Topic ID: id_24368283
Version: 2.0
Date: Nov 7, 2019 8:53:50 PM

Power Distribution Unit Theory

This Cmodule covers NGPDU-6, 60, 61 and NGPDU-7, 70, 71.

This module contains the following sections:

Overview - Overview
NGPDU Physical Description - NGPDU Physical Description
NGPDU Service Overview - NGPDU Service Overview
NGPDU Electrical Specifications - NGPDU Electrical Specifications
NGPDU Drawings - NGPDU Drawings
NGPDU LEDs - NGPDU LEDs
NGPDU Control Board Switches and Fuses - NGPDU Control Board Switches and Fuses

1 Overview

The PDU provides a single location to connect input power for the entire CT system. Its function is to provide the following features to the System:

Provide compensation means for a wide range of input voltages via tap selection
Provide required system AC power from a single source
Provide High Voltage DC power for x-ray generation
Provide power for gantry axial rotation
Provide a means for emergency shutdown of all x-ray and drives power circuits
Provide system AC power circuit protection
Provide an interface for an external UPS connection
Meet the requirements of IEC601 for both radiated and conducted emissions

The PDU is designed to comply with United States Federal Regulations and the European Medical Device Directive. It bears the certification marks of a United States National Recognized Test Laboratory with Canadian deviation or a Canadian certified test house. Each unit is identified as being in compliance by being labeled with the official mark(s) of each respective agency.

While in the stand-by mode, the NGPDU does not generate sound levels in excess of 50dbA, when measured at a distance of one meter from the nearest cabinet surface, in any direction.

2 NGPDU Physical Description

2.1 Mechanical Enclosure

The enclosure has a front, rear and top access covers. The top cover is installed on the frame with a captive fastener in the middle of front edge. The front cover weighs less than 22 lbs (10 kg).

A single full-width Lexan safety shield is provided under the front cover. It extends ½” below the top front edge of the assembly to the bottom of all HVDC Supply components, including the PDU Control Board.

The rear cover is held in place by two captive fasteners. To maintain a good high frequency ground between internal subassemblies, all internal metal surfaces are solidly grounded to each other.

2.2 Component Locations

The main input transformer is located in the rear accessible chamber near the bottom of the cabinet, allowing enough room for cable access beneath. For ease of installation and serviceability the remaining components for the HVDC Supply and AC Power Distribution are located on the vertical dividing panel behind the front cover. Refer to Table 1 below, for general component information. Items numbers in table appear in circles of Figure 1.

Table 1. Major Components
Item	Part No.	Name / Description	Comments
1	2326492-6, 7, 60, 70, 61, 71	NGPDU-6, 7, 60, 70, 61, 71
2	2354578-3	Front Cover	NGPDU-6, 7, 60, 70
2	5434914-2	Front Cover	NGPDU-61, 71
3	2354579-2	Side Cover
4	2354580-2	Rear Cover
5	2354581-2	Top Cover
6	2334820-3	PDU Control Board
7	5324790	125A CB ASSY	CB1
8	5324796	16A Breaker	CB2
8	5324796-2	Circuit Breaker-ABB-S203-D16	NGPDU-61, 71
9	5266344	50A Breaker	CB3
10	5267302	40A Breaker	CB5
11	5324793	20A Breaker	CB7
11	5324793-2	Circuit Breaker-ABB-S202-D20	NGPDU-61, 71
12	5272302	20A Breaker	CB8
12	5272302-2	Circuit Breaker-ABB-S203-D20	NGPDU-61, 71
13	5324756	4A Breaker	CB9, CB10
14	5337228	160A Contactor	Kxg
15	5324792	54A Contactor	Ktg
16	5324762	18-32A Contactor	Ksv, Kcn, KDP
17	5324764	14-25A Contactor	Kss
18	5162052	Adjusted Relay	VMR1,VMR2
19	5324765	200A Fuse	F1-3, NGPDU-6, 60, 61
19	5324766	100A Fuse	F1-3, NGPDU-7, 70, 71
20	5324753	6uf / 370Vac Capacitor	C1-6
21	5324768	4700uf / 450V Capacitor	C7, C8
22	5324770	Diode Bridge	BR1
23	5324776	+24V PS	PS
24	5334050	Resistor Assy	R
25	5344530	Emergency Switch	SW
26	5334049	LED Assy	LED
27	5344531	Real Switch (Gantry Enable Switch)	SW including LED

2.3 Product Labeling

The PDU has a rating plate permanently attached to the rear cover, near the top edge and approximately centered on the cabinet. It contains the following information:

3 NGPDU Service Overview

3.1 Replacement Parts / Interchangeability

All replacement parts required for servicing the PDU are directly interchangeable without need of any re-adjustment. Circuit boards and sub-assemblies are given unique part numbers and revisions are completely backward compatible. Any changes to form, fit, or function which affect interchangeability shall require the assignment of a unique part number.

3.2 Service Tools

The PDU is designed so no special service tools are required. The assembly can be serviced with standard service tools.

4 NGPDU Electrical Specifications

4.1 Primary Input Power

The input power terminals accommodate #4 to #1/0 (fine strand) wire sizes. Ferrules are provided for the maximum wire capacity allowed. Input line fuses are used to protect the system. Dual element, time delay motor starting fuses are used.

4.2 Input Filtering

Low inductance, AC filter capacitors rated for mains connection are installed in a floating wye configuration on the three primary lines, on the load side of the fuses. Each capacitor is rated at 6.0 µF.

4.3 Input Transformer

The main input transformer is an indoor style, multiple winding, 3-phase isolation transformer. It has an open frame, varnish impregnated core & coil construction. It is suitable for continuous duty without requiring forced air-cooling. The insulation system used is UL, CSA, & IEC recognized for 180C (Class H) or better, and each transformer is labeled accordingly.

4.3.1 Magnetic Circuit

The magnetic circuit is designed for nominal 50/60 Hz operation (47 to 63 Hz limits). It accommodates a daily variation of ±10% input voltage, (i.e., 110% input voltage doesn’t cause excessive exciting current and core losses). Under worst case conditions, the transformer’s peak inrush current is less than 1000A when properly connected and energized at 380 V, 50 Hz.

4.3.2 Primary

All power for the CT System passes through the primary winding of the input transformer. It is protected by the primary input fuses described above.

The primary winding is designed for delta connection. Voltage selection taps are provided on each phase to accommodate 20 volt steps over the input voltage range of 380 to 480 V. All leads are brought out to a panel for external voltage selection. Leads are designated as follows:

(For NGPGU-71) The primary winding is designed for delta connection. Voltage selection taps are provided on each phase to accommodate 20 volt steps over the input voltage range of 200 to 240V and 380 to 480 V. All leads are brought out to a panel for external voltage selection. Leads are designated as follows:

Table 2. Compact PDU Primary Taps
3 Phases	Input	200V*	220V*	240V*	380V	400V	420V	440V	460V	480V
Phase 1	1H1	1–6	1–5	1–4	2–6	2–5	2–4	3–6	3–5	3–4
Phase 2	1H2	1–6	1–5	1–4	2–6	2–5	2–4	3–6	3–5	3–4
Phase 3	1H3	1–6	1–5	1–4	2–6	2–5	2–4	3–6	3–5	3–4
Note 1: * is only for NGPDU-71.

The gap in the winding between sections is located at the electrical middle of the winding. This feature allows the use of an alternate connection pattern for 200/220/240 volt input. In this configuration the PDU maximum momentary input rating is limited to 90kVa.

At shipment, the primary taps are set to the 480 volt connection.

4.3.3 Secondary #1 (designated as the “X” winding)

Secondary #1 is a 208Y/120V wye connected power winding. The phase leads are labeled X1, X2, and X3. The neutral, labeled X0, is isolated and brought out for external connection to ground.

The full winding feeds general-purpose power to the CT system. The winding is protected at 50A per phase with a three-pole, 50A circuit breaker labeled CB3.

4.3.4 Secondary #2 (designated as the “Y” winding)

Transformer for Model 2326492-X:

Secondary #2 is a nominal 474Y/274V wye connected power winding. The phase leads are labeled Y1, Y2, and Y3. The neutral, labeled Y0, is isolated and brought out for external connection to ground.

The #2 secondary winding provides x-ray & drives power to the system. The full winding powers the HVDC supply. This is a six-pulse unregulated DC supply, which feeds the X-Ray source. As such, the output current is rich in the non-triplen odd harmonics. In particular, it contains ~35% 5th and ~15% 7th harmonic with additional higher harmonics being substantially lower magnitude.

The 440Y/254V taps feed an external Variable Speed AC Motor Drive. Assuming an 8% duty cycle, this drive produces an effective load current of 4.6A per phase. These taps are to be protected at 16A per phase with a three-pole, 16A circuit breaker, labeled CB2.

4.3.5 Shields

Full width electrostatic shields are provided between the primary and secondary windings. These are made from 0.005” copper or aluminum foil, with a minimum 0.5” insulated overlap. Each shield is grounded to the core and frame with green leads as short as practicable. (The lead position and attachment method minimizes shield impedance to high frequency noise signals.)

4.4 AC Power Distribution

A general overview of the AC Power Distribution of the CT system is shown in the diagram below.

4.5 General Purpose 120/208V AC Power Distribution

4.5.1 Full Winding Protection

The PDU Isolation Transformer, Secondary #1, supplies low voltage AC subsystem power. It is protected at 50A per phase with a three-pole, 50A circuit breaker. The full winding protection breaker is labeled CB3.

4.5.2 UPS Interface

A 10 position terminal strip, labeled TS4, is provided in the bulkhead for connection of an optional partial system UPS. This terminal block has compression type terminals approved for use with bare or stranded wire and is suitable for wire size 8AWG.

Terminals TS4-1 through TS4-5 provide output power connection to the optional UPS. Terminals TS4-6 through TS4-10 provide the power connections back to the NGPDU from the UPS. Connections are as follows:

Table 3. UPS Connection
Terminal Number	Signal Name	Functional Description
1	CB3-A	Phase A, 120VAC power to UPS
2	CB3-B	Phase B, 120VAC power to UPS
3	CB3-C	Phase C, 120VAC power to UPS
4	0VAC	Neutral (0VAC) to UPS
5	GND	Safety ground (G/Y) wire to UPS
6	UPS-A	Phase A, 120VAC power from UPS
7	UPS-B	Phase B, 120VAC power from UPS
8	UPS-C	Phase C, 120VAC power from UPS
9	0VAC	Neutral (0VAC) from UPS
10	GNDC	Safety ground (G/Y) wire from UPS

Jumpers shall connect terminals 1 to 6, 2 to 7, and 3 to 8 with the PDU loads connected to the outputs of terminals 6, 7, & 8. These jumpers will be removed in the field whenever an optional UPS is used with the system.

4.5.3 Circuit Protection

AC power is distributed to the CT System via seven (7) separate branch circuits. These branches are protected by individual circuit breakers as follows:

Table 4. Circuit Breaker
Breaker	Rating	Poles	Phase	Load Description
CB2	16A	3	A B C	Axial Drive
CB5*	40A	3	A B C	CT Gantry Rotating Loads
CB7	20A	2	B C	Operator Console
CB8	20A	3	A B C	R3 Power
CB9	4A	1	A	NGPDU Control Power Supply
CB10	4A	1	C	N/A
*Table service outlet is limited to 10 amperes.

4.5.4 AC Power Output Connections

The output connectors for AC power distribution to external subsystems shall be as follows:

Table 5. AC Output Connectors
Subsystem	PDU Connector Type
Gantry	40A, 3P, 5W Phonix UK16N labeled TS5-4 to 8.
Console	20A, 2P, 3W Phonix UK16N labeled TS5-0 to 3.

4.6 High Voltage DC Power Supply

4.6.1 Electrical Requirements

The HVDC power supply is an unregulated, six pulse DC power source that feeds the high voltage subsystem used to generate x-rays. For model 2326492–X the output voltage of this supply ranges between a maximum of 740VDC (No Load) and a minimum of 480VDC (minimum sag at a maximum step load of 225ADC). For model 2326492-X the output voltage of this supply ranges between a maximum of 760VDC (No Load) and a minimum of 525VDC (minimum sag at a maximum step load of 100ADC).

4.6.2 Circuit Protection

The input to the HVDC Supply is the 3-phase, output from the transformer secondary #2 as previously described. Each phase of this winding is protected by semiconductor fuse, labeled F1, F2, F3. Fuse sizes are indicated below.

For model 2326492-6, 60, 61: F1, F2, F3 = 200 Amp, 690VAC

For model 2326492-7, 70, 71: F1, F2, F3 = 100 Amp, 690VAC

4.6.3 Construction / Description

The load side of the fuses is connected to a three-pole contactor, Kxg, having an AC1 rating of 100 Amps. The load side of the contactor is connected to the input of a 3 phase, full wave bridge rectifier / capacitor filter circuit. An auxiliary contactor, Kss, in series with a 20 ohms / phase resistive soft-start circuit is connected in parallel with the main contacts of Kxg.

EMC Filter Capacitors - C4, C5, C6

Low inductance, AC filter capacitors rated for mains connection are installed in a grounded wye configuration on the load side of Kxg. Each capacitor is rated 6.0 uF and has a minimum operating voltage rating of 330 VAC with a surge voltage rating of at least 2KV. If metal can style capacitors are used, their cans are solidly grounded to chassis metal and they are suitable for 330 VAC line to ground operation.
Bridge Rectifier - BR1

A 3-phase, full wave bridge rectifier rated 200 Amp, 1600V is used. The bridge rectifier is mounted to an aluminum heat sink, approximately 2°± X 6°± X 1/4°±. Aluminum Association Type 1100- F or equivalent aluminum is used. Thermal compound is used between the heat sink and rectifier and between the heat sink and chassis-mounting surface in accordance with the bridge manufacturer's specification.
HVDC Filter Capacitor(s)

The DC output of the bridge rectifier is filtered with two 4700uf, 450 volt electrolytic capacitors connected in series across the output terminals of the bridge. A discharge resistor network for each capacitor is included on the PDU control board.

4.6.4 Output Terminations - TS2

HVDC output leads from the capacitors terminate in a three position terminal block, labeled “TS2”. In addition to the cable ground connection, a cable clamp is provided at the NGPDU bulkhead, which is used for strain relief and 360. termination of the shield of the field installed cable.

Table 6. TS2 Terminal Block
Terminal Number	Signal Name	Functional Description
1	“+”	HVDC to CT gantry.
2	GND	Auxiliary safety ground (G/Y) wire to CT gantry.
3	“-”	HVDC Return to CT gantry.

4.7 Axial Drive Circuit

4.7.1 Electrical Requirements

The 440V taps of secondary #2 are used to power an external variable speed AC motor drive used for axial rotation of the gantry. The drive uses a conventional three-phase full wave bridge rectifier input circuit. This produces strong 5th & 7th harmonic currents typical of 6-pulse rectification. The maximum load under gantry acceleration conditions is 15A.

4.7.2 Circuit Protection

The circuit is protected at 15A per phase with a three-pole, 16A circuit breaker, labeled CB2.

4.7.3 Axial Drive Contactor

The CB2 circuit breaker feeds a three-pole contactor, labeled Ksv. The contactor’s 120VAC coil is controlled externally by the CT system. Auxiliary contacts on the contactor provide status feedback information to the system.

4.7.4 Output Terminations

Output leads from the Ksv contactor terminate in a four position terminal block, labeled TS3. In addition to the cable ground connection, a cable clamp is provided at the NGPDU bulkhead, which is used for strain relief and 360. termination of the shield of the field installed cable.

Table 7. TS3 Terminal Block
Terminal Number	Signal Name	Functional Description
1	Ksv - 440A	Phase A, 440Vac power to Axial Drive.
2	Ksv - 440B	Phase B, 440Vac power to Axial Drive.
3	Ksv - 440C	Phase C, 440Vac power to Axial Drive.
4	GND	Auxiliary safety ground ( G / Y ) wire to Axial Drive.

4.8 Control Signals

The PDU provides all power to the CT system. A PDU Control Board is located within the unit and provides for proper sequencing of the sub-system power, servo system, and x-ray backup contactor when commanded by the system. To facilitate control, the PDU Control Board contains a low voltage limited energy (LVLE) 24Vdc power supply, which provides the necessary communication power to the system. The output voltage of this supply is 24 VDC, ±3 volts for all conditions of line and load.

4.8.1 Subsystem Signal List

The following is a list of PDU Control Signals, that are accessible by means of a 25 position, female subminiature D type receptacle connector located in the output bulkhead. This connector is labeled J1.

Table 8. Subsystem Signal List
Pin #	Signal Name	Functional Description
1	+24V	+24Vdc output to gantry.
2	+24V	Redundant pin +24Vdc connection.
3	GANTRY_PWR-CLSD	+24Vdc output signal from normally open auxiliary contact on the Gantry Power Contactor.
4	ESTP-SRC	+24Vdc output from PDU E-Stop momentary Pushbutton (normally closed) to E-Stop control loop in Gantry.
5	LP-CONT-CLSD	+24Vdc output signal to Gantry from a normally open auxiliary contact on the Axial Servo Power Contactor.
6	XG-CONT-CLSD	+24Vdc output signal to Gantry from a normally open auxiliary contact on the XG Power Contactor.
7	KSS-CONT-CLSD	+24Vdc output signal to Gantry from a normally open auxiliary contact on the XG Soft-Start Contactor.
8	PHASE-LOSS	Latched +24Vdc output signal to Gantry that indicates one or more phases of the 380-480VAC feeding the generator was less than the required minimum voltage.
9	ILK_OPEN	+24Vdc output signal to Gantry that indicates the customer room door interlock is open.
10	BUSS-FLT	Latched +24Vdc output signal to Gantry that indicates the HVDC did not charge to >200V in 200mS.
11	OVER_TEMP	Latched +24Vdc output signal to Gantry that indicates the input transformer has overheated.
12	N/C	(1k pull-down to PGND to prevent floating wire)
13	CHASSIS-GND	Chassis (earth) ground connection for cable shield.
14	PGND	Control power return (PGND) for 24Vdc control circuits to/from gantry. Signal referenced to chassis ground in PDU.
15	PGND	Redundant pin for PGND connection.
16	GANTRY_PWR	Steady-state +24Vdc input signal from the Gantry to close the CT Gantry Power Contactors (KTG).
17	EXP-INTLK	Exposure Interlock current loop from Gantry to PDU. (PDU provides series connection for customer Room Door Interlock between PDU_PGND and this signal.)
18	CLSELOOP	Steady-state +24Vdc input signal from the Gantry to close the Axial Power Contactor (KSV).
19	XG-CONT	Steady-state +24Vdc input signal from the Gantry to close the XG Soft-Start & Power Contactors (KSS & KXG). This signal is serially connected to the thermal switch, which is used to prevent the overheating of discharge resistors on control board when IGBT happen failure.
20	XRAYLITE	Steady-state +24Vdc input signal from the Gantry to close the “X-ray ON” Light relay.
21	SYSLITE	Steady-state +24Vdc input signal from the Gantry to close the “System ON” Light relay.
22	RDYLITE	Steady-state +24Vdc input signal from the Gantry to close the “Generator Ready” Light relay. NGPDU provides isolated terminals for customer Room Light connections.
23	XG_ENBL-CONT	Steady-state +24Vdc input signal from the Gantry to indicate the HVDC Bus is enabled.
24	N/C	(1k pull-down to PGND to prevent floating wire)
25	N/C	(1k pull-down to PGND to prevent floating wire)

4.8.2 Room Warning Light & Door Interlock Connections

A ten position terminal block, labeled TS6, is provided in the output bulkhead for connection of the customer room warning lights and door interlock. This terminal block has compression type terminals approved for use with bare or stranded wire and shall be suitable for a wire size range of 14 to 10AWG (2.25 to 5.5 mm2).

Terminals 1 through 8 are used for connection of external hospital room warning lights as described below. Terminals 9 & 10 are used for connection of a room door interlock switch in the system x-ray enable circuit.

EXTERNAL “XRAY ON” LIGHT - A normally open relay contact rated 125 VAC, 10 Amps is connected between Positions 3 & 4 of the terminal block.
EXTERNAL “SYSTEM ON” LIGHT (Currently this function is not yet available) - A normally open relay contact rated 125 VAC, 10 Amps is connected between Positions 5 & 6 of the terminal block.
EXTERNAL “GENERATOR READY” LIGHT - A normally open relay contact rated 125 VAC, 10 Amps is connected between Positions 7 & 8 of the terminal block.
Positions 2, 4, 6 and 8 of the terminal block are jumpered together. Series RC networks having a resistance of 470 ohms, a capacitance of 0.47 uF and a voltage rating of 250 VAC, are connected across terminal block positions 3 & 4, 5 & 6, and 7 & 8 on the Control Board.
The terminal block is labeled as follows:

In addition, the following information appears near the terminal block:

caution

POTENTIAL FOR ELECTRICAL SHOCK.
TURNING OFF POWER TO THE PDU MAY NOT REMOVE POWER TO THIS TERMINAL BLOCK.
VERIFY REMOVAL OF POWER WITH AN APPROPRIATE MEASURING DEVICE BEFORE SERVICING. INPUT VOLTAGE NOT TO EXCEED 30VAC.

ROOM DOOR INTERLOCK - Positions 9 & 10 of the terminal block provide for a Room Door interlock in the X-Ray Exposure control of the system. Terminal 9 is to be connected to the EXP_INTLK signal (J1-17) and terminal 10 is to be connected to PDU_PGND on the PDU Control Board.
These terminals are clearly labeled “DOOR INTLK SW”.
At shipment from the factory, each NGPDU has a 14 AWG (2.25 mm2) jumper wire installed between terminals 9 & 10.

5 NGPDU Drawings

5.1 Gantry Power Control

When the 120VAC ON signal is received at the GANTRY_PWR connection, given the auxiliary power switch is closed, relay coil KD2 is energized and its contacts close. This relay completes the circuit to the coil of Ktg, which in turn completes the 120VAC circuit to the gantry and table. See Figure 7. Gantry and table power is protected by CB5.

Table and gantry service outlet power is unaffected by 120VAC ON signal and can only be disabled by its associated circuit breaker CB4. Note that CB5 is slaves to master circuit breaker CB3. Table service outlet is limited to 10 amperes.

5.2 Axial Drive Power Control

Axial Drive Power is controlled by relay Ksv and is protected by circuit breaker CB2. When the PDU control board senses an e-stop condition, NGPDU is disconnected with Gantry_PWR_CLSD loop, which prevents activation of the relay Ksv.

5.3 HVDC Supply Control

When the XG-CONT signal is received, the HVDC supply will produce output. When the coils KD4 is energized, the coil Kxg is energized. The contacts on Kxg close and supply power to the HVDC supply. This operation can be inhibited by the PDU control board “E-stop” circuit, through relay contacts Ktg. See Figure 9.

5.4 Console Power Control

120VAC Power for the console is derived from two legs of 208VAC. Console power is protected by circuit breaker CB7. CB7 is a slave to CB3.

5.5 Room Light Control

5.6 E-Stop Control

For the following discussion, see Figure 12.

Normal State

When the GANTRY_PWR signal is received, KTG contractor is closed, +24V DC output is given from PDU E-stop button (normally closed) to E-stop control loop in Gantry.
E-Stop

When an E-stop switch is activated, the connection between 24V and ESTP_SRC is opened, ESTP_SRC voltage dropped to 0V DC.

6 NGPDU LEDs

There are 17 LEDs on the PDU Control Board. See Figure 13.

The ON / OFF status of these LEDs are explained in the below table:

Table 9. LED Description
LED on Control Bd		Description		Error
ID	NAME	ON	OFF	Error
DSD1	Voltage Fault	It’s for HVDC - If the differential buss voltage exceeds 500Vdc within the first 200mS after turning on the PDU Control board, control board shall detect and latch a VFLT condition and shall issue a “VFLT”.i.e. DSD1 light.	If the contactors Kxg and/or Kss are closed, the control board should not have this issue.i.e. DSD1 OFF.	DSD1 LED ON (RED)
DSD2	BUSS Fault	It’s for HVDC - If the differential buss voltage does not exceed 200Vdc within the first 200mS after turning on the PDU Control board, control board shall detect and latch a BS_FLT condition and shall issue a “BUSS_FLT”. i.e. DSD2 light.	If the contactors Kxg and/or Kss are closed, the control board shall open them,i.e. DSD2 OFF.	DSD2 LED ON (RED)
DSD3	RDY light	This is the “Generator Ready” Light. NGPDU provides isolated terminals KD7 for customer Room Light connections.	This means the “Generator is not ready.”.	DSD3 LED OFF (GREEN)
DSD4	X-ray light	From the Gantry to close the “X-Ray ON” Light. NGPDU provides isolated terminals KD7 for customer Room Light connections.	This means the X-ray shouldn’t be ON from Gantry signal.	DSD4 LED OFF (GREEN)
DSD5	SYS light	Input signal from the Gantry to close the “System ON” Light relay. NGPDU provides isolated terminals KD5 for customer Room Light connections.	System OFF	DSD5 LED OFF (GREEN)
DSB1	HV-	Has HVDC-	No HVDC-	DSB1 LED OFF (YELLOW)
DSB2	HV+	Has HVDC+	No HVDC+	DSB2 LED OFF (YELLOW)
DCEN1	DC Enable	If the contactors Kxg and/or Kss are not closed, and there is no issue, DCEN1 is on.	If the contactor Kxg and/or Kss are closed, and there is no issue, DCEN1 is off.	DCEN1 LED OFF (Green)
GRN1	Voltage +24V	24VDC green status indicator lamp - it will be ON whenever the NGPDU is energized.	24VDC green status indicator lamp --it will be OFF whenever the NGPDU is powered off.	GRN1 LED OFF (Green)
DL1	Phase Loss	A phase under-voltage / open fuse detection circuit on the PDU Control board. If the voltage w.r.t. ground on any one or more phases drops below 185Vac (~70% of the normal), DL1 light.	If contactors Kxg and/or Kss (described above) are closed, no phase loss issue.	DL1 LED ON (RED)
RED	Interlock Open	This is +24Vdc output signal to Gantry that indicates the customer room door interlock is open. This signal automatically resets and dynamically tracks the status of the interlock circuit.	It means no interlock happens.	interlock LED ON (RED)
KC1	Relay LED	Over temperature protect status	Not over temperature protect or less than 30s	LED ON(RED)
KC2	Relay LED	Over temperature protect status	Not over temperature protect	LED ON(RED)
KD1	Relay LED	Ktg Power ON	Ktg Power OFF	LED OFF (Green)
KD2	Relay LED	ksv Power ON	Ksv Power OFF	LED OFF (Green)
KD3	Relay LED	Kss Power ON	Kss Power OFF	LED OFF (Green)
KD4	Relay LED	Kxg Power ON	Kxg Power OFF	LED OFF (Green)

7 NGPDU Control Board Switches and Fuses

Table 10. NGPDU Control Board Switches and Fuses
SWITCH	NAME	POSITION	DESCRIPTION
SW 1	Reset	pressed	clear all warning LED, control board goes to normal active state.
		not pressed	normal active state.
SW 2	MNL HVDC	AUTO(OFF)	normal active state.
		MAN(ON)	Manually turns HVDC on. Bypasses firmware HVDC control. Gantry 120 VAC must be "on" and HVDC Enabled at service switch board for HVDC to be present at gantry. (See NOTE)

FUSE	NAME	RATING	DESCRIPTION
1	FC10A	6A250VAC	fuse of the external light (SYSLIFT,RDYLITE,XRAYLITE)

note:

The SW2-MNL_HVDC switch is set to the AUTO OFF position from the factory and must always remain in the AUTO OFF position.

No service procedure requires the use of this switch.
This switch should never be tampered with by Field personnel for any reason including troubleshooting NGPDU problems unless explicitly directed to do so by CT Engineering.