SolaHD offers a broad range of industrial control solutions
for the most demanding industrial applications. Our prod ucts
exceed NEMA ratings for inrush and regulation to ensure
control systems are powered cor rect ly. Elec tro mag net ic
control com po nents demand inrush cur rents up to 10 times
the trans form er’s nominal rating. While this inrush is occur-
ring, the output side of the transformer must not fall below
85% of nom i nal as specifi ed by NEMA ST-1, Part 4. Using
a transformer that does not meet these ratings may cause
erroneous shut downs of down stream pro cess es.
To meet your complete control needs, SolaHD four series
of control transformers, all of which exceed the NEMA
standards. The Se lec tion Chart can be used to identify the
appropriate transformer for your ap pli ca tion.
The SBE series is available from 50 - 5000 VA, 55°C rise
and features copper windings and encapsulation (through
1000 VA) for longer life and pro tec tion from the en vi ron ment.
This low tem per a ture per for mance can mean smaller cabinet
size or longer life for any electronic components that may
be nearby.
The SMT series are 115°C rise, aluminum wound and for
applications where good voltage reg u la tion and higher
power capacities (1000-5000 VA) are required.
The International series meets IEC re quire ments and IP20
(touch proof covers ordered separately for E models) for
Eu ro pe an applications.
The HSZ series rounds out SolaHD’s line with an enclosed
series of control transformers from 1 - 10 KVA that feature
either an UL-3R, NEMA 4X or NEMA 4/12 enclosure.
This unique design, featuring copper windings and
en cap su lat ed construction, can help system de sign ers
meet harsher en vi ron men tal standards or design for a safer
installation outside of a control cabinet. The HSZ series is for
ap pli ca tions where cost or heat issues make mount ing the
trans form er out side the control panel nec es sary.
SolaHD is pleased to offer custom transformers 1 KVA
and larger. If you can't fi nd what you are looking for here, we
are happy to provide a quote on a custom transformer if
available. Contact Technical Services for more information.
Design Choices
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Industrial Control Transformers
contact Technical Services at (800) 377-4384 with any ques tions.
Visit our website at www.solaheviduty.com or
Sizing an Industrial Control Transformer
For proper transformer selection, three characteristics of
the load circuit must be determined in addition to the
minimum voltage required to op er ate the circuit. These
are total steady state (sealed) VA, total inrush VA, and inrush
load power fac tor.
A. Sealed VA - Total steady state sealed VA is the
B. Inrush VA - Total inrush VA is the volt-amperes that the
C. Inrush Load Power Factor is diffi cult to de ter mine without
volt-am peres that the transformer must de liv er to
the load circuit for an ex tend ed period of time.
trans form er must deliver upon initial energization of the
control cir cuit. Energization of electromagnetic devices
takes 30-50 mil li sec onds. During this inrush period the
elec tro mag net ic con trol devices draw many times normal
current – 3-10 times nor mal is typical.
detailed vector analysis of all the load components.
Gen er al ly such an analysis is not feasible, there fore, a
safe assumption is 40% power factor. Until re cent ly
20% PF was com mon ly used for trans form er calculations,
how ev er, tests conducted on major brands of control
devices indicate that 40% PF is a safer default
as sump tion.