Page 27 - EE Times Europe November 2021 final

EE|Times EUROPE 27

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

1. DC breaker, contactor, and/or switch
disconnector
2. CMS battery monitoring
3. Main DC breaker, contactor, and/or
switch disconnector
4. DC SPD
5. Power supply monitoring relay
6. AC main breaker and RCD
7. AC contactor
8. Insulation monitor

Figure 2: Exploded view of energy storage

transformer is UL-listed, which provides voltage while providing the necessary match- need to be rated to a different category.
assurance of design safety. ing and common-mode noise removal so that These categories determine the level of
As Figure 4 shows, this 1,500-V signal the communications between the monitoring surge testing that is required during qual-
transformer isolates and protects the battery ICs and the central management board are ification. Surge tests are used primarily to
management system (BMS) board isoSPI™ also secure and uninterrupted. In addition, check that there is adequate clearance so that
interface. It is important to note that the BMS the features of the Model SM91527L trans- if an event such as a lightning strike were
interface is operating in a non-hazardous former allow it to still meet isoSPI™ driver to occur, the gap between the windings on
environment separate from the battery pack recommendations in terms of insertion loss the transformer would not break down and
(max 1.2 dB at 4 MHz) and EMI (–50-dB, ionize, causing a crossover. To be rated at
1- to 100-MHz CMRR). 1,500 V for an overvoltage Category II up to
a 5,000-meter altitude, the reinforced trans-
INSULATION REQUIREMENTS FOR former must be able to withstand an impulse
TRANSFORMERS RATED TO 1,500 V test of 12 kV peak.
Transformers with reinforced insulation up to Another series of tests are mandatory for
1,500 V must pass tests as defined by checking the quality of the insulation mate-
IEC 60664 to demonstrate that the insulation rial itself. Reinforced insulation is checked by
will survive sudden surges, which could hap- applying a DC or AC voltage between the pri-
pen on the electricity grid or on the battery mary and secondary side and measuring the
pack itself. One of the factors to consider is amount of leakage current between the two
the type of application. Consumer equipment sides. This is also known as a dielectric test,
will have a particular overvoltage category as the permittivity of the insulation material
Figure 3: Model SM91527L requirement, while industrial equipment may will accumulate charge, which translates into

Figure 4: Block diagram showing the connection of the isoSPI™ bus between master and slave

www.eetimes.eu | NOVEMBER 2021