SIEB & MEYER SD2B, Описание аппаратуры

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Motor voltage
The motor voltage is the voltage directly available at the motor. The value of the motor
voltage depends on the used electric components. In case of a three-phase power
supply with power choke, controlled drive amplifier and a motor choke, voltage drops of
approx. 4 %, 8 % and 1 % of the mains voltage will result. Additional voltage losses of
approx. 2 % can be observed in a soft net.
Example
The following example uses a controlled drive amplifier with a mains choke at a mains
voltage of 400 V. The following motor voltage will result:
U
Motor
= 400 V − (400 V * 12 %) = 352 V
Voltage constant
Due to its inductance the motor generates a countervoltage which is opposite to the
supplied voltage. This voltage is proportional to the speed and defined in 'volt per
1000 revolutions'. Generally, the values are RMS values measured between the
connection pins.
Example
▶ DC link voltage: 325 V
▶ e.m.f.: 1000 mV/min
A voltage of only 225 V is available to control the motor at 1000 rpm. The theoretical
max. speed of the motor is 3250 rpm. At this speed no torque will be available
anymore, since no current can be applied anymore.
Torque constant
The torque constant specifies the relation between the motor current and the motor
torque (Nm/A). The torque constant results from the required max. speed, dynamic
characteristics, efficiency and the quality of the magnetic material.
Inductive winding resistance
The inductive winding resistance (ωL) is the result of the individual number of windings
of the total winding. During period of downtimes the resistance is zero. It increases with
the frequency.
Ohmic winding resistance
The ohmic winding resistance R is the results from the length and the thickness of
wire. During periods of downtimes it specifies the winding resistance alone.
Electric time constant
The elctric time constant is the quotient of the inductive and ohmic resistance (τ = L/R).
Motors for tightening systems
Generally, motors for tightening systems are high-dynamic motors characterized by
high maximum speeds, high peak torque values, low inertia of masses and small rated
torque values. This results in a small voltage constant, small inductance values, thin
windings and low rotor diameters. Due to the low inductance value motors in tightening
systems are operated at a high pulse with modulation frequency (PWM frequency
16 kHz) to keep the current ripple as small as possible.
W
Electric Performance Dimensioning
Drive Amplifier SD2B / SD2B plus - Hardware Description 73
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