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28 EE|Times EUROPE

Magnetics Components That Match 1,500-V Battery Energy Storage System Requirements

Figure 5: Block diagram of elements in a high-voltage battery system

a leakage current. Another name for this test in the middle of a daisy chain. Hi-POT and As the use of renewable
is Hi-POT. impulse tests are still required, but the pro- energy systems expands,
In addition to the Hi-POT test, there is cedure is less severe (4.3-kVDC Hi-POT and
another procedure required in systems with 8-kV impulse). 1,500-V battery packs and
working voltages higher than 750 VDC. This Figure 5 illustrates where the reinforced
procedure puts the transformer through an single-channel transformer and functional inverters will need a growing
aging process using high temperature and two-channel transformer would be located supply of components also
humidity. To test aging, the evaluation consists in a 1,500-V BESS. The BESS is divided into
of ramping up the DC voltage from zero to a strings of 50-V battery modules in which rated to 1,500 V.
value dependent on the working voltage while each is monitored and each has a two-
at the same time measuring in coulombs the channel transformer in the isoSPI™ inter-
amount of charge gathered in the insulation. face. This configuration enables the string to SM91501ALO from Bourns is also UL-listed
This test is also known as partial discharge. be protected with the reinforced and is a two-channel transformer rated to
Bourns performs partial discharge testing as a single-channel magnetic component. 1,500 VDC (functional insulation), which
normal procedure in its manufacturing process can be used in battery module enclosures
for reinforced transformers, such as for its COMPONENTS FOR INCREASED 1,500-V inaccessible to human contact. Because both
Model SM91527L signal transformer. BATTERY STORAGE EFFICIENCY transformers are UL-listed, they provide an
It has become a requirement to use This article has provided a viable reinforced assured level of design safety.
transformers with reinforced insulation at insulation solution for isoSPI™ buses in As the industry for renewable energy
the point of entry into networks, especially renewable energy systems working at 1,500 V. systems expands, 1,500-V battery packs
if the battery management board could be Helping meet higher battery energy stor- and inverters will need a growing supply of
exposed, to enable testing and diagnostics by age efficiency needs, the Bourns® Model components also rated to 1,500 V. Bourns is
a technician. However, if the racks that hold SM91527L is a UL-listed signal transformer committed to continued innovation in the
battery modules are shielded by plastic walls with common-mode choke. This single- development of magnetics components to
and use transformers for communication in channel device is designed for entry points address these needs. ■
a daisy-chain configuration, they will not into strings of battery modules. The signal
require reinforced insulation. In that case, performance of the Model SM91527L has been REFERENCE
transformers with functional insulation for tested to meet recommendations by IC manu- 1 Wood MacKenzie, “U.S. Energy Storage Monitor
1,500 V can be used, such as the Bourns® facturers for operation with their drivers. The Report,” July 2021
Model SM91501ALO transformer, which is Bourns® transformer matches strict specifica-
also UL-listed. This device has two channels tions in terms of surge voltage and other tests isoSPI is a trademark of Linear Technology
instead of one and is suited for placement for its solid insulation. In addition, the Model Corporation.

NOVEMBER 2021 | www.eetimes.eu