Introduction - BMR SFU-0302-SSE Manual

SFU-0302 SSE

1. Introduction

Depending on its construction, the speed of a three-phase a.c. motor is directly dependent on the
number of poles and the frequency of the network. In a 3ph 380V/50Hz network, with a 2-pole
motor, the rated speed would be 50 U/s * 60 = 3000 Upm.
With d.c. motors (brushless d.c.), the speed is dependent on the voltage applied.
Three-phase a.c. motors provide numerous benefits in industry, such as brushless operation,
freedom from wear and tear, favourable capacity/weight ratio, high-speed capability, and much
more. These motors can be used many different application areas, such as milling and grinding
spindles, or with drilling machinery, for example.
D.C. motors have the advantage of a high power efficiency (approx. 85%) when compared with
a.c. motors, but the disadvantage of not quite reaching the torque of an a.c. motor at low speeds
(when starting), nor reaching the high speeds of an a.c. motor. However, the higher efficiency
also means cooling requirements are lower and dimensions can be smaller.
In the aforementioned applications, three-phase a.c. motors are operated using special control
gear – frequency converters. These frequency converters convert the fixed 50 Hz network into a
3-phase network with variable frequency and voltage. This greatly reduces the start-up problems
and the high starting currents that are inevitable when high-capacity three-phase a.c. motors are
connected to a fixed network. The motor is controlled according to a special characteristic curve
until its rated speed has increased, or it has been braked to a standstill.
The frequency converter SFU-0302 -series has been specially designed for use in these high
frequency applications, offering excellent safety, performance and reliability, the result of years of
experience in the design and construction of frequency converters, together with the use of the
latest materials and the most reliable components. It can be used in many different applications
and is as equally suitable for use as a replacement device in existing systems with older type
series as it is in pre-planned applications as a cost-effective solution, helping to prolong the useful
life of tools. In addition, both a.c. and d.c. motors can be operated by this high frequency
converter.
BMR GmbH
M a n u a l
2014-03-17
– 3–
E