors
battery voltage, currents, power transistors and heating rods. These and additional diagnosis data on the EEPROM
can be externally accessed. Various
heater parameters can also be changed
and stored there.
High future potential
The minimum waste heat on electric
and hybrid vehicles provides the heaters with a key role in defrosting fogged
Closed Tube
PTC Stone
Frame
Contact Pad
Isolation
www.beru.borgwarner.com
Connecting Contact
feel good about driving
Figure 3: The PTC components are equipped with an electrically conductive coating and are assembled into an enclosed aluminum tube with contact pad and insulation. The closed construction
design insures robust world class reliability.
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and iced screens and heating the interior cabin. BERU developed special high
performance ceramic registers in cooperation with a German OEM that is
already on the street on this electric compact car.
ter heat exchange in the
electric vehicle suf fices
for providing comfortable
warmth in the cabin interior.
Thus BERU systems provides
its customers with a product that
is applicable in electric or hybrid vehicles without further adaption to the
air conditioning unit.
For this task, they were equipped
with 5,000 watt heating power and
connected to the 400 volt high voltage on-board power network. Thus
the new products are also suitable for
hybrid vehicles with various on-board
voltages.
Redundant high voltage safety is required and implemented in regards to
both mechanics and electronics. An additional contact line is integrated into
the closed tube on the other side of the
PTC component, which in turn is separated from the housing by insulation ceramic. The result is a high voltage circuit
independent from the housing that accommodates the components.
The high voltage load circuit is galvanically separated on the electronics from
the low voltage control circuit. Redundant current measurements (hardware
Printed in Germany · 2,5.10.11 · Bestell-Nr. 5 000 001 097
Chain-Driven Alternator/
Starter Module
Dualtronic™ Control Modules
Dualtronic™ eAssist DCT
eGearDrive® Transmissions
Electronic Coolant Valves
Electric Cabin Heaters
Hybrid Coolant Pumps
Hybrid Fan Drives
Thermal Management Systems
Tire Pressure Monitoring Systems
Turbochargers
In contrast to other possible heating
sources in the electric vehicle, no special
heating circuits or coolants are required.
The technology is based on more than
ten years BERU Systems experience in
series production, in regards to both
heat production and control electronics.
Figure 4: The main feature of the heaters with
integrated electronics is the variable heatoutput control. The individual heating rods are
individually supplied by power transistors while
the load currents are linearly regulated up and
down in order to avoid peak loads in the onboard power network.
and software) and over voltage detection ensure additional safety.
Normally, the installation space available due to the elimination of the wa-
The BERU Systems electric air heaters
contribute to electric mobility, CO2 reduction, and emission reduction. Efficiency is nearly 100%.
Downsizing and/or electrification of
the Drivetrain while sustaining vehicle
cabin heat equal to or exceeding current
levels of customer expectation… BorgWarner BERU Systems, with its highly
modern portfolio of PTC heaters, is well
equipped for these challenges.
n
Driving toward a greener future.
When it comes to developing products for hybrid and
electric vehicles, BorgWarner is creating advanced engine
and drivetrain solutions that reduce emissions and
increase fuel economy while improving performance.
We’re hard at work putting more “go” in going green.
www.borgwarner.com
Greener Future AZ_178x137 E.indd 1
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