I-DRIVE TECHNICAL MANUAL – INSTALLATION PG DRIVES TECHNOLOGY
10.2 Immunity
The i-Drive controller has been stringently tested for susceptibility to electromagnetic radiation over the frequency range 26 MHz
to 1 GHz.
Follow the recommendations in Section 10.1.2 to ensure maximum immunity to electromagnetic radiation.
11 Electro-Static Discharge (E.S.D.)
With electronic control systems being installed in more small electric vehicle applications it is important to understand how to
prevent ESD (Electrostatic Discharge) damaging or disrupting systems.
Electrostatic Discharges occur when a charged body comes into close contact with an electrically conductive surface. In the
case of a vehicle the causes are:
A charged operator touching the control panel or machine.
The machine becoming charged and touching an operator or obstacle.
One part of the machine becoming charged through movement or operation (e.g. cleaning brushes) and a flashover
occurring to another part of the machine or electrical system.
When a discharge occurs the currents flowing can be very high with a very fast rise time. This may cause damage or disruption to
the control system either directly or indirectly via transient coupling effects.
In all cases prevention of the prime cause is better than cure. Although measures can be taken to route ESD away from sensitive
areas or protection components added to the system, subtle changes to the system often make cures unreliable. Different
batches of components, slightly different wiring paths or atmospheric conditions etc. will make the system behave differently.
Designing ESD protection is concerned with the performance of the complete operating system, not the individual components.
Items which are exposed to the outside world must normally be protected against high ESD voltages and currents. ‘Under-bonnet’
is either concerned with preventing charge build up or preventing flashover under ESD transient conditions.
There are various international standards currently under development for this aspect of the system’s performance. The controller
is tested to IEC 61000-4-2.
11.1 Electrical Masses
In most electric vehicle systems there are several large electrically conductive masses. The first is the electrical wiring system itself,
including the control system and battery. The others are any electrically conductive mass around the vehicle. The major one will
be the chassis or other major parts of the structure. However, not only can the chassis on some vehicles be non-conductive
(plastic, GRP) but there are often sub-chassis or large metallic components which are electrically isolated from each other.
Each of these electrically conductive masses may become charged by various means. If the charge voltage becomes
sufficiently high then a flashover to another electrically conductive mass such as the electrical system can occur. The
electrostatic discharge produced by this method can be very large and damaging.
Items such as motor cases are also electrically conductive masses that can charge up and cause flashover.
Flashover can either take the form of intermittent large-scale events or as continuous small discharges depending on the voltage
and charge levels. The latter can be the cause of failure when conducting radiated emissions testing for EMC approvals.
11.2 Prevention of Flashover
Prevention mainly concerns preventing differential charge build up on all the different electrical masses around the vehicle. The
electrically conductive masses comprise the electrical system and any large metallic masses around the vehicle such as the
sub-chassis and large electrical components etc.
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