Specifications

Doc Number: VIS-ANA-VER-01001-9002
Date: 27 May 2004
Issue: 5.0
Page: 21 of 80
Author: J. Delgadillo
Controls Preliminary Design Report Issue 5.doc
4.2.4 AZ/ALT Power Drive Unit
Refer to the following representative photograph (Figure 4.2.2.1.A) and block diagram
(Figure 4.2.2.1.B) of the AZ/ALT Power Drive Unit.
4.2.4.1 AZ/ALT PDU Power Feeds
Two power feeds are utilized by the PDU. 230 VAC, 1φ technical power gets routed through
the logic circuit breaker, a single phase EMI filter for attenuation of conducted emissions and
to two universal input switching power supplies. The PDU logic power supply is a 100 W
switching power supply that has multiple outputs for delivering logic power to the various
PWBs and other components in the PDU. The encoder power comes from a 45W power
supply that will deliver power to the 4 Azimuth and 4 Altitude tape encoder read-heads
(AD01 11.1.6 g spec), to the Heidenhain Encoder Splitter boxes (IBV606) and to the
Heidenhain Interpolator boxes (IBV660B). The Heidenhain IBV 606 Encoder Splitter boxes
will be utilized to split the encoder read-head sinusoidal signals. One output will be
dedicated for use by the AZ/ALT PDU. The second sinusoidal output will be routed over to
the AZ and ALT LCUs.
The second power feed comes from the output of the VertexRSI provided isolation
transformer, which is 230 VAC, 3φ, Y-configuration. The power goes through the motor
controller power disconnects and into 6 individual 3-phase EMI filters feeding the Azimuth
and Altitude motor controller power supplies. The motor controller power supplies use the
3φ voltages and convert it to a DC bus voltage that feeds the motor controllers.
4.2.4.2 AZ/ALT PDU Motor Controllers
The motor controllers, configured for Current (Torque) mode, are used to drive the four
Azimuth and the two Altitude Brushless DC motors. For Azimuth, motor resolvers are used
by the motor controllers for sinusoidal commutation (AD01 11.1.4.1 spec). For Altitude, at
start-up, trapezoidal commutation is accomplished using the motor’s Hall Sensors (AD01
11.1.4.1 spec). Automatic switchover to sinusoidal commutation is done once a Hall Sensor
transition index is received. A/B Incremental signals used for ALT motor’s sinusoidal
commutation come from the output of the Heidenhain Interpolator box (IBV 660B). One
interpolator box is used per motor controller. The IBV 660B Interpolator boxes convert the
tape encoder read-head 1Vpp signal into incremental encoder signals with a 25-fold
interpolation factor. This results in approximately 113,650 counts per motor pole pair.