BENSHAW RSi-030-SG-4B, Service Manual

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Description
24 VDC
The fan boards generate 24 VDC from a switch mode power supply on the fan board.
This 24 VDC is sent to the Main SMPS board as 24P1. At the Main SMPS board, the
24P1 is passed through contacts of the fan control relays (RLY2, RLY3, & RLY4) and is
returned to the fan boards as 24P. This 24V (24P) is used to power up to 2 fans per fan
board. The larger horse power VFD’s can have up to 3 fan boards powering up to 2 fans
each from connectors CN3 and CN4.
Operation of the Fan Control Relays is always ON when power is on. See parameters
I/O-84 and I/O-85 for other options.
Fan Fault Monitoring (150 HP and larger)
These fan boards have a fan monitoring circuit which uses an additional signal from the
fans. The fans have 3 wires. The middle wire (pin 2) is a fan fault monitor from each fan.
Look at this as a normally closed switch. The Fan board monitors each fan (pin 2) and
sends each signal to an OR gate. Inputs to the OR are low (zero volts). Output of the OR
gate is low, no faults. This low signal keeps a transistor (part of fan monitor circuit) in
the on state, representing a closed switch out of CN7. All 3 fan boards send this normally
closed signal (CN7) to the Main SMPS board connectors CN8, CN9 & CN15. The
connectors form a series circuit of all 3 fan board inputs.
If either fan (or both) fail, the OR gate input signal is pulled high which outputs a high
from the OR gate. This will turn off the transistor (i.e. open switch) out on CN7. At the
Main SMPS board, if any of the fan board signals (from CN7) open, this interrupts the
series string. The Main SMPS generates a fan lock fault.
Jumpers
When a fan board powers only one fan, the unused connector (CN3 or CN4) must have a
jumper installed to hold the fault signal low. Jumper pins 1 & 2.
At the Main SMPS board, when any one of the 3 connectors (CN8, CN9 or CN15) is not
used, the unused connector must have a jumper installed to maintain the series connection
of all 3 connectors. Jumper pins 1 & 2.
Switch J1 (280/315)
Switch positions are labeled 280 and 315. 280kW is 400 HP (and below), 315kW is 500
HP (and above). The larger HP's (500 and above) have a heat sink thermal switch
plugged into terminal CN18. The smaller HP's do not. The J1 switch position
determines if the thermal switch is monitored or not. The 280 position bypasses the
thermal switch input, the 315 position puts the thermal switch in series with the fan
monitoring connectors, CN8, CN9 & CN15. When the thermal switch opens (90
°
C), the
VFD still trips on a Fan Lock Fault as the thermal switch is part of the Fan Monitoring
circuit.
Pub. # 890046-10-00
Dec. 2015
Section 3, Page 17 of 20