TriPoint VertexRSI 7200, Operation And Maintenance Manual

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O V ERVIE W
2 - 1 2
The Portab l e Ma i ntenance Contro l Un i t (PM C U) l ocated i ns i de the 7 1 5 0 Dr i ve
C ab i net a ll o w s the operator to contro l antenna movement from the prox i m i ty of the
antenna.
The M AIN CIRC UIT BRE A KER contro l s the ma i n po w er to the dr i ve motors, the li m i t
s w i tches, and the dr i ve cab i net, but does not prov i de po w er to the 7 2 0 0 A C U.
Each i nverter has an i nd i v i dua l c i rcu i t breaker for protect i on.
The EMERGEN C Y ST OP s w i tch (on the outs i de of the dr i ve cab i net), w hen pressed,
removes po w er from the dr i ve motors by open i ng the dr i ve enab l e contactor.
The A Z and EL i nverters prov i de pu l se-w i dth-modu l ated motor current, a ll o w i ng
cont i nuous l y var i ab l e dr i ve rates over a range of up to 5 0 to 1.
The 2 4 V D C po w er supp l y prov i des operat i ng vo l tage to the dr i ve cab i net re l ay
c i rcu i t board.
Re l ay PCB accepts a ll li m i t s w i tch status i nputs and contro l s the commands to the
i nverter dr i ves and the POL motors.
2.4.2.1 AZ a nd E L D ri v e I nv e r t e r s
One of the cr i t i ca l advantages of the 7 2 0 0 A C S over many other systems i s the
use of var i ab l e frequency dr i ve i nverters to contro l the speed of standard three-
phase i nduct i on motors for A Z and EL antenna mot i on. Th i s approach has severa l
d i st i nct advantages over the common l y used and s i mp li st i c on/off contactor contro l
of motor po w er. F i rst, i nverters a ll o w V ertex to offer t w o-speed contro l i n a
standard conf i gurat i on w i thout the prob l ems assoc i ated w i th spec i a l dua l -w ound
motors or c l umsy c l utch i ng arrangements. Second l y, the i nverters offer prec i s i on
motor contro l by ramp i ng motor speeds up and do w n i n a contro ll ed manner rather
than s i mp l y s w i tch i ng fu ll motor po w er on and off and hav i ng to contend w i th
i nert i a l coast i ng of the motor rotor and the re l ated ax i s overshoot. In add i t i on to
these t w o d i st i nct advantages, the i nverter dr i ves offer super i or motor protect i on
through soph i st i cated e l ectron i c motor overcurrent protect i on. Motor current i s
cont i nuous l y mon i tored and compared aga i nst a ll o w ab l e l eve l s for d i fferent
cond i t i ons. Shou l d the actua l measured current exceed the a ll o w ab l e l eve l s, the
i nverter tr i ps and the dr i ve i s d i sab l ed. The i nverter then has the capab ili ty to
automat i ca ll y reset and cont i nue operat i on, prov i ded the current rema i ns w i th i n
a ll o w ab l e li m i ts.